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  • Chromatographie, Gas  (67)
  • 42.55  (64)
  • Phytochrome  (56)
  • Springer  (187)
  • Periodicals Archive Online (PAO)
  • 1975-1979  (187)
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  • Springer  (187)
  • Periodicals Archive Online (PAO)
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  • 1
    ISSN: 1432-0630
    Keywords: 42.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Lasing in atomic lines of noble gases and fluorine, prior to excimer radiation, was observed in an electric discharge ArF/XeF excimer laser. Some Ar/Xe lines end at metastable levels, which are very important for the formation of ArF/XeF excimer molecules. Five new lasing lines of atomic fluorine have been obtained. Consideration is given to the use of lasing in atomic and molecular lines, that occurs in one burst, in investigations of the excitation kinetics of excimer states under the conditions of a high-pressure electric discharge.
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  • 2
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    Applied physics 14 (1977), S. 277-282 
    ISSN: 1432-0630
    Keywords: 42.55 ; 52
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The paper deals with the properties andI-V characteristics of discharges in narrow capillaries used, for example, for He−Ne waveguide lasers. It has been observed that discharges in He−Ne waveguide lasers are unstable because of the strongly falling characteristic. A theory is presented which assumes that at low currents wall charges restrict the positive column to a narrow plasma channel and are the main reason for the observed falling characteristic. A numerical evaluation for helium gives results which agree well with experimental data.
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  • 3
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    Applied physics 18 (1979), S. 333-338 
    ISSN: 1432-0630
    Keywords: 87 ; 42.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Energy transfer in DNA-dye-complexes after excitation in the UV down to 220 nm by means of a tunable laser was investigated. DNA of different base composition and polynucleotides were compared. The dyes proflavine, acridine orange and ethidium bromide were used. The energy transfer from DNA-bases to dye molecules was measured in dependence of the excitation wavelength and the base composition of the DNA. Models of the energy transfer from DNA to dye and of the molecular structures of the DNA-dye-complex (intercalation) could be deduced.
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  • 4
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    Applied physics 19 (1979), S. 47-51 
    ISSN: 1432-0630
    Keywords: 42.55 ; 42.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The possibility of building free-electron lasers and masers with quasi-circular undulators is considered. The two-mirror cavity is replaced by a suitable waveguide. The magnetic field along the orbit has a continuous component superimposed on the alternating one. Besides allowing large freedom for electron guiding and focusing, the structure allows effective negative mass conditions, which may enhance the electron beam modulation when space charge effect are important. Furthermore the radiation frequency can be higher than that in a linear undulator with the same electron energy, and long interaction times are possible in a compact structure.
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  • 5
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    Applied physics 19 (1979), S. 345-351 
    ISSN: 1432-0630
    Keywords: 78.55 ; 42.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract PrP5O14, PrxLa1−xP5O14, and PrxY1−xP5O14 (0≦x≦1) single crystals of laser quality were synthesized and their crystallographic and optical parameters measured. Laser emissions in the visible (λ=637.4 nm) with no mirrors in place (superradiance) and also in various optical resonators have been observed.
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  • 6
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    Applied physics 13 (1977), S. 97-99 
    ISSN: 1432-0630
    Keywords: 42.55 ; 82.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract First cw laser oscillation with thresholds below 1 mW was observed for various B1Пu → X1 ∑ g + transitions of diatomic molecular sodium excited by different argon laser lines in the range of 454–488 nm. For pump powers of 0.5 W output powers up to 3 mW and single-pass gain up to 0.1 cm−1 were obtained. Some properties of the heat pipe laser system are discussed.
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  • 7
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    Applied physics 13 (1977), S. 383-385 
    ISSN: 1432-0630
    Keywords: 42.55 ; 42.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract An optically pumped FIR laser was operated with a copper mesh Fabr-Perot output coupler. With this device a Gaussian output beam was obtained andthe degree of coupling could be varied continuously, thus allowing optimum coupling. From the measured properties of the wire mesches grains of two FIR laser lines are calculated and the saturation intensities estimated.
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  • 8
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    Applied physics 14 (1977), S. 25-28 
    ISSN: 1432-0630
    Keywords: 42.55 ; 42.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A new device for magnetically displacing the output mirror of a laser resonator and synchronously tilting an etalon in order to obtain single-mode tuning of a dye laser over a tuning range of at least 10 GHz is described. Comparatively large displacements with good linearity of a coil mounted on a membrane and placed inside the strong magnetic field of a ring magnet are obtained for currents in the order of several hundred milliamperes. Together with etalon flats of appropriate thickness and reflection mounted in the resonator of the laser a versatile instrument for application in intra and extra cavity spectroscopy has been developed.
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  • 9
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    Applied physics 14 (1977), S. 393-398 
    ISSN: 1432-0630
    Keywords: 34 ; 42.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A flowing afterglow method has been used to study a number of reactions of importance in KrF lasers using NF3 as the fluorine donor. Total rate constants are reported for Kr*(3 P 2)+NF3 and Kr++NF3. The thermal energy attachment coefficient has been measured for NF3 and the cross section for the electron excitation process Kr*(3 P 2) +e→Kr*(3 P 1)+e has been estimated. The relevance of these results to discharge pumped KrF lasers is discussed.
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  • 10
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    Applied physics 14 (1977), S. 193-197 
    ISSN: 1432-0630
    Keywords: 42.55 ; 52
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Planar and cylindrical discharges for argon lasers are compared by plasmatheoretical calculations. The maximum laser output power available in the two arrangements is computed in dependence of various parameters neglecting saturation mechanisms. A transverse discharge arrangement confining the positive column by two parallel walls is described and experimental laser threshold values for the current and pressure are reported.
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  • 11
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    Applied physics 14 (1977), S. 255-268 
    ISSN: 1432-0630
    Keywords: 42.80 ; 42.55 ; 85.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract GaAs double heterostructure semiconductor injection lasers which now exhibit more than 25000 h cw room temperature lifetime are of great interest for future use as directly modulated transmitters for high bit-rate fiber optical communications. The effects limiting this application are modulation distortions, spectral width and additional spectral broadening in the case of modulation and spontaneous fluctuations of the output power. The dynamic and spectral behavior of injection lasers, the methods of high bit-rate modulation and the improvement of the high bit-rate modulation capability by coupling two lasers are discussed.
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  • 12
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    Applied physics 15 (1978), S. 185-190 
    ISSN: 1432-0630
    Keywords: 42.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Electron energy loss studies of POPOP andp-terphenyl in the vapor phase at an incident electron energy of 25 eV have been performed. The spectra covering an energy loss between 0 and 9 eV revealed a considerable initial triplet population under electron impact excitation. The implications for electron-beam pumped vapor phase dye lasers are discussed.
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  • 13
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    Applied physics 15 (1978), S. 229-232 
    ISSN: 1432-0630
    Keywords: 42.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A new type of discharge tube for high-power argon-ion lasers constructed of a segmented metal-ceramic compound system is described. Up to date, the system has been operating for 1500 h without failure. The maximum cw output is 140 W, limited by the destruction of the mirrors.
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  • 14
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    Applied physics 15 (1978), S. 439-450 
    ISSN: 1432-0630
    Keywords: 42.55 ; 42.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A theoretical model for the ultrashort-pulse (USP) generation by lasers with saturable absorbers is presented. The gain medium is assumed to be a two-level system whereas the absorber is described by a four-level system which is characterized by a two-stage absorption process and the pertinent relaxation times. Laser dynamical equations are developed in the rate-equation approximation and boundary conditions appropriate for an unidirectional ring cavity are established. Evolution of USP is investigated for different combinations of parameter values appropriate for solid-state laser systems by computer simulation, employing a finite difference approximation for the dynamical equations. It is shown that USP output is attainable even if the cross-section of the excited-state absorption isgreater than that of the ground-state absorption and the laser is operating just above threshold. In fact, it is found that through the participation of a strong excited-state absorption the discrimination against satellite pulses is enhanced so that single-pulse output is more achievable. Furthermore, it is proposed that single picosecond pulses may be obtainable from relatively broad initial peaks by utilizing the high pulse-selection and pulse-shortening efficiency of the absorber due to the contribution of the excited-state absorption. The applicability of the present model to singlet-triplet crossing and photoisomer formation is also discussed.
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  • 15
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    Applied physics 16 (1978), S. 297-301 
    ISSN: 1432-0630
    Keywords: 42.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A grating-tuned cw dye laser with an emission bandwidth of less than 1 GHz and output power in excess of 400 mW has been constructed. This was accomplished using a newly developed holographic grating with sinusoidal groove profile, which resulted in an enhanced spectral efficiency up to 94%. The low losses and the broad spectral working range (more than 1000 Å) which can be easily covered by simple rotation make these gratings an attractive single-stage tuning element for low-gain cw lasers.
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  • 16
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    Applied physics 16 (1978), S. 151-154 
    ISSN: 1432-0630
    Keywords: 42.65 ; 42.55 ; 33
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We observed tunable UV radiation down to 175 nm by SRS of the output of a frequency-doubled dye laser in H2. The high power output of the 4th anti-Stokes to 5th Stokes line generated by the frequency doubled dye laser and the 8th anti-Stokes to 3rd Stokes line generated by the undoubled dye laser represents a broadly tunable coherent radiation source between 189 nm and 2064 nm.
