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  • 42.55  (64)
  • 01. Atmosphere::01.01. Atmosphere::01.01.07. Volcanic effects
  • kinetics
  • Springer  (97)
  • American Geophysical Union
  • Copernicus
  • 1975-1979  (97)
Sammlung
Verlag/Herausgeber
  • Springer  (97)
  • American Geophysical Union
  • Copernicus
Erscheinungszeitraum
Jahr
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Journal of solution chemistry 6 (1977), S. 203-216 
    ISSN: 1572-8927
    Schlagwort(e): Glucose ; kinetics ; mixed solvent ; kinetic isotope effect ; enthalpy of activation ; entropy of activation ; tetrahydrofuran ; tert-butanol ; mutarotation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The mutarotation rates of glucose in aqueous mixtures of tetrahydrofuran andtert-butanol in the mole fraction (xi) range 0〈xi〈0.2 have been measured at 5° intervals in the range 5–35°C. The kinetic deuterium isotope effects have been determined for the same solvent compositions at 25 and 35°C. A statistical analysis of the Arrhenius plots indicates that the experimental errors, although small, are too large for the establishment of any compensation behavior between ΔH
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of solution chemistry 5 (1976), S. 163-169 
    ISSN: 1572-8927
    Schlagwort(e): Solvent effects ; tetramethylurea ; hydrolysis ; hydrogen bonding ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Tetramethylurea was hydrolyzed in aqueous hydrochloric acid at temperatures of 80, 90, and 100°C. All reactions were carried out in an excess of both tetramethylurea and water, with first-order dependence on acid concentration being observed. As the concentration of water was increased, the rate of hydrolysis decreased until equimolar amounts of water and tetramethylurea were present. Subsequent addition of water had no effect on the observed rate.
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  • 3
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 14 (1977), S. 277-282 
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 52
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 18 (1979), S. 333-338 
    ISSN: 1432-0630
    Schlagwort(e): 87 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 19 (1979), S. 47-51 
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 42.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 19 (1979), S. 345-351 
    ISSN: 1432-0630
    Schlagwort(e): 78.55 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 13 (1977), S. 97-99 
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 82.50
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 13 (1977), S. 383-385 
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 42.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 14 (1977), S. 25-28 
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 42.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 14 (1977), S. 393-398 
    ISSN: 1432-0630
    Schlagwort(e): 34 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 14 (1977), S. 193-197 
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 52
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 14 (1977), S. 255-268 
    ISSN: 1432-0630
    Schlagwort(e): 42.80 ; 42.55 ; 85.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 15 (1978), S. 185-190 
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 15
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 15 (1978), S. 229-232 
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 15 (1978), S. 439-450 
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 16 (1978), S. 297-301 
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 16 (1978), S. 151-154 
    ISSN: 1432-0630
    Schlagwort(e): 42.65 ; 42.55 ; 33
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 13 (1977), S. 109-110 
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 17 (1978), S. 367-370 
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 78.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 14 (1977), S. 121-122 
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 18 (1979), S. 257-260 
    ISSN: 1432-0630
    Schlagwort(e): 32 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 23
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 15 (1978), S. 191-196 
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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 %.
    Materialart: Digitale Medien
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  • 24
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 17 (1978), S. 181-187 
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 19 (1979), S. 205-212 
    ISSN: 1432-0630
    Schlagwort(e): 33 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 26
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 19 (1979), S. 241-242 
    ISSN: 1432-0630
    Schlagwort(e): 33 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 27
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 19 (1979), S. 399-403 
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 28
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 19 (1979), S. 427-429 
    ISSN: 1432-0630
    Schlagwort(e): 33 ; 35 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 29
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 19 (1979), S. 439-440 
    ISSN: 1432-0630
    Schlagwort(e): 07 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 30
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 18 (1979), S. 235-241 
    ISSN: 1432-0630
    Schlagwort(e): 42.65C ; 42.55 ; 33.20
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 31
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 20 (1979), S. 41-50 
    ISSN: 1432-0630
    Schlagwort(e): 41 ; 42.55 ; 95
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 32
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 20 (1979), S. 61-65 
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 33
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 20 (1979), S. 97-99 
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 34
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 13 (1977), S. 107-108 
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 35
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 17 (1978), S. 257-267 
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 32.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 36
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 15 (1978), S. 59-63 
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 37
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 19 (1979), S. 39-41 
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 38
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 18 (1979), S. 415-419 
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 39
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 19 (1979), S. 35-37 
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 40
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 19 (1979), S. 185-189 
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 41
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 18 (1979), S. 77-80 
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 78.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 42
    ISSN: 1432-0630
    Schlagwort(e): 32 ; 34 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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).