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  • 17
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    Applied physics 13 (1977), S. 109-110 
    ISSN: 1432-0630
    Keywords: 42.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A simple technique is described that allows the generation of a short pulses (1 ns) from dye lasers pumped by a much longer (7 ns) N2-laser pulse. Dye-laser pulses, either with a narrow bandwidth or a short duration, can thus be obtained with the same N2-laser pump.
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  • 18
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    Applied physics 17 (1978), S. 367-370 
    ISSN: 1432-0630
    Keywords: 42.55 ; 78.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We report on room temperature quasi-cw laser action in K5Nd(MoO4)4 at a wavelength of 1.067 μm. The crystal was pumped with the 5140 Å line of an argon ion laser. Due to thermal effects actual cw lasing was not possible. Chopping the pump light with a low duty cycle of 1∶1000 leads to quasi-cw laser action and stable output power. We have determined the fundamental laser parameters: threshold pump powerA T=15 mW, slope efficiency η=22%, and internal lossesL=2.5%. In order to explain the measured relaxation oscillations, diffusion of the excited 4f-excitons is considered. According to a recently developed theory, a diffusion constant ofD=2×10−6cm2/s explains the observed results.
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  • 19
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    Applied physics 14 (1977), S. 121-122 
    ISSN: 1432-0630
    Keywords: 42.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Frequency-tunable generation by means of F 2 + and F 2 − colour centers in a LiF crystal is reported. Colour centers were created by illuminating LiF crystals with electrons of 3 meV energy at the electron current density of 1 μA/cm2. The pumping source was a ruby laser with a peak power of 20 MW, a pulse duration of 20 ns, and a repetition rate of 1 Hz. The frequency tuning is obtained in the range of 0.88–1.25 μm. Discussed are the ways of pumping of colour centers and the possibility of lasing in the spectral region of 0.85 to 2 μm in the type of colour centers under investigation.
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  • 20
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    Applied physics 18 (1979), S. 257-260 
    ISSN: 1432-0630
    Keywords: 32 ; 42.55
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We have demonstrated the feasibility of Doppler-free polarization spectroscopy with a train of ultrashort pulses from a synchronously pumped mode-locked dye laser. The sensitivity of the method is compared with saturation spectroscopy with a single-mode laser.
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  • 21
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    Applied physics 15 (1978), S. 191-196 
    ISSN: 1432-0630
    Keywords: 42.55
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    Notes: Abstract A guideline for the optimum design of linear wall-ablation lamps is presented with a simple empirical formula which describes the luminescent characteristics of lamps. The absolute luminescent efficiency of the wall-ablation lamp was measured. A high-energy dye laser with a quadruple-elliptical cylindrical cavity was constructed using these lamps, and an output energy of 23.3 J (11.6 MW) was obtained with an overall efficiency of 0.31 %. The energy-flow diagram of this laser system was computed with a rate-equation analysis, and the conversion efficiency from electrical input to laser output was determined. One can expect an overall efficiency of about 2 %.
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  • 22
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    Applied physics 17 (1978), S. 181-187 
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    Keywords: 42.55
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A complete theoretical model for optically pumped dye lasers is studied using the rate equation approach which includes excited singlet and triplet state absorption effects. Closed-form solutions under steady-state conditions reveal a novel nonlinear threshold phenomenon: partial reabsorption of the excited laser light can lead to a discontinuous onset of laser oscillation above laser threshold. Theoretical and experimental results for a transversely and longitudinally pumped rhodamine 6G laser are presented in terms of softmode and hardmode behavior at threshold.
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  • 23
    ISSN: 1432-0630
    Keywords: 33 ; 42.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The characteristics of a stable, external-resonator spin-flip Raman laser (SFRL), pumped by a cw carbon monoxide laser of controlled mode quality and spectral content, are determined using a combination of molecular spectroscopy, Raman amplifier and confocal Fabry-Perot interferometer measurements, and heterodyne detection. Single-frequency output of a free-running external-resonator is demonstrated with an inherent linewidth of 〈10 kHz and a short-term frequency jitter of ≃100 kHz. With the resonator length actively controlled to lock an axial mode frequency to the peak of the spontaneous gain, the linewidth of the SFRL output was maintained below 2 MHz. In this mode of operation, small variations in the output tuning rate, corresponding to the magnetic field dependence of the conduction-electrong-factor, were calibrated. Molecular absorption spectra obtained using gas cells both inside and outside the resonator have been used to illustrate the high resolution, wide-range tuning capability and sensitivity of the system. Lambda-doubling of the $$^2 \pi _{3/2} $$ of the Q-branch head of nitric oxide was measured for values ofJ down to 13/2, below which the splitting is less than the Doppler width. The splittings agreed with predictions using parameters obtained by conventional spectra for higherJ-values.
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  • 24
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    Applied physics 19 (1979), S. 241-242 
    ISSN: 1432-0630
    Keywords: 33 ; 42.55
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Several new laser lines using optically pumped deuterated methanol molecules have been discovered. These not only increase the spectral coverage of pumped methanol isotopes but may assist in the assignment of a molecular structure.
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  • 25
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    Applied physics 19 (1979), S. 399-403 
    ISSN: 1432-0630
    Keywords: 42.55
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The selection of a single longitudinal mode of a dye laser can be achieved with double or triple Michelson reflectors instead of Fabry-Perot etalons inside the laser cavity. These systems can be adapted to commercial multimode dye lasers. They provide a high efficiency and a good geometrical quality of the output beam. With a 7 watt pump power (λ=514.5 nm line of the Ar+ laser), a tunable output power of 1 watt was obtained at the peak of R6G, in the main output beam; the total single-mode power, including the auxiliary output beams, exceeded 1.4 watt. These results correspond to efficiencies of 14% and 20%, respectively (24% and 30% slope efficiencies). We discuss in the text why these efficiencies are comparable to those of ring lasers. In the infrared, with a 4.5 watt pump power (red lines of a Kr+ laser), 250 mW of single-mode output power in the main output beam was obtained at 780 nm with Oxazine 750.
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  • 26
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    Applied physics 19 (1979), S. 427-429 
    ISSN: 1432-0630
    Keywords: 33 ; 35 ; 42.55
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    Notes: Abstract Spectral coincidences between CO-laser lines and NO fundamental absorption lines were reinvestigated in order to resolve discrepancies between recently published papers. The absorption of CO laser radiation by NO and NO/Ar mixtures was measured and fitted by calculations using a Voigt profile for the NO line shapes. A new coincidence with a frequency offset of less than the NO Doppler width was found.
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  • 27
    ISSN: 1432-0630
    Keywords: 07 ; 42.55
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    Notes: Abstract A liquid-nitrogen cooled12C16O laser was operated both Q-switched and cw. A total of 276 lasing transitions were observed in cw using an intracavity grating for line selection. In the Q-switch mode, 230 lines occurred without dispersive element in the cavity.
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  • 28
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    Applied physics 18 (1979), S. 235-241 
    ISSN: 1432-0630
    Keywords: 42.65C ; 42.55 ; 33.20
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    Notes: Abstract Design and performance characteristics of a tunable ir waveguide Raman laser pumped by a high power dye laser are described. Using SRS up to third Stokes order in compressed H2, the wavelength range from 0.7 to 7 μm has been covered without gaps. Taking advantage of a waveguide structure in the scattering chamber, energy conversion efficiencies better than 1% with power levels in excess of 80 kW for the third Stokes component have been achieved. The experimental results support the theoretical predictions that a 4-wave parametric process is responsible for the production of the third Stokes component.
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  • 29
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    Applied physics 20 (1979), S. 41-50 
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    Keywords: 41 ; 42.55 ; 95
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    Notes: Abstract The interaction of free electrons and free electromagnetic radiation, in the presence of a uniform magnetic field, can result in stimulated emission or absorption. We analyze the dynamics of single electrons by solving the classical, relativistic Lorentz force equations of motion in these combined fields. An electron may gain energy from, or lose energy to, the radiation field, depending crucially on the phase and oscillation frequency of the electron's helical motion within the superposed, circularly polarized light wave. To first order in the radiation field strength, electrons in a monoenergetic, uniformly distributed beam become spatially bunched, but there is no net energy change. To second order, however, the beam may experience a gain or loss of energy, corresponding to attenuation or amplification of radiation. We compare the bunching of this laser process to the bunching processes involved in 1) the Stanford free-electron laser and 2) the cyclotron maser, and find significant differences in each case. Our analytic results provide a clear, simple picture of the interaction process, and can be useful in exploring light amplification in astrophysical magnetic fields, the magnetosphere, or in laboratory devices.
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  • 30
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    Applied physics 20 (1979), S. 61-65 
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    Notes: Abstract We show that a laser can efficiently accelerate charged particles if a magnetic field is introduced to improve the coupling between the particle and the wave. Solving the relativistic equations of motion for an electron in a uniform magnetic field and superposed, circularly polarized electromagnetic wave, we find that in energy-position phase space an electron traces out a curtate cycloid: it alternately gains and loses energy. If, however, the parameters are chosen so that the electron's oscillations in the two fields are resonant, it will continually accelerate or decelerate depending on its initial position within a wavelength of light. A laboratory accelerator operating under these resonant conditions appears attractive: in a magnetic field of 105 Gauss, and the fields of a 5×1012 W, 10 μm wavelength laser, an optimally positioned electron would accelerate to 700 MeV in only 10m.
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  • 31
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    Applied physics 20 (1979), S. 97-99 
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    Notes: Abstract A narrow-band tunable double-wavelength dye laser with a bandwidth of 0.1 cm−1 is described. The output at one of the wavelengths is found to be completely linearly polarized in the plane of incidence.
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  • 32
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    Applied physics 13 (1977), S. 107-108 
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    Notes: Abstract Intense laser oscillation has been observed from ArF molecules at 1933 Å. Excitation of the gas mixture NF3:Ar:He=1:55:630 at total pressures above 2.1 atm was produced by a transverse electric discharge. The range of fine tuning was from 1927 Å to 1936 Å. An output energy of 0.8 mJ was measured from a laser pulse 15 ns in duration.
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  • 33
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    Applied physics 17 (1978), S. 257-267 
    ISSN: 1432-0630
    Keywords: 42.55 ; 32.60
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    Notes: Abstract The effect of transversally applied magnetic fields on the polarization behavior of a single-mode gas laser is theoretically investigated, stressing the importance of the additivity of respective contributions influencing the time evolution of polarization parameters. By adding a new element to the existing theory, namely the contribution of magnetic-field-free regions in the active medium, and by considering the relatively large effects that small cavity anisotropies can cause, several apparent discrepancies between experiments and existing theory are resolved.
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    Applied physics 15 (1978), S. 59-63 
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    Notes: Abstract Feedback controlled self-excitation of optical pulses of nanosecond duration has been observed to occur rather reliably in a CW dye ring laser, oscillating in a traveling mode. These observations are described analytically by means of a direct time domain approach. It is shown that a steady-state Gaussian pulse whose time duration determined from the self consistency condition in terms of system characteristics describes accurately the observed pulse behaviors.
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  • 35
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    Applied physics 19 (1979), S. 39-41 
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    Notes: Abstract It is shown that when a distributed feedback dye laser is used to generate a train of picosecond pulses, the narrow lines observed in the spectrum are not longitudinal modes, but are due to the intrapulse refractive index changes caused by the heating effect of the pumping pulse.
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  • 36
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    Applied physics 18 (1979), S. 415-419 
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    Notes: Abstract Remarkable intensity fluctuations were observed in the LiNdP4O12 (LNP) laser by placing a moving ground-glass plate across the ouput beam. Resonance-like behaviors were also observed by tuning the moving velocity of the ground-glass plate, with respect to relaxation oscillations. Classical rate equations including the modulation term were given to explain the observed phenomena. Similar intensity fluctuations corresponding to relaxation oscillations were observed when the LNP laser light beam was coupled to an optical fiber.
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  • 37
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    Applied physics 19 (1979), S. 35-37 
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    Notes: Abstract Results of an investigation of 19 organic dyes pumped by a 1.7 MW discharge-pumped XeCl excimer laser are reported. The dye-laser emission covered a wide wavelength range from 340 nm to 710 nm.P-terphenyl shows efficient laser action. The highest energy conversion efficiency exceeds 40% in visible region. In comparison with 250 kW nitrogen laser pumping, higher efficiencies are obtained for most of these dyes in the same dye-laser configuration.
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  • 38
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    Applied physics 19 (1979), S. 185-189 
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    Notes: Abstract We have studied the interaction of stimulated spin-flip Raman scattering and stimulated recombination radiation in n-InSb using a CW CO pump laser. A change in linewidth and output power of second Stokes spin-flip radiation is observed when the tuning curve of the first Stokes stimulated spin-flip radiation and the stimulated recombination radiation cross. The observations are explained using a simple rate equation model.
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  • 39
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    Applied physics 18 (1979), S. 77-80 
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    Notes: Abstract We report, for the first time, on room temperature cw laser action of NdP5O14 and NdAl3(BO3)4 at 1.3 μm wavelength. The emission cross sections of the transition4 F 3/2→4 I 13/2 are 0.24·10−19 cm2 and 1.74·10−19 cm2, respectively. The lowest observed threshold was 45 mW and the slope efficiency was nearly 10%. The minimum threshold is expected to be about 5 mW of absorbed pump light for both materials.
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  • 40
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    Notes: Abstract Laser induced nonlinear absorption profiles in a three-level system have been recorded to study the effect of elastic collisions upon optical coherences. In our particular system, the signal is due to a pure double-quantum term, where we have separated the effect of phase-interrupting collisions from the effect of velocity-changing collisions. Experimental results show that the effect of velocity-changing collisions is very small, and that broadening of the signal is due to phase-interrupting collisions mainly. We are able to determine the increase of the decay rate of the coherent superposition (the “coherence”) of two levels of same parity [Dγ 13/dp=(6.5±1) MHz/Torr] and an upper limit for the mean velocity change (ũ≲5m/s).
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  • 41
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    Applied physics 19 (1979), S. 165-170 
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    Notes: Abstract Computer calculations of ETDL performance indicate that dye laser output can be manipulated by an appropriate choice of a donor (absorber)-acceptor (dye) couple. Studies of relevant laser induced inter- and intramolecular energy transfer processes are presented.
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  • 42
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    Applied physics 19 (1979), S. 221-224 
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    Keywords: 42.10 ; 42.55 ; 42.65
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    Notes: Abstract Wave front of a light pulse is shown to be unstable as it propagates through a resonant saturable absorber, if its frequency is higher than the resonance frequency of the absorber. When ΔωT 2∼1, a small-scale transverse instability with the dimension of (λl abs)1/2 grows rapidly. Its growth-rate is of the order of the small-signal-absorption length of the medium.
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  • 43
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    Applied physics 19 (1979), S. 257-264 
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    Notes: Abstract Employing injection-locking techniques an oscillator configuration was found comprising in a simple way all the features required for fusion directed high-power CO2 laser systems. The oscillator provides emission in single axial modes on rotational transitions which can be freely selected by feeding fluencies of a few mW/cm2 at the particular transition into the oscillator cavity. In the same way simultaneous emission on selectable lines can be achieved. By the same principle the oscillator can be forced to emit in any orientation of polarization. The set up is relatively simple, the alignment rather uncritical, and the operation reliable. Gaussian-shaped nanosecond pulses with low forepulse power are produced with the help of a pulse cutter and saturable multiline absorber. The set up is described and its features are demonstrated by measurements.
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  • 44
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    Applied physics 13 (1977), S. 1-3 
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    Notes: Abstract Disappearance of NF3 and appearance of NF2 and N2F2 in an excimer laser is followed quantitatively with a mass spectrometer. A model for the kinetics is presented.
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  • 45
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    Applied physics 13 (1977), S. 55-58 
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    Notes: Abstract NdxLa1−xP5O14 (0.25≦x≦1) single crystals, placed within a confocal optical resonator, were pumped with ruby laser fundamental and second-harmonic nanosecond pulses. In both cases laser oscillations at 1.05 μm exceeding in duration many times the pumping pulse were obtained.
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  • 46
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    Applied physics 14 (1977), S. 343-350 
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    Notes: Abstract By means of nonlinear absorption spectroscopy data necessary for the interpretation of molecular spectra can be obtained in such spectral regions, where conventional spectroscopic methods yield only a quasi-continuous absorption curve. Using a Zeeman-tuned He−Ne laser at the wavelength of 3.39μm we have measured significant differences in the intensity and temperature behaviour for several ethane absorption lines, the analysis of which made possible a preliminary qualitative assignment of these lines.
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  • 47
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    Applied physics 14 (1977), S. 377-380 
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    Notes: Abstract Due to spatial hole burning, standing-wave dye lasers require a large amount of selectivity inside the cavity for single-mode operation. The output power of these lasers is limited by losses caused by the frequency selecting elements. In a travelling-wave laser, on the other hand, spatial hole burning does not exist, thereby eliminating the need for high selectivity. A travelling-wave cw dye laser was realized by unidirectional operation of a ring laser, yielding single mode output powers of 1.2 W at 595 nm and of 55 mW in the UV-region with intracavity frequency doubling.
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  • 48
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    Applied physics 15 (1978), S. 265-270 
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    Notes: Abstract For a homogeneously broadened two-level ring laser model the stability of the cw laser oscillation in the presence of a passive medium is investigated. The passive material is treated similar to the active material, but without an external pumping mechanism. Stable and unstable regions are shown for various parameters. The stability region of the cw solution becomes extremly small for certain parameters.