    Materialart: Digitale Medien
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  • 43
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 19 (1979), S. 165-170 
    ISSN: 1432-0630
    Schlagwort(e): 33 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 44
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 19 (1979), S. 221-224 
    ISSN: 1432-0630
    Schlagwort(e): 42.10 ; 42.55 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 45
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 19 (1979), S. 257-264 
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 46
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 13 (1977), S. 1-3 
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 47
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 13 (1977), S. 55-58 
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 78.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 48
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 14 (1977), S. 343-350 
    ISSN: 1432-0630
    Schlagwort(e): 33 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 49
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 14 (1977), S. 377-380 
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 50
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 15 (1978), S. 265-270 
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 51
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 16 (1978), S. 155-158 
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 78.60 ; 85.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 52
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 53
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 14 (1977), S. 199-203 
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 82.50
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 54
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 17 (1978), S. 303-307 
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 55
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 17 (1978), S. 393-400 
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 56
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 17 (1978), S. 211-232 
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 42.65 ; 42.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 57
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 58
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 17 (1978), S. 349-353 
    ISSN: 1432-0630
    Schlagwort(e): 35 ; 42.55 ; 42.68
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 59
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 19 (1979), S. 243-245 
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 60
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 18 (1979), S. 177-181 
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 42.65 ; 33
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 61
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 20 (1979), S. 129-134 
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 33 ; 82.50
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 62
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 63
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 19 (1979), S. 127-130 
    ISSN: 1432-0630
    Schlagwort(e): 42.55 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 64
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 19 (1979), S. 359-361 
    ISSN: 1432-0630
    Schlagwort(e): 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 65
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 20 (1979), S. 257-259 
    ISSN: 1432-0630
    Schlagwort(e): 87 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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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  • 66
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 20 (1979), S. 261-264 
    ISSN: 1432-0630
    Schlagwort(e): 42.65 ; 42.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 67
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 10 (1976), S. 43-48 
    ISSN: 1432-1041
    Schlagwort(e): Spironolactone ; acetylsalicylic acid ; fludrocortisone ; kinetics ; pharmacology ; interaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The influence of 600 mg acetylsalicylic acid (ASA) on the renal excretion and clearance of canrenone, the principal unconjugated metabolite of spironolactone, was examined in a double-blind crossover study in six healthy subjects. ASA significantly reduced the urinary excretion, and the fractional excretion, of canrenone between 4 — 6 hours after administration of 50 mg spironolactone. The pharmacological activity of spironolactone, assessed simultaneously by alterations in fludrocortisone-induced urinary electrolyte changes, was slightly but not significantly reduced. The reductions in urinary canrenone excretion correlated with changes in the urinary log 10 Na/K ratio. The results suggest that canrenone may be actively secreted at the proximal renal tubule, and that secretion is blocked by ASA or its conjugates. This is a possible mechanism for the pharmacological interaction between ASA and spironolactone which has been described previously.
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  • 68
    ISSN: 1432-1041
    Schlagwort(e): Theophylline ; kinetics ; apnea ; premature newborns ; developmental pharmacology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Aminophylline (theophylline-ethylenediamine) was administered to 27 premature newborns to prevent apneic spells. Of the 22 patients monitored for theophylline concentration, a therapeutic blood level was reached in 19 in 1–2 days, and 3 stayed below it. ‘Toxic’ blood levels (≥20 µg/ml) were reached in 3 cases, one of whom showed signs of toxicity. Theophylline treatment was not efficient in the prevention of apnea when a serious underlying disease was present. Theophylline blood half-life (mean : 27.0 h) and clearance (mean 12.9 ml/h/kg) confirmed the slow elimination pattern of the drug in the premature infant.
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  • 69
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 10 (1976), S. 291-309 
    ISSN: 1573-4889
    Schlagwort(e): tantalum alloy ; oxygen ; dissolution ; kinetics ; oxides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Oxygen was added to T-111 (Ta-8W-2Hf, wt.%) at 820 and 990°C at an oxygen pressure of about 3×10−4 Torr (4×10−2N/m2). The technique employed permitted predetermined and reproducible doping of T-111 up to 3.0 at% oxygen. Based on the temperature dependence of the doping reaction, it is concluded that the initial rates of oxygen pickup are probably controlled by solution of oxygen into the T-111 lattice. Although hafnium oxides are more stable than those of tantalum or tungsten, analyses of extracted residues indicate that the latter oxides predominate in the as-doped specimens, presumably because of the higher concentrations of tantalum and tungsten in the alloy. However, high-temperature annealing promotes gettering of dissolved oxygen and of other oxides to form hafnium oxides. Small amounts of tantalum and tungsten oxides were still present after high-temperature annealing. Tungsten oxide (WO3) volatilizes slightly from the surface of T-111 at 990°C. The vaporization of WO3 has no apparent affect on the doping reaction.
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  • 70
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 11 (1977), S. 127-132 
    ISSN: 1573-4889
    Schlagwort(e): Duplex oxides ; copper oxidation ; kinetics ; oxygen partitioning
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The theory for the growth of a double oxide layer proposed by Yurek, Hirth, and Rapp, has been applied to copper using experimental rate-constant data obtained by Valensi. Calculated thicknesses of the layers agree very well with experimentally measured values.
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  • 71
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 9 (1975), S. 459-472 
    ISSN: 1573-4889
    Schlagwort(e): Cr ; oxidation ; kinetics ; Cr2O3 grain size ; short-circuit diffusion ; surface ; preparation ; Fe-Cr
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Cr was oxidized in 1 aim O2 at 980, 1090, and 1200°C. ElectropolishedCr and some orientations of etched Cr oxidize rapidly and develop compressive stress in the growing Cr2O3; other orientations oxidize slowly, apparently free of stress. SEM examination of fracture sections shows that the thick oxide is polycrystalline whereas the thin oxide on etched Cr is monocrystalline. It is deduced that the monocrystalline oxide grows by lattice diffusion of cations outward, and the polycrystalline layer by the two-way transport of cation diffusion outward and anion diffusion inward along oxide grain boundaries. The consequent formation of oxide within the body of the polycrystalline layer generates compressive stress and leads to wrinkling by plastic deformation. The activation energy for oxidation of Cr by cation lattice transport is 58 kcal/mole. Polycrystalline Cr2O3 forms on Fe-26Cr alloy, whether electropolished or etched; oxidation is accordingly rapid and accompanied by compressive stress.
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  • 72
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 10 (1976), S. 85-95 
    ISSN: 1573-4889
    Schlagwort(e): boron carbide ; oxidation ; kinetics ; chromatography method
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Thermogravimetry and gas-adsorption chromatography were used to study the kinetics of formation of solid and gaseous products during the hightemperature oxidation of compact boron carbide in oxygen at 740 Torr. Oxidation resistance was observed at temperatures up to 1200°C. The main oxidation products were B2O3 and CO2. Oxidation was paralinear; the carbon consumption exceeded the consumption of boron as compared to the ratio of these elements in the compound B4C. This difference resulted in carbon depletion of the carbide layer in the substrate near the scale〉.
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  • 73
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 10 (1976), S. 361-376 
    ISSN: 1573-4889
    Schlagwort(e): metals ; scale structure ; epitaxy ; kinetics ; diffusion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract An explanation of the deviation from the parabolic law is the treatment which considers both shortcircuit and lattice diffusion in the oxide scale. In this study we examine how the oxidation kinetics are influenced by changing the structure of the scale of copper oxide in order to confirm the role of short-circuit diffusion in determining the oxidation rate. In addition we explain the oxidation kinetics of copper and nickel by using a model of the scale structure which includes recrystallization and grain growth. Results are as follows: (1) The nucleation and growth behavior of oxide have a direct effect on the structure and in turn the oxidation kinetics due to short-circuit diffusion. (2) A modified treatment is valid in the region where volume diffusion and short-circuit diffusion play an important role in which it is necessary to consider the scale structure such as the grain size distribution and the boundary width. (3) When recrystallization takes place it is necessary to consider the model of a two-layered scale structure which is different in properties and morphology. (4) In this region the rate curves are S-shaped when oxide recrystallization takes place and exhibit a transition from a parabolic to an nth-power relationship (n〉2) when grain growth takes place.