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  • 49
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    Applied physics 16 (1978), S. 155-158 
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    Keywords: 42.55 ; 78.60 ; 85.60
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    Notes: Abstract Dynamic characteristics of laser diodes are numerically calculated on multi-mode rate equations, including spatial relaxing interaction causing mode competitions or jumps. It is revealed that the interaction effect is classified into three cases [“independent (or inhomogeneous)”, “competition (or intermediate)”, and “monopoly (or ideally homogeneous)”], that an optimum relaxing coefficient value exists to minimize relaxation oscillations in rise and decay transients, and that the optimum value is related to the relaxation period. Calculated results are discussed in comparison with the experimental results.
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  • 50
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    Notes: Abstract The room temperature cw oscillation at 1.05 and 1.32 μm of lithium neodymium tetraphosphate [LiNd(PO3)4, LNP] lasers in an external resonator and, for the first time, also in a Fabry-Perot resonator with directly applied mirrors is reported. The growth and fluorescence properties of the LNP crystals are briefly described. Laser parameters such as threshold pump power, output power, differential efficiency, optical gain, emission cross section and laser modes are both measured and calculated. Laser experiments show the threshold pump power to be lower for 1.05 μm than for 1.32 μm emission because of the smaller emission cross section; the pump power density is lower for the external resonator than for the Fabry-Perot resonator because of its higher mode losses.
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  • 51
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    Applied physics 14 (1977), S. 199-203 
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    Keywords: 42.55 ; 82.50
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    Notes: Abstract Loss of gain in a dye medium as a result of decomposition by pump photons is considered in terms of disappearance of dye molecules and the appearance of a new, single chemical product having absorption in the fluorescence band. The cases of small signal gain and saturated gain are applied to a single pass through a transversely excited amplifier. Loss of output, defined as “quantum yield of laser deterioration”,Q L , is related to the true quantum yield of molecular destruction of the dye,Q M , and other known parameters. For the experimentally common, saturated gain condition, the smallestQ L can be isQ M , which requires a photochemically bleachable dye with high gain, preferably at high concentration, in a long cavity, operating at high injection and pumping fluxes. Reversing these conditions, the highest valueQ L can be, compared withQ M , is unrestricted.
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  • 52
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    Applied physics 17 (1978), S. 303-307 
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    Notes: Abstract A new and simple technique for measuring the effective diameter of a laser beam used in material processing is described. The time for the temperature of a spot heated by the laser beam to rise to 90% of equilibrium is compared with that predicted theoretically for a Gaussian TEM00 laser beam. A Gaussian beam diameter equivalent is thus deduced. This calculated diameter is of particular relevance to applications where the laser is used as a heat source.
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  • 53
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    Applied physics 17 (1978), S. 393-400 
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    Notes: Abstract Stimulated Raman scattering by polaritons when employing a nonlinear crystal inside the cavity of the laser with Q-switching and locked to fundamental frequency was theoretically studied. The equations were formulated describing the dynamics of the fundamental, Stokes and polariton waves under the assumption of instant Q-switching and uniformity of radiation except in the longitudinal direction. Numerical solutions of the equations were found and analysed. We demonstrate the influence, on generation characteristics, of the most important parameters, such as the effective nonlinearity, the initial level of population inversion, the feedback of the Stokes wave and the group mismatch between a Stokes and a pump wave. Optimum generation conditions are determined. Possibilities of the method are discussed for the generation of a) giant pulses which are controllable with regard to carrier frequency and duration but are unachievable with other methods, b) Stokes pulses of very small duration and high energy having sharp trailing edges, and c) analogous polariton pulses in the middle and far infrared range. The generation using a number of polariton branches in LiNbO3 was considered as an example. Calculations are in qualitative agreement with experimental data.
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  • 54
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    Applied physics 17 (1978), S. 211-232 
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    Notes: Abstract Physical principles, new ways and means of creation, schemes, characteristics and features of efficient high-power tunable pulse Raman lasers, operating in the near and middle ir are reviewed. The paper includes: tunable dye and Nd lasers as pump sources; promising active media and their optimal excitation methods; optical systems for producing spatially homogeneous pumping; the physics of Raman oscillators and their practical schemes, efficient high pulse energy liquid N2 and compressed H2 Raman oscillators, covering several bands in the range between 1.4 and 9.2 μm; the physics and construction of efficient tunable Raman amplifiers-convertors, amplifying in the saturation regime of spontaneously scattered or beforehand produced and collimated external Stokes signals, obtained in the spectral range between 0.83 μm and 18 μm. Raman laser using a, so-called, broadband pump where the linewidth of pumping light is broader than the spontaneous scattering linewidth, are also discussed. Features of both amplification and oscillation regimes of such broadband pumped Raman lasers are reported, and conditions for the efficient frequency conversion are determined.
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  • 55
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    Notes: Abstract Design and operating caracteristics of high pulse repetition rate NH3 laser producing up to 20 W of average output power are described. The NH3 laser, operating in the 12–13 μm region was optically pumped with a high pulse repetition rate TEA CO2 laser. Dependences of the NH3 laser output on the pump energy, ammonia and buffer gas pressures and pulse repetition rate have been studied. The conversion efficiency of up to 16% has been received.
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  • 56
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    Keywords: 35 ; 42.55 ; 42.68
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    Notes: Abstract We report the first accurate measurements of the transition strengths and linewidths of the 00o2 9.4 μm sequence lines of CO2. This sequence band is found to be very similar to the regular 00o1 laser band, except for an experimentally determined factor of 1.89±0.12 increase in transition strength (if the CO2 molecule is treated as a simple harmonic oscillator the theoretical increase in transition strength is 2.0). The laser absorption spectrometer used for these measurements can detect absorption coefficients in CO2 of ≈10−7 m−1, and we discuss the feasibility of using this sensitivity to monitor rare isotopic forms of CO2.
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  • 57
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    Applied physics 19 (1979), S. 243-245 
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    Notes: Abstract Stable step-tunable simultaneous double-wavelength emission from any branch combination of the 9.6 and 10.6 μm bands of a cw CO2 laser is reported in which the relative strengths of the two signals may be controlled.
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  • 58
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    Applied physics 18 (1979), S. 177-181 
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    Keywords: 42.55 ; 42.65 ; 33
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    Notes: Abstract We have studied experimentally stimulated Raman scattering and 4-wave-interaction processes occuring in hydrogen gas, which is excited by a Nd:YAG-pumped dye laser. The tuning ranges of the various Stokes and anti-Stokes lines, which are generated with high efficiency, cover the spectrum from 185 to 880 nm without a gap.
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  • 59
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    Applied physics 20 (1979), S. 129-134 
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    Keywords: 42.55 ; 33 ; 82.50
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    Notes: Abstract Collisional coupling between theB, C, andD states of KrF is measured in a discharge pumped KrF laser. Detection of the time resolved populations in the three states via measurement of the side fluorescence in theB→X, C→A, andD→X bands is used to record the collisional relaxation from theC andD state to theB state during laser emission. The experimentally determined limits for the collisional coupling times are τB-C≦1 ns and τB-D,τC-D〈20 ns at total pressures of 2 bar. Investigation of theB→X fluorescence band shows that the vibrational manifold of theB state is not thermalized during laser emission. TheV-V,T coupling time is estimated to be τV-V,T=4±2 ns. The influence of collisional coupling on energy extraction in the KrF laser is discussed.
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    Notes: Abstract An analytical treatment of the ultrashort-pulse generation in a solid-state laser is given taking into account gain saturation. The probability for the breakdown of the picosecond-pulse evolution caused by the amplification depletion is calculated. The influence of the active medium saturation on the satellite-pulse probability is investigated. Both probabilities characterize the mode-locking behaviour of the laser system and are calculated for various laser parameters to find an optimum laser regime.
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    Applied physics 19 (1979), S. 127-130 
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    Notes: Abstract The possibility of using stimulated emission from the recombination of electron-positron pairs for obtaining coherent γ-rays is considered. The critical number of pairs needed for the process is calculated.
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    Applied physics 19 (1979), S. 359-361 
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    Notes: Abstract This paper describes a 1 m-long CW HCN discharge laser with a hollow dielectric rectangular discharge tube of 5×20 cm2 cross-section. For optimum working conditions, the characteristics of the amplifying medium have been made constant over the cross-section, by using an additional magnetic field. Then, the unsaturated gain for the 337 μm line is 6.8% m−1. It is shown to be dependent on the smaller dimension of the cross-section rather than on the other dimension. By using the tube as a waveguide, laser output power of 1 Watt might be obtained with a discharge length of 4 m, instead of the 12m-long discharge required to get the same output power from a cylindrical waveguide laser.
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    Applied physics 20 (1979), S. 257-259 
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    Keywords: 87 ; 42.55
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    Notes: Abstract Selective electronic excitation of single kinds of DNA bases were performed with dye lasers. Different DNA-dye-complexes were used and the selective excitation could be proved by the varying strength of the interaction between the bases and the dye molecules.
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    Applied physics 20 (1979), S. 261-264 
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    Notes: Abstract The method of Stimulated Mandelshtam-Brillouin Scattering (SMBS) is utilized in a powerful laser to obtain better transverse beam quality by phase conjugation. The principle is explained, and the conclusions are substantiated by experimental results.
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  • 65
    ISSN: 1432-2048
    Keywords: Bryophyllum ; Circadian rhythm ; CO2 output ; Phytochrome ; Red light ; Rhythm (circadian)
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    Topics: Biology
    Notes: Abstract The rhythm of carbon dioxide output in Bryophyllum leaves was entrained on exposure to 0.25 h of white light every 24 h. Entrainment also occurred on similar exposure to monochromatic radiation in spectral bands centred at 660 nm and, to a lesser extent, at 730 nm, but a band centred at 450 nm was without effect. A “skeleton” irradiation programme comprising two 0.25-h exposures to white light per 24 h also entrained the rhythm when the intervening dark periods were either 7.5 h and 16 h, or 10.5 h and 13 h. The rhythm disappeared when the two exposures were separated by 11.5-h and 12-h dark periods. Regular 0.25-h exposures to red light separated by 11.75-h periods of darkness also resulted in loss of the rhythm. Red/far-red reversibility was observed in irradiation schedules having either one or two exposures to red light daily. In the latter case, far-red reversal of the effects of one of the exposures to red light resulted in entrainment of the rhythm by the other, instead of abolition of the rhythm. The occurrence of distinct red/far-red reversibility suggests strongly that phytochrome is the pigment involved in entrainment of this rhythm by cycles of light and darkness.
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  • 66
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    Planta 133 (1977), S. 169-177 
    ISSN: 1432-2048
    Keywords: Cell fractionation ; Cucurbita ; Histochemical staining ; Phosphotungstate-chromate staining ; Phytochrome ; Plasma membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The phosphotungstic acid-chromic acid (PTA-CrO3) stain, putatively specific for the plasma membrane of plants, has been used in an attempt to monitor the distribution of this membrane in a 20,000 x g particulate fraction from Cucurbita hypocotyl hooks. On discontinuous sucrose gradients, the relative distributions of the phytochrome and PTA-CrO3-positive vesicles present in this fraction appear to be correlated. When intact tissue is stained, however, other components, in addition to the plasma membrane, react positively to the stain. These components include prolamellar-body membranes, lipid droplets, and ribosomes. This lack of specificity calls into question the reliability of the technique for the unequivocal identification and accurate quantitation of plasma-membrane fragments in isolated particulate fractions. The present data do not, therefore, provide unambiguous evidence that phytochrome is associated with plasma membrane in tissue homogenates from Cucurbita.
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    Planta 134 (1977), S. 11-16 
    ISSN: 1432-2048
    Keywords: Brassica ; Chlorophyll ; Cotyledons ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phytochrome determinations at 730/800 nm were performed on de-etiolated turnip (Brassica rapa L.) cotyledons in which chlorophyll (Chl) content had been reduced experimentally to varying degrees by pre-treatment with high temperature (HT), or transfer to 3% ethanol. The magnitude of detectable phytochrome depended on Chl content, showing a linear relationshop in vivo. The results were confirmed by an in vitro experiment where, however, the correlation was exponential. An attempt is made to illustrate phytochrome decay in continuous blue or red light after corretion for Chl interference. To overcome the possible objection that the higher Δ(ΔA) measured in continuous light after HT pre-treatment could be caused by a reduced rate of destruction, apparent re-synthesis following red light was measured after several hours of darkness during which time the HT effect was lost. Under these conditions HT pre-treated samples display a more realistic magnitude of apparent new synthesis and make correlation with a physiological response possible.
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  • 68
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    Planta 134 (1977), S. 57-59 
    ISSN: 1432-2048
    Keywords: Cell culture ; Clycine ; Phytochrome
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    Notes: Abstract No phytochrome can be detected spectrophotometrically in soybean (Glycine max (L.) Merr. cv. Mandarin) cell suspensions grown in darkness. White light from a tungsten filament lamp and a band of far-red light have been found to induce the appearance of phytochrome in them. Red light failed to bring about phytochrome increase and destroyed the phytochrome induced by far-red light.
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  • 69
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    Planta 135 (1977), S. 119-123 
    ISSN: 1432-2048
    Keywords: Chlorophyll ; Phytochrome
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    Notes: Abstract Measurements of phytochrome by Δ (ΔA725–815 nm) were completely suppressed at chlorophyll concentrations of the order of 20–40 μg g-1 f.wt. in vivo and 37 μg cm-3 in vitro, and the readings were reduced by 50% at only 12 μg cm-3 in vitro. At these concentrations of chlorophyll in aqueous methanol, the loss of phytochrome signal in vitro appeared to be due to failure of phytochrome photoconversion rather than to interference with ΔA measuremebt by chlorophyll fluorescence in the 125/815 nm measuring beam.
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  • 70
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    Planta 136 (1977), S. 125-129 
    ISSN: 1432-2048
    Keywords: Blue-light-response ; Elongation ; High-irradiance-response ; Photomorphogenesis ; Phytochrome ; Raphanus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In etiolated hypocotyls of Raphanus sativus L. the growth responses to continuous red, far-red and blue light have been distinguished on the bases of photoreceptive sites and regions of physiological response. Blue light appeared to retard a fairly mature stage of elongation, acting immediately and directly on the cells irradiated. Far-red light caused a marked inhibition of all stages of elongation after a lag period, and the stimulus could be transmitted from the hook region. The effect of red light was complex and consisted of one promotive and two inhibitory responses.
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  • 71
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    Planta 136 (1977), S. 131-134 
    ISSN: 1432-2048
    Keywords: Action-spectrum ; Blue-light photoreceptor ; High-irradiance-response ; Photomor-phogenesis ; Phytochrome ; Raphanus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In etiolated seedlings of Raphanus sativus L. the inhibition of hypocotyl elongation by continuous light showed a major bimodal peak of action in the red and far-red, and two minor peaks in the blue regions of the spectrum. It is argued that, under conditions of prolonged irradiation, phytochrome is the pigment controlling the inhibition of hypocotyl elongation by red and far-red light, but that its mode of action in far-red is different from that in red. A distinct pigment is postulated for blue light.
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  • 72
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    Planta 136 (1977), S. 181-186 
    ISSN: 1432-2048
    Keywords: Enzyme Regulation ; Sinapis alba ; Phytochrome ; Phenylalanine ammonia-lyase ; Ribulosebisphosphate carboxylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phytochrome controls the appearance of many enzymes in the mustard (Sinapis alba L.) cotyledons. The problem has been whether the effect of phytochrome on the appearance of enzymes in this organ is due to a common initial action of Pfr, e.g. due to the liberation of a “second messenger”. We have compared the modulation by light (phytochrome) of the appearance of phenylalanine ammonia lyase (PAL)+ and ribulosebisphosphate carboxylase (Carboxylase)+. PAL becomes detectable in the mustard cotyledons at 27 h after sowing while Carboxylase starts to appear only at 42 h after sowing (starting points, 25° C). The starting points cannot be shifted by light. As a major result, in the case of PAL the inductive effect of continuous red light (given from the time of sowing) remains fully reversible by 756 nm-light up to the starting point (27 h after sowing) while with Carboxylase full reversibility in continuous red light is lost at approximately 15 h after sowing. While the induction of Carboxylase is already saturated at a very low level of Pfr (e.g. continuous 756 nm-light saturates the response) and does not depend on irradiance (e.g. continuous 675 mW m-2 red light and 67.5 mW m-2 red light lead to the same time course), PAL induction is a graded response over a wide range of Pfr doses and depends strongly on the fluence rate (high irradiance response, HIR). It is concluded that PAL induction and Carboxylase induction are not only separated in time but differ in every regard except that both responses are mediated by phytochrome. The present data support the previous conclusion that the specification of the temporal and spatial pattern of development is independent of phytochrome even though the realization of the pattern of development can only occur in the presence of phytochrome (Pfr). It seems that there is no feedback from pattern realization to pattern specification.
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  • 73
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    Planta 137 (1977), S. 61-64 
    ISSN: 1432-2048
    Keywords: Phaseolus ; Phytochrome ; Potassium uptake
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    Notes: Abstract Uptake of potassium (K) and 86rubidiumlabelled potassium (86Rb) by sub-hypocotyl hook sections of Phaseolus aureus L. was inhibited by red light. The effect was reversible with far red light. Using short exposures of high irradiance the effect on 86Rb-labelled K uptake was observed after 5 min. The response showed no specificity for a particular anion. Uptake of 86Rb-labelled K by sections cut immediately below the cotyledons was enhanced by red light after 10 min incubation and was also far red reversible. These results are interpreted as a rapid phytochrome-induced change in membrane properties resulting in modified K uptake.