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  • 74
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 11 (1977), S. 225-239 
    ISSN: 1573-4889
    Schlagwort(e): tantalum ; oxidation ; high temperature ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation of tantalum in oxygen-nitrogen and oxygen-inert gas mixtures at925°C has been studied. The oxygen pressure was close to 0.5 atm in all experiments, and partial pressures of the second component of from 0 to 180 Torr were employed. Spherical specimens were used to provide quantitatively significant kinetic data. A model has been proposed which suggests that the oxygen pressure at the reaction interface close to the metal surface is lower than the external pressure because of the finite permeability of the porous outer oxide layer, and that the inert gas effectively reduces the permeability. The model gives good quantitative agreement with the experimental results.
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  • 75
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 11 (1977), S. 365-381 
    ISSN: 1573-4889
    Schlagwort(e): cobalt oxidation ; kinetics ; parabolic rate constant
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Precise values of parabolic rate constants of cobalt oxidation have been determined over a wide range of temperature (950–1300°C) and oxygen pressure (6.58× 10−4−0.658 atm). The dependence of the calculated values of parabolic rate constants k″p on oxygen pressure and temperature can be described by the following empirical equation: $$k''_p = const. \cdot {\text{p}}_{O_2 }^{{\text{1/n}}} \cdot exp ( - {\text{E}}_{\text{k}} /RT)$$ The exponent 1/n decreases with an increase in temperature from 1/3.40 at 950°C to 1/3.96 at 1300°C, whereas the activation energy Ek decreases with an increase in the oxygen pressure from 41.7 to 38.1 kcal/mole.
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  • 76
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 13 (1979), S. 77-88 
    ISSN: 1573-4889
    Schlagwort(e): BaTiO3 ; kinetics ; solid state
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The solid-state reaction between barium carbonate and rutile powders to form barium metatitanate BaTiO3 was studied by thermogravimetric analysis, X rays, and microscopy. Phase-stability domains were drawn in a temperature— $${\text{p}}_{CO_2 } $$ , diagram. The dependence of the reaction kinetics on $${\text{p}}_{CO_2 } $$ , $${\text{p}}_{O_2 } $$ or $${\text{p}}_{N_2 } $$ is discussed. In particular, the rate continuously decreases when $${\text{p}}_{CO_2 } $$ , or $${\text{p}}_{N_2 } $$ increases, but it reaches a maximum as a function of $${\text{p}}_{O_2 } $$ .
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  • 77
    ISSN: 1573-4889
    Schlagwort(e): Cu-Si alloys ; oxidation ; kinetics ; silica
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation of Cu-Si alloys (containing up to 4.75 wt. % Si) in $${\text{p}}_{O_2 } $$ =0.01 atm from 800 to 1000°C has been investigated using thermogravimetry and other techniques. A 0.04% Si alloy followed a parabolic oxidation law with a rate similar to that of pure Cu. As the Si concentration increased the rate decreased and became irregular owing to SiO2 particles or flakes at the alloy-scale interface. It is considered that sintering of SiO2 particles and rupture of the sinter because of contraction during sintering are responsible for the irregular kinetics. A SiO2 layer forms directly on the 4.75% Si alloy which oxidizes uniformly. The SiO2 was always amorphous. In pure CO2 a similar pattern of amorphous SiO2 particles, flakes, and layers occurs.
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  • 78
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 13 (1979), S. 283-298 
    ISSN: 1573-4889
    Schlagwort(e): oxidation ; surface alloys ; Fe-Cr alloys ; iron ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation behavior of several surface and bulk Fe-Cr alloys and iron at 300°C and 4×10−6 Torr oxygen was studied. The surface alloys were fabricated by implantation of 25 keV Cr ions into the outermost 300Å of polycrystalline iron samples. The oxide thickness as a function of oxygen exposure was obtained using proton-excited X-ray analysis, and composition profiles of oxide films were obtained using Auger electron spectroscopy and ion sputtering. The addition of Cr to Fe by surface and bulk alloying caused the oxidation rate to decrease and changed the oxidation kinetics from parabolic (for Fe) to logarithmic (for Cr concentrations ≥4.7at.%). Interpretation of the data in terms of simple oxidation theories indicates that the Cr additions may reduce the oxidation rate by altering the electronic properties of the metal-oxide interface.
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  • 79
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 13 (1979), S. 255-272 
    ISSN: 1573-4889
    Schlagwort(e): oxidation ; Fe-C ; graphite deposition ; nonadherent oxide ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation of Fe-C alloys containing 0.5 and 1.0% C was studied in 1 atm O2 at 700° C. The oxidation rate is considerably slower than for pure Fe. The oxide scale formed is detached, multilayered, and overoxidized, containing little or no FeO. A thin film of graphite was identified at the metal-oxide interface by electron diffraction. It is proposed that the slow oxidation and abnormal scale are caused by a residue of graphite left at the metal surface from the oxidation of Fe3C. This inhibition of the oxidation of Fe by carbon at 700°C is in contrast to the stimulation observed at 500°C.
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  • 80
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 13 (1979), S. 301-309 
    ISSN: 1573-4889
    Schlagwort(e): NiO ; Electrical conductivity ; gas-solid equilibria ; kinetics ; equivalent circuit
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract In a previous work it has been stated that the NiO electrical conductivity changes connected to the oxygen pressure changes may be considered as a transitory phenomenon. A mixed kinetics case controlled by the formation of surface cation vacancies and their diffusion in the bulk is proposed to explain the reaction process. By means of an equivalent electrical circuit in good agreement with the kinetics model it was possible to reproduce the experimental phenomenon.
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  • 81
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 13 (1979), S. 481-504 
    ISSN: 1573-4889
    Schlagwort(e): kinetics ; sulfidation ; Fe-Cr-Al alloys
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The influence of aluminium on the kinetics and mechanism of high-temperature sulfidation of Fe-Cr alloys containing 20 at.% chromium has been investigated. It has been found that the addition of aluminum greatly improves the scaling resistance of Fe-Cr alloys against attack by sulfur vapors at high temperatures.
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  • 82
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 9 (1975), S. 357-365 
    ISSN: 1573-4889
    Schlagwort(e): kinetics ; zirconia ; defect structure ; ionic conductivity ; yttria dopant
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract A Zr-0.5 Y alloy was found to oxidize about 6 times faster than pure zirconium over the temperature range of 400 to 565°C. The activation energies were nearly identical (∼32 kcal/mole). The activation energies correspond to grain boundary diffusion of oxygen through the scale. The higher oxidation rate of the alloy was attributed to a higher anion vacancy concentration and the assumption that diffusion sites in the lattice and boundaries were in local equilibrium. Measurements on yttria-doped zirconia showed that ionic conductivity was increased markedly by yttrium and extended over a wide range of oxygen pressure. The defect structure of the doped oxide was changed to one of oxygen vacancies, even at the high end of the oxygen pressure range, 10−8 to 0.2 atm, over which pure ziconia contains oxygen interstitials. The doped oxide was found to be extrinsic over the entire range of oxygen pressure and, although ionic conductivity predominated, electronic conductivity was still appreciable. The electronic conductivity, however, was still sufficiently high so that electron transport was not rate-controlling in the predominantly ionic-conducting scale.
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  • 83
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 10 (1976), S. 97-103 
    ISSN: 1573-4889
    Schlagwort(e): silicon carbide ; oxidation ; molecular oxygen ; glow-discharge oxygen plasma ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation kinetics and structure of the oxide scales formed on high-density SiC were studied in molecular oxygen at 740 Torr and in a glow-discharge oxygen plasma at 0.1 Torr at temperatures of 1000, 1100, and 1200°C. The monatomic oxygen formed by the glow discharge markedly increased the reaction rate and the vaporization of some of the oxidation products. The marked differences in kinetics suggest that the rate-controlling step during oxidation in molecular oxygen is the dissociation of adsorbed diatomic oxygen to the monatomic species. Films formed in molecular oxygen were mostly amorphous SiO2 with small inclusions of SiC and graphite, whereas films formed in dissociated oxygen were primarily amorphous SiO2 containing SiO, S2O3, and the coesite form of SiO2.