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  • 74
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    Planta 137 (1977), S. 225-229 
    ISSN: 1432-2048
    Keywords: Calcium Ions ; Membrane potential ; Nitella ; Phytochrome
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    Topics: Biology
    Notes: Abstract Isolated internodes of Nitella (N. opaca, N. flexilis) and Nitellopsis spec. were punctured with single microelectrodes and their membrane potentials were recorded continuously during various light treatments. In red light the initial response was always a depolarization. This depolarization began with a lag-time of 0.4-3.5s and reached a steady state within 1–2 min of continuous illumination. Repolarization began within several seconds after turning off the light. The magnitude of the red-light-induced depolarization increased with the Ca2+-concentration of the medium. The largest depolarizations were recorded in 5 m mol l-1 Ca2+. Ca2+ could not be replaced in this function by Na+, Mg2+, La3+ or mannitol. Far-red light alone had no effect on the resting membrane potential. Far-red light applied immediately after red light accelerated the repolarization of the membrane potential. Far-red light applied simultaneously with red light reduced the amount of depolarization and increased the rate of repolarization. The results indicate that phytochrome and Ca2+ are involved in the light-induced depolarization of the membrane. They are consistent with the hypothesis that phytochrome may act by triggering a Ca2+-influx at the plasma membrane.
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  • 75
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    Planta 138 (1978), S. 25-28 
    ISSN: 1432-2048
    Keywords: Action spectrum ; Chlorophyll ; Phaseolus ; Photomorphogenesis ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Red light absorption by photosynthetic pigments screens stem tissue of Phaseolus vulgaris L. seedlings to such an extent that the most effective wavelength for the phytochrome induction control of stem growth is approximately 628 nm. Screening is greater in the first internode than in the hypocotyl. The consequences are that, compared with etiolated seedlings, much higher irradiances are required for phytochrome control in green plants, and the efficiency of 660 nm light is markedly reduced. Even very high exposures at 660 nm may not achieve appreciable photoconversion of P r to P fr.
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  • 76
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    Keywords: Adiantum ; Blue-light effect ; Cell division ; Light, microbeam ; Photomorphogenesis ; Phytochrome
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    Notes: Abstract Protonemata of the fern Adiantum capillusveneris L., grown as single-cell filaments under continuous red light, were irradiated with a narrow beam of blue light. Only irradiation of the region containing the nucleus induced cell division. Beams of 30 μm in width, which corresponds to the diameter of the nucleus, or wider, were equally effective; beams 10 μm wide or less were less effective. The results indicate that the nuclear region is the site of the blue- and near ultraviolet-light-absorbing pigment (PB-NUV) which mediates the timing effect of cell division. In contrast, the effect of a narrow beam of far-red (FR) light, which delays the onset of the blue-light-induced cell division, was found to be present along the entire length of the protonema cell, including the largely vacuolated basal region of the latter. Polarized FR light having the electrical vector parallel to the protonema axis was less effective than that vibrating in other directions. These observations support the hypothesis that the phytochrome controlling the timing effect is localized in the plasma membrane.
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  • 77
    ISSN: 1432-2048
    Keywords: Lemna ; Membrane potential ; Phytochrome
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    Topics: Biology
    Notes: Abstract Light-stimulated transmembrane potential changes have been measured continuously after implantation of microelectrodes into subepidermal cells of the short-day plant Lemna paucicostata 6746. Irradiation for 5 min with white or red light caused a transient hyperpolarization. These potential changes could be suppressed with 10-6 M DCMU. Irradiation of DCMU-inhibited plants with far-red light for 5 min hyperpolarized the membrane potential, which thereafter was not changed by further far-red application. Consecutive red light irradiation for 5 min depolarized the membrane potential. The red/far-red reversibility of the potential changes (which could be repeated several times with a single plant) suggests the participation of phytochrome.
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  • 78
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    Planta 141 (1978), S. 1-7 
    ISSN: 1432-2048
    Keywords: Flowering ; Pharbitis ; Photomorphogenesis ; Photoperiodic induction ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract For dark-grown seedlings of Pharbitis nil capacity to flower in response to a single inductive dark period was established by 24 h white, far-red (FR) or ruby-red (BCJ) light and by a skeleton photoperiod of 10 min red (R)-24 h dark-10 min R. FR alone was ineffective without a brief terminal (R) irradiation, confirming that the form of phytochrome immediately prior to darkness is a crucial factor for flowering in Pharbitis. The magnitude of the flowering response was significantly greater after 24 h FR or white light (WL) (at 18° C and 27° C) than after two brief skeleton R irradiations, but the increased flowering response was not attributable to photosynthetic CO2 uptake because this could not be detected in seedlings exposed to 24 h WL at 18° C. Photophosphorylation could have contributed to the increased flowering response as photosystem I fluorescence was detectable in plants exposed to FR, BCJ, or WL, but there were large differences between flowering response and photosystem I capacity as indicated by fluorescence. We conclude that phytochrome plays a major role in photoresponses regulating flowering. There was no simple correlation between developmental changes, such as cotyledon expansion and chlorophyll formation during the 24-h irradiation period, and the capacity to flower in response to a following inductive dark period. Changes in plastid ultrastructure were considerable in light from fluorescent lamps and there was complete breakdown of the prolamellar body with or without lamellar stacking at 27 or 18° C, respectively, but plastid reorganization was minimal in FR-irradiated seedlings.
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  • 79
    ISSN: 1432-2048
    Keywords: Hordeum ; Membranes ; Organelles ; Phytochrome
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    Topics: Biology
    Notes: Abstract Red light treatment in vitro increases the pelletability of phytochrome in homogenates of etiolated barley (Hordeum vulgare L. cv. ‘Julia’) leaves. When mixtures of soluble phytochrome (100,000 x g supernatant) and partially-purified organelles (Sephadex G-50 eluate) are irradiated the amount of pelletable phytochrome increases by a factor of two. Pre-irradiation treatments show that phytochrome in both components of the mixture must be in the Pfr form for increased pelletability to be observed. Once associated, photoreversion of Pfr to Pr does not result in decreased pelletability. The results are consistent with a non-artifactual in vitro association of soluble phytochrome to organelle membranes. One possible explanation is that Pfr molecules associate to form dimers.
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  • 80
    ISSN: 1432-2048
    Keywords: Avena ; Immunocytochemistry ; Phytochrome
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    Topics: Biology
    Notes: Abstract Phytochrome of oat (Avena sativa L., cv. Garry) coleoptile cells in the red-light-absorbing form, Pr, is diffusely distributed while after conversion to the far-red-light-absorbing form, Pfr, it is observed only in very small areas within the cell. Comparison of phytochrome photoversibility measurements to the distribution of the pigment within the cell indicates that the spectral assay is not influenced by the observed compartmentalization of the chromoprotein. However, the observed compartmentalization of phytochrome is correlated with a loss in spectrophotometrically detectable Pr.
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  • 81
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    Planta 141 (1978), S. 211-216 
    ISSN: 1432-2048
    Keywords: Hypocotyl growth ; Photomorphogenesis ; Phytochrome ; Sinapis
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    Topics: Biology
    Notes: Abstract After sowing, mustard (Sinapis alba L.) seedlings were grown for 48 h in white light (25°C). These fully de-etiolated, green seedlings were used as experimental material between 48 and 72 (84) h after sowing. The question researched was to what extent control by light of hypocotyl elongation is due to phytochrome in these seedlings. It was found that the light effect on hypocotyl growth is very probably exerted through phytochrome only. In particular, we found no indication for the involvement of a specific blue light photoreceptor pigment.
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  • 82
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    Keywords: Avena ; Etioplasts ; Mitochondria ; Phytochrome
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    Notes: Abstract Phytochrome was determined in etiolated laminae of Avena sativaL. either without pretreatment or after 5 min of red irradiation followed by different periods of darkness (0–24 h). At given intervals laminae were homogenized and phytochrome was determined spectrophotometrically in the total homogenate and in purified etioplasts and mitochondria. Enhanced specific activity of phytochrome was found in all fractions after the irradiation in comparison to dark controls. Phytochrome destruction was observed in all fractions at the beginning of the subsequent dark period. Whereas the homogenate and the mitochondrial fraction showed a continuous destruction so that phytochrome reached a level far below that in etiolated plants, the phytochrome level in the plastid fraction reacheda minimum at 2 h with a subsequent increase beyond the dark level. This increase was most pronounced between 4 and 8 h after the red irradiation. The results are discussed in terms of the destruction and possible de novo synthesis of phytochrome that may be different in mitochondria and plastids.
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  • 83
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    Planta 144 (1978), S. 1-5 
    ISSN: 1432-2048
    Keywords: Germination (seeds) ; Lactuca ; Phytochrome ; Seed germination
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    Topics: Biology
    Notes: Abstract Germination of certain dry “seeds” (achenes) of Lactuca sativa L. cv. Grand Rapids was increased to ca. 75% after irradiation with 665 nm red light (R; 1x103 J m-2); this response was eliminated by far-red light (FR) following the R. The response of dry seeds required an order of magnitude more light than that of wetted seeds, and was not maximal until 48 h after irradiation. Other seeds, which could not be stimulated by R in dry state, showed a partial response after 10 min hydration. Irradiation of dry seeds (or seeds wetted 1 h) with FR (1x103 J m-2) reduced dark germination from 26% to 2%. Seeds dehydrated in an oven (60°C, 90 min) showed a decrease in germination if irradiated with R (1x105 J m-2) before wetting. The results show that phytochrome is present in dry lettuce seeds (and functional in some seed lots) prior to wetting; and that in other seed lots the molecule becomes functional within minutes after wetting the seeds. Transformation of the FR absorbing from of phytochrome (PFR) to the inactive from (PR) occurs at lower seed moisture content than the reverse reaction. It appears that dormancy in seeds ripened in sunlight might be assured during seed drying and maturation by the more effective transformation of PFR to PR than vice versa as phytochrome is dehydrated.