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  • 84
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 12 (1978), S. 215-225 
    ISSN: 1573-4889
    Schlagwort(e): oxidation ; Fe-Ni alloys ; kinetics ; scale morphology ; EPMA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation of an Fe—19.34 wt. % Ni alloy in dry CO2 has been studied at 700—1000°C using thermogravimetry, metallography, and EPMA. Weight gains for oxygen consumption followed a linear-parabolic-linear sequence at all temperatures. During the initial linear stage the scale consisted mainly of magnetite and the activation energy of 133±25 kJ · mole−1 is considered to be due to dissociation of CO2 into CO and adsorbed oxygen on the outer magnetite surface. During the parabolic oxidation stage a continuous Ni-rich layer containing ∼ 70% Ni forms a barrier to the diffusion which has an activation energy of 192±79 kJ · mole−1. The breakdown of the barrier layer causes a return to linear kinetics with an activation energy of 138±42 kJ · mole−1 for dissociation of CO2 on the outer surface. During the final linear stage there is pronounced general and intergranular subscale formation. Detailed information is presented of the Ni redistribution and concentrations during oxidation and its correlation with the kinetics and morphology.
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  • 85
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 9 (1975), S. 99-116 
    ISSN: 1573-4889
    Schlagwort(e): oxidation ; kinetics ; ilmenite ; rutile ; pseudobrookite
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation of ilmenite (FeTiO3) in air and dry oxygen was investigated over the temperature interval 600 to 970°C. Dense platelets of ilmenite crystals as well as powder samples of ilmenite were oxidized. The weight data were recorded employing a thermobalance. The oxidation kinetics of ilmenite platelets were parabolic except for the initial stages during which logarithmic kinetics were observed. For powder samples the logarithmic rate law was followed primarily. The logarithmic rate law was attributed to free penetration of oxygen through cracks and short-circuit paths. The activation energies associated with the logarithmic rate law were nearly one-half of those obtained from parabolic oxidation. The growth morphology of the products of oxidation of ilmenite was observed with a scanning electron microscope. The effect of growth morphology on the kinetics is discussed, and a probable reaction mechanism is suggested for the oxidation of ilmenite.
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  • 86
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 9 (1975), S. 441-450 
    ISSN: 1573-4889
    Schlagwort(e): kinetics ; cobalt and nickel oxidation ; parabolic rate constant
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract A new fast method is proposed for the determination of parabolic rate constants of metal oxidation as a function of pressure and temperature. The method consists of determining rate constants by oxidation of a single metal sample in a continuous manner, periodically changing the oxidant pressure or temperature. This method eliminates a number of errors inherent in the classical method which involves the use of a new metal specimen in each experiment and it further shortens the time of evaluating the functions k p '' = f (p, T). The method is particularly suitable for the determination of rate constants of slow processes. To verify the proposed method measurements of the kinetics of oxidation of cobalt and nickel at different oxygen pressures over the temperature range 1000–1300° C were carried out.
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  • 87
    ISSN: 1573-4889
    Schlagwort(e): kinetics ; oxidation ; microcalorimetry ; thermogravimetry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract In the kinetic theories of Bodenstein or Semenov the expression for the rate of a chemical reaction with several elementary stages can be expressed by different physical parameters. If two experimental methods are used, one method of necessity being microcalorimetry to measure the thermal flux produced by the reaction, it is possible to distinguish a pure kinetics case from a mixed one. The two-method technique has been verified by a study of the oxidation of niobium.
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  • 88
    ISSN: 1573-4889
    Schlagwort(e): titanium ; nitridation ; kinetics ; diffusion ; scaling
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The nitridation behavior of titanium has been examined in an atmosphere of nitrogen over the temperature range 900–1000° C. In addition to determining the reaction kinetics, microhardness and metallographic studies have been carried out on the nitrided substrates and nitride scales. Overall parabolic kinetics were exhibited, while a linear scaling reaction (associated principally with Ti2N formation) was observed. Extensive dissolution of nitrogen in the substrate was evident from the microhardness studies, and at 950 and 1000° C the growth of the nitrogen-stabilized αTi phase layer followed a parabolic law. Consideration of all the observed processes and derived data suggested that diffusion of nitrogen in the metal substrate was probably the rate-controlling mechanism.
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  • 89
    Digitale Medien
    Digitale Medien
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    Oxidation of metals 11 (1977), S. 263-276 
    ISSN: 1573-4889
    Schlagwort(e): nickel ; sulfidation ; kinetics ; mechanism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The reaction between pure nickel and H2S-H2 mixtures containing 1–65% H2S has been studied over the temperature range 450–600°C. The sulfidation of nickel in the temperature range 560–600°C has been found to follow a linear rate law at low concentrations of H2S and a parabolic rate law at higher concentrations (10% and 65% H2S); X-ray examination of the scale formed on the metal showed it to be almost entirely β-Ni3S2. On the basis of the kinetics and marker studies it can be concluded that the sulfide scale on nickel is formed by the outward transport of the metal and the inward transport of sulfur. In the temperature range 450–500°C the sulfidation of nickel follows a parabolic rate law. In mixtures containing 10% H2S the scale formed contains voids, the occurrence of which is connected with formation of Ni7S6. It has also been shown that the rate of transport through the Ni3S2 layer has an essential influence on the formation of a continuous layer of Ni7S6. Marker studies have shown that both nickel and sulfur appear to be mobile in β′-Ni3S2.
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  • 90
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 12 (1978), S. 67-82 
    ISSN: 1573-4889
    Schlagwort(e): oxidation ; Fe-C ; kinetics ; oxide grain size ; grain-boundary diffusion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Fe-C alloys containing 0.1, 0.5, and 1.0% C were oxidized in 1 atm O2 at 500°C. Two specimen preparations were used: annealed followed by slow cooling to form coarse pearlite plus proeutectoid ferrite or cementite; and cold-worked by abrading after annealing. The cold-worked alloys oxidize more rapidly. Annealed pearlite oxidizes faster than annealed ferrite. The differences in oxidation rate are caused by differences in the Fe3O4 grain size, that is, by the number of oxide grain boundaries available to act as easy diffusion paths for the outward diffusion of Fe through the Fe3O4. The oxidation rate constant is 10 times larger for fine-grained poly crystalline oxide than for oxide in which the Fe3O4 is monocrystalline.
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  • 91
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 13 (1979), S. 437-456 
    ISSN: 1573-4889
    Schlagwort(e): Fe-Cr ; oxidation ; kinetics ; oxide morphology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Ferritic polycrystalline Fe-24 wt.% Cr was oxidized in pure oxygen at 190 ≤ T≤490° C and pressures in the range 5.3×10−2–13.3 Pa for periods of up to 5 hr. The reaction proceeded in three stages. An initial period of accelerating rate was accompanied by oxide island nucleation and growth. Following island coalescence the rate was approximately logarithmic at low temperatures and somewhat slower than parabolic at high temperatures. Rate control during this period was thought to be due to mass transport through the oxide grain boundaries left by the island impingement process. During these first two stages the oxide formed was γ-M2O3 with possibly some spinel. The final stage of reaction involved the appearance of α-M2O3 on the outer oxide surface and a substantial slowing of the oxidation rate due to the low diffusivity in this phase.
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  • 92
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 13 (1979), S. 89-104 
    ISSN: 1573-4889
    Schlagwort(e): BaTiO3 ; kinetics ; solid state ; mechanisms
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The authors propose a mechanism for the solid-solid reaction BaCO3+ TiO2→BaTiO3+CO2. This mechanism is based on the real structure of the present semiconductors. The reactions at different interfaces and the diffusing species are identified. The reaction rates are calculated and the dependence of the reaction rate upon O2, N2, and CO2 gas pressure is interpreted and discussed.
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  • 93
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 13 (1979), S. 119-158 
    ISSN: 1573-4889
    Schlagwort(e): nickel-chromium alloys ; oxidation ; high temperature ; kinetics ; mechanisms
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation of binary Ni-Cr alloys containing 44 and 50 wt. % Cr has been studied over a range of oxygen partial pressures at temperatures between 800 and 1100°C. The effects of cold work, surface preparation, and distribution of the Cr-rich second phase have been studied. The oxidation behavior is complex and cannot be described by a single model. The oxide grows by short-circuit diffusion as well as bulk transport through Cr 2 O 3 scales. The scale-growth mechanism includes extensive metal-oxide separation requiring Cr vapor transport to the scale, compressive stresses within the oxide which result in scale bulging and cracking, and the formation of a second oxide layer which results in voids being incorporated into the scale. Any factor which reduces the oxide grain size, such as cold work, finer distribution of the Cr-rich α phase or reduced oxygen pressure, results in an increased oxidation rate of binary alloys because of an increased number of grain-boundary short-circuit diffusion paths.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 94