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  • 84
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    Planta 143 (1978), S. 309-313 
    ISSN: 1432-2048
    Keywords: Avena ; Light-grown tissue ; Phytochrome ; San 9789
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phytochrome was studied spectrophotometrically in Avena sativa L. seedlings that had been grown for 6 d in continous white fluorescent light from lamps. Greening was prevented through the use of the herbicide San 9789. When placed in the light, phytochrome (Ptot) decreased with first order kinetics (τ1/2 ≈ 2 h) but reached a stable low level (≈2.5% of the dark level) after 36 h. This concentration of phytochrome remained constant in the light and during the initial hours of a subsequent dark period, but increased significantly after a prolonged dark period. Evidence suggests that the constant pool of phytochrome in the light is achieved through an equilibrium between synthesis of the red absorbing (Pr) and destruction of the far-red absorbing form (Pfr) of phytochrome. It is concluded that the phytochrome system in light-grown oat seedlings is qualitatively the same as that known from etiolated monocotyledonous seedlings, but different than that described for cauliflower florets.
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  • 85
    ISSN: 1432-2048
    Keywords: Citrate synthase ; Fat degradation ; Isocitrate lyase ; Malate synthase ; Phytochrome ; Sinapis ; Starch (transitory)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The degradation of storage fat in the cotyledons of mustard seedlings is unaffected by phytochrome and photosynthesis (irradiation with continuous red or far-red light from sowing of the seeds) although light imposes a strong constraint on the translocation of organic matter from the cotyledons into the seedling axis. Likewise, the development and disappearance of glyoxysomal enzyme activities (isocitrate lyase, malate synthase, citrate synthase) takes place independently of light. It is concluded that the mobilization of storage fat (fat→carbohydrate transformation) is independent of photomorphogenesis. The surplus of carbohydrate produced from fat in the light seems to be converted to starch grains in the plastids, which function as a secondary storage pool in the cotyledons.
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  • 86
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    Planta 146 (1979), S. 31-39 
    ISSN: 1432-2048
    Keywords: Autoradiography ; Calcium ; Mougeotia ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ca2+ is proposed to function as a messenger in such phytochrome-mediated responses as localized cell growth, intracellular movements, and control of plasma membrane properties. To test this hypothesis, the uptake of Ca2+ in irradiated and non-irradiated regions of individual threads of the green alga Mougeotia was studied with the aid of 45Ca2+ and low temperature autoradiography: 10–20 cells within 40–60 cell-long threads were irradiated for up to 1 min, transferred to darkness for 3 to 10 min, submersed in a radioactive medium for 1 min, washed in an unlabelled medium for 30 min, and then autoradiographed at-80° C for several days. The autoradiographs show that those cells which had been pre-irradiated with red light did take up 2–10 times more Ca2+ than the adjacent non-irradiated cells of the same thread. Cells pre-irradiated with farred light or red light followed by far-red light showed no enhanced uptake of Ca2+. These results might be interpreted to indicate, firstly, that phytochrome-Pfr is involved in the enhanced uptake of Ca2+ and secondly, that the accumulation of radioactive Ca2+ in red light irradiated cells is an expression of an increased intracellular concentration of Ca2+. This interpretation is based on the data that (i) the dark interval between irradiation and labelling precluded the involvement of photosynthesis, (ii) the effect of red light was reversible with far-red light, and (iii) the accumulation of Ca2+ persisted during the long wash-out period. We speculate, that the red light-enhanced accumulation of Ca2+ in Mougeotia cells is caused by a Pfr-mediated increase of the Ca-permeability of the plasma membrane, and perhaps by a Pfr-impeding of an active Ca2+-extrusion.
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  • 87
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    Planta 143 (1978), S. 323-328 
    ISSN: 1432-2048
    Keywords: Bryophyllum ; Circadian rhythm ; Photocontrol ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A 4-h exposure to white light from fluorescent lamps can shift the phase of the rhythm of CO2 output in leaves of Bryophyllum fedtschenkoi Hamet & Perr. otherwise kept in continuous darkness. The position in the cycle at which irradiation occurs determines the magnitude and direction of the phase shift. Red and white light induce similar advances or delays in the phase, but blue and far-red irradiation have no effect. Far-red irradiation given simultaneously with, or immediately after, exposure to red light, modifies the phase-shift induced by red light alone. Radiation in the red and far-red regions of the spectrum interacted in several experimental régimes, but complete red/far-red reversibility was not observed. The evidence suggests that phytochrome is the receptor molecule involved in the induction of phase-shifts by light.
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  • 88
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    Planta 147 (1979), S. 229-235 
    ISSN: 1432-2048
    Keywords: Avena ; Greening ; Mitochondria ; Oxidative Phosphorylation ; Phytochrome ; Respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mitochondria isolated from 7-day old darkgrown Avena sativa L. (var. Arnold) laminae given 5 min illumination of red light, followed by varying lengths of darkness up to 3 h, showed at least a twofold increase in the rates of both NADH-dependent oxygen consumption and respiratory chain phosphorylation over those of mitochondria isolated from unilluminated tissue. Similar organelles, isolated from tissue given either far-red or red followed by far-red pretreatment, exhibited rates of both functions of between 25% and 75% below those of the mitochondria from unilluminated tissue. The induction-reversion criteria for phytochrome control of respiration and oxidative phosphorylation were satisfied under all experimental conditions during the greening process. Treatment with continuous far-red light, acting presumably through the ‘high irradiance’ reaction of phytochrome, served to disengage phytochrome activity from photosynthesis. The stimulation of oxidative phosphorylation still occurred under these conditions, slightly slower but much more prolonged in the absence of ATP from photophosphorylation.
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  • 89
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    Planta 143 (1978), S. 233-239 
    ISSN: 1432-2048
    Keywords: Adaptation (chromatic) ; Chromatic adaptation ; Cyanophyta (cyanobacteria) ; Phycobiliproteins ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Action spectra for chromatic adaptation in Fremyella diplosiphon Drouet have been determined using techniques previously described. Action maxima are at 540 nm, with a half-band width of 80 nm, for induction of phycoerythrin synthesis (green action) and at 650 nm, with a half-band width of 90 nm, for reversal of induction of phycoerythrin synthesis (red action). The red-action spectrum includes a secondary action band centered at ca. 360 nm. Red and green action overlap from 570 to 590 nm with an isosbestic point in the vicinity of 580 nm. Shoulders are present at 520 and 630 nm. Red light is more active than green light. The 540:650-nm quantum effectiveness ratio is 1:7. There is relatively little action of either kind in the blue. The 387:540 nm and 460:650-nm quantum effectiveness ratios are zero. These results contrast strongly with previous determinations in the same organism, with major activity indicated in the blue; they are consistent with the control of photomorphogenesis in the Cyanophyta by a master pigment, analogous to phytochrome.
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  • 90
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    Planta 137 (1977), S. 203-206 
    ISSN: 1432-2048
    Keywords: ATPase ; Membrane ; Phaseolus ; Photomorphogenesis ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Membrane-bound phytochrome and ATPase (ATP phosphohydrolase EC 3.6.1.3.) activity extracted from hypocotyl hooks of etiolated Phaseolus aureus Roxb. were both separated from solute proteins by gel filtration on Sepharose C1-2B. The amount of phytochrome detected in the membrane fraction was very small and was not significantly increased by red irradiation (in vivo or in vitro). Membrane-bound ATPase activity was modulated in vitro by the phytochrome in the membrane fraction, being lower after red light than after far-red light. This effect was potentiated by a preliminary light reaction which occurred only in vivo and, in continuous red light, required 60 to 90 s at 25°C. Thus a two minute, in vivo, red irradiation reduced membrane-bound ATPase activity to about half that of the etiolated state. Subsequently bound-ATPase activity was determined by the form of phytochrome (Pr or Pfr) irrespective of whether established in vivo or in vitro. These results indicate that binding or release (of enzyme, cofactors or inhibitors) is not involved in phytochrome modulation of enzyme activity in the membrane fraction.
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  • 91
    ISSN: 1432-2048
    Keywords: Flowering ; Pharbitis ; Photoperiodic induction ; Phytochrome ; Spectrophotometry (phytochrome)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The low chlorophyll content of cotyledons of Pharbitis nil grown for 24 h in far-red light (FR) or at 18° C in white light from fluorescent lamps (WL) allows spectrophotometric measurement of phytochrome in these tissues. The Δ(ΔA) measurements utilize measuring beams at 730/802 nm and an actinic irradiation in excess of 90 s. The constancy of the relationship between phytochrome content and sample thickness confirms that, under these conditions of measurement, a true maximum phytochrome signal was obtained. These techniques have been used to follow changes in the form and amount of phytochrome during an inductive dark period for flowering. Following exposure to 24h WL at 18° C with a terminal 10 min red (R), Pfr was lost rapidly in darkness and approached zero in less than 1 h; during this period there was no change in the total phytochrome signal. Following exposure to 24 h FR with a terminal 10 min R, Pfr approached zero in 3 h, and the total phytochrome signal decreased by about half. The relevance of these changes to photoperiodic time measurement is discussed.