    Digitale Medien
    Digitale Medien
    Springer
    Journal of pharmacokinetics and pharmacodynamics 3 (1975), S. 277-290 
    ISSN: 1573-8744
    Schlagwort(e): sulfobromophthalein (BSP) ; kinetics ; BSP disposition ; mathematical model ; flow-limited
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A linear, flow-limited mathematical model of drug kinetics was used to simulate total sulfobromophthalein (BSP) kinetics in normal anesthetized rats during intravenous infusions and following rapid intravenous injections. Four parameters were used to characterize the distribution and biliary and urinary excretion of BSP: liver- to- plasma concentration ratio, extrahepatic tissue- to- plasma concentration ratio, liver clearance rate constant, and renal plasma clearance rate constant. The same parameters appear to characterize the kinetics of BSP in man through the successful application of “scale- up” techniques utilizing data from experiments in rats. Plasma levels of BSP corresponding to intravenous infusions and rapid intravenous injections in man are approximated by computer simulation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 95
    Digitale Medien
    Digitale Medien
    Springer
    Journal of pharmacokinetics and pharmacodynamics 5 (1977), S. 183-192 
    ISSN: 1573-8744
    Schlagwort(e): propranolol ; kinetics ; volunteers ; bioavailability ; threshold dose
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The pharmacokinetics of propranolol in blood was studied in healthy volunteers, following intravenous administration of 0.1 mg/kg and increasing oral doses of 10,20, and 40 mg, using a specific and sensitive gas Chromatographie method. The systemic availability of orally administered propranolol varied from 9% to 38% between subjects, but it was constant within each subject. A linear relationship was found between the area under the blood concentration-time curve and the oral dose. At variance with literature data, we could not observe a threshold dose.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 96
    Digitale Medien
    Digitale Medien
    Springer
    Journal of pharmacokinetics and pharmacodynamics 6 (1978), S. 389-397 
    ISSN: 1573-8744
    Schlagwort(e): probenecid ; methotrexate ; cerebrospinal fluid ; kinetics ; interaction ; dogs ; choroid plexus ; intrathecal
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Probenecid is known to inhibit the renal excretion of methotrexate (MTX) and the transport of organic anions by the choroid plexus of the brain. The effect of probenecid on the CSF clearance of MTX given by the intrathecal route was examined in anesthetized dogs. Plasma and CSF MTX levels were measured following intrathecal injection of 0.4 mg/kg MTX, with and without pretreatment with probenecid. In the absence of probenecid, the peak plasma MTX concentration of 3.18×10−7±1.09×10−7 M (mean±SD) was reached 5 hr after intrathecal injection. With probenecid pretreatment, the mean peak plasma MTX concentration was lower (2.09×10−7+-0.98×10−7 M) and plasma disappearance was prolonged. A biexponential decay of CSF MTX levels was observed over the duration of sampling. The half-life of the second exponential phase was 21 hr without probenecid pretreatment and was longer after probenecid pretreatment. These results provide strong evidence that probenecid inhibits transfer of MTX from CSF to plasma following intrathecal injection.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 97
    Digitale Medien
    Digitale Medien
    Springer
    Journal of pharmacokinetics and pharmacodynamics 7 (1979), S. 557-578 
    ISSN: 1573-8744
    Schlagwort(e): kinetics ; enzyme induction ; drug interaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Equations were derived to describe the time course of drug levels during auto- and heteroinduction under a variety of input conditions. These equations were based on a pharmacokinetic theory of induction which assumes that metabolic clearance increases exponentially to a maximum value and that the rate of this increase is governed by the degradation rate constant of the induced enzyme (k′). Closed form solutions could be obtained only for intravenous single-dose (case I) and multiple-dose (case IV) administration. For each of the other cases, constant-rate intravenous infusion (case III), oral single-dose administration (case II), and multiple-dose administration (case V), an exact solution (not closed form) and an approximation (closed form) were derived. Two sets of equations were derived for each of the five cases to take into consideration the possibility of a latency term (λ).Plots of drug amount X(or concentration C) vs. time (t) were constructed. In case I, a log Xvs. tplot was convex, the slope increasing with time. In case II, Xincreased,reached a peak, and decayed as in case I. In case III (λ 〉 5In 2V/Q) Creached a preinduction steady state before decreasing to a lower (induced) steady state. When λ=0, Creached a maximum before decreasing to the same induced steady state. The behavior of Cvs. tfor cases IV and V was similar to that for case III. Determination of parameters was attempted in case III. Nonlinear least-square fitting of generated data with 3–9% error yielded reasonable estimates of k′.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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