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  • 92
    ISSN: 1432-2048
    Keywords: Flowering ; Pharbitis ; Photoperiodic induction ; Phytochrome ; Spectrophotometry (phytochrome)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During an inductive dark period for flowering, changes in phytochrome have been followed in cotyledons of Pharbitis nil seedlings using a spectrophotometric and a physiological technique. There was agreement between the two techniques, both indicating a rapid lowering of the levels of the far-red-absorbing form of the pigment (Pfr) during the first 30–90 min of darkness. Thus, Pfr could provide the cue which signals the beginning of darkness and the length of the critical dark period was, in some instances, correlated with the time of Pfr disappearance. However, there was no correlation with another indicator of photoperiodic time measurement, the time in darkness at which a brief night interruption becomes inhibitory to flowering. These results imply that the transition from light to darkness is not signalled by the disappearance of Pfr. However, the involvement of other photoreceptors seems unlikely. Thus, some mode of phytochrome action other than a simple Pfr-mediated response may be involved in the light/dark-sensing reactions of photoperiodism
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  • 93
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    Planta 145 (1979), S. 405-409 
    ISSN: 1432-2048
    Keywords: Chenopodium ; Internode elongation ; Photoreception sites ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The elongation of the fourth internode of ‘fully green’ Chenopodium polyspermum L. is modulated by far-red light (FR) given in addition to the main light period. Two different types of organs are responsible for the photoreception of FR producing the end-of-day effect; the stem and the leaves situated just above and below the reacting internode. Photoreversibility can be obtained within certain limits in the two organs. Evidence is presented which shows that in the ‘fully green’ plant there is an interorgan reaction whose primary reaction is the photoconversion of phytochrome.
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  • 94
    ISSN: 1432-2048
    Keywords: Carotenoids ; Chlorophylls ; Herbicides ; Phytochrome ; Plastid development ; Ribulosebisphosphate carboxylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Treatment of the mustard (Sinapis alba L.) seedling with the herbicide SAN 9789 inhibits synthesis of colored carotenoids and interferes with the formation of plastid membrane lipids without affecting growth and morphogenesis significantly. In farred light, which is hardly absorbed by chlorophyll, development of plastid ultrastructure, synthesis of ribulosebisphosphate carboxylase and synthesis of chlorophyll are not affected by SAN 9789. It is concluded that normal phytochrome actions on plastid structural development, protein and chlorophyll syntheses are not affected by the absence of carotenoids provided that there is no significant light absorption in chlorophyll. The findings show that the inhibition of synthesis of one set of plastid membrane components (the carotenoids) does not stop synthesis of other components such as chlorophyll and does not halt membrane assembly. Supplementary experiments with the closely related compound SAN 9785, which affects the amount and composition of plastid lipids but not carotenoid and chlorophyll syntheses, suggest that the effect of the herbicide SAN 9789 is due exclusively to its inhibition of synthesis of colored carotenoids. In the presence of SAN 9789 white or red light at high fluence rate causes photodestruction of chlorophyll and ribulosebisphosphate carboxylase and photodecomposition of thylakoids. These effects are interpreted as resulting exclusively from the self-photooxidation and photosensitizing action of chlorophyll once the protection by carotenoids of chlorophyll against self- and sensitized photooxidation is lost.
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  • 95
    ISSN: 1432-2048
    Keywords: Chlorophyll ; Chloroplasts ; Grana ; Phytochrome ; Sinapis ; Thylakoids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The etioplast»chloroplast transition in the cotyledons of mustard seedlings (Sinapis alba L.) has been studied by electron microscopy. It was found that the active form of phytochrome, established by a red light pulse pretreatment, increases the initial rate and eliminates the lag of grana and stroma thylakoid formation after the onset of white light 60 h after sowing. The effect of a pretreatment with 15 s red light pulses is fully reversible by 756 nm light pulses. This reversibility is lost within 5 min. Evidence is presented which suggests that the time course of grana and stroma thylakoid formation is not correlated with the time course of the dispersal of the prolamellar body. The different functions of phytochrome and chlorophyll in controlling thylakoid formation are discussed.
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  • 96
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    Planta 142 (1978), S. 119-122 
    ISSN: 1432-2048
    Keywords: Chlorophyll ; Ethylene ; Phenylalanine ammonia-lyase ; Phytochrome ; Sinapis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The concept (Burg, 1973) that ethylene mediates the action of phytochrome in seedling photomorphogenesis was tested in the intact mustard (Sinapis alba L.) seedling. The effect of exogenous ethylene (100 μl l−1) on five distinct, phytochrome-mediated photoresponses of the cotyledons was investigated. It was found that anthocyanin contents (see Bühler et al., 1978) and phenylalanine ammonia-lyase levels (EC 4.3.1.5) are strongly reduced by ethylene while the capacity of chlorophyll synthesis is considerably enhanced. Levels of glutathione reductase (EC 1.6.4.2) and pools of photoconvertible protochlorophyll(ide) are unaffected by ethylene. It is concluded that these findings are incompatible with the idea that ethylene plays the role of a mediator in phytochrome-induced photomorphogenesis.
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  • 97
    ISSN: 1432-2048
    Keywords: Chenopodium ; Far-red ; Photoequilibrium ; Phytochrome ; Stem extension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chenopodium album seedlings were grown in light environments in which supplementary far-red light was mixed with white fluorescent light during various parts of the photoperiod. Both the logarithmic rate constant of stem extension and the leaf dry weight: stem dry weight ratio were linearly related to estimated phytochrome photoequilibrium (ϕ) in each treatment regime. These data are taken to be indicative of a functional link between phytochrome and development in the green plant. A layer of chlorophyllous tissue only affected the linearity between calculated ϕ and the logarithmic stem extension rate at high chlorophyll concentrations, whilst even low concentrations-equivalent to the levels found in stem tissue-caused a significant shift in measured ϕ. End-of-day supplementary far-red (FR) light induced between 0–35 per cent of the response elicited by all-day supplementary FR, whilst daytime supplementary FR (with a white fluorescent light end-of-day treatment) induced approximately 90 per cent. The ecological significance of this difference is discussed with respect to shade detection.
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  • 98
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    Planta 143 (1978), S. 109-111 
    ISSN: 1432-2048
    Keywords: Boron ; Fluorescein ; Gravity ; Phytochrome ; Vigna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Hypocotyl sections from dark-grown mung bean (Vigna radiata (L.) Wilczek) seedlings grown without boron exhibit little or no increase in the translocation of fluorescein in phloem cells following gravitational stimulation or red irradiation. In contrast, pretreatment of the hypocotyl sections with low concentrations of boric acid before red irradiation or gravitational stimulation results in a rapid increase in fluorescein movement. Mung bean root tips without boron fail to remain attached to a negativelycharged glass surface after several minutes of red irradiation. A low boron concentration in the solution induces tip attachment. The suggestion is made that boron is required to stabilize a positive electrostatic charge in the plasma membrane that is generated by the actions of phytochrome and gravity.
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  • 99
    ISSN: 1432-2048
    Keywords: Phytochrome ; Development habitat ; Natural radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A survey of the responsiveness of plant species, typical of open and shade habitats, to simulated natural shade-light quality (i.e. white light plus supplementary far-red) has demonstrated a systematic relationship between habitat and certain developmental responses. Supplementary far-red light has a much greater effect on stem extension rate, petiole length, and leaf dry weight: stem dry weight ratio of the open habitat, shade-intolerant species. Far-red effects on leaf chlorophyll content show no such systematic grading. These results are discussed in relation to habitat adaptation. In most cases, the relationship between developmental response and the estimated phytochrome photoequilibrium, which is established by the radiation treatment, is linear. This is taken as an indication of phytochrome involvement in shade perception.
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  • 100
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    Planta 145 (1979), S. 269-272 
    ISSN: 1432-2048
    Keywords: Flowering ; Gibberellin ; Photoperiodism ; Phytochrome ; Sorghum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Combinations of far-red light (FR) (4 min) and gibberellic acid (GA3), given at the beginning of a daily 12-h dark period in a growth room, were used to study floral induction in four maturity genotypes of the milo group of sorghum (Sorghum bicolor (L.) Moench). The 12-h dark period without GA3 application or FR induced flowering in only the early genotype; FR hastened initiation in the early genotype, while GA3 hastened floral initiation in the two intermidiate-flowering genotypes. GA3 and FR together had a strong synergistic effect, hastening floral initiation by 30 to more than 80 d in the early and intermediate genotypes. Red light (R) did not hasten flowering; FR preceded by R gave the same effect as FR alone. GA3 promoted stem elongation equally whether floral initiation occurred or not; thus, its effect on stem elongation was independent of floral initiation. The capacity of GA3 to induce flowering in sorghum, a short-day plant, seems to be enhanced by phytochrome being in the PR form at the beginning of the night when GA3 was applied.
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