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  • Artikel  (63)
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  • Springer  (63)
  • American Institute of Physics
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  • 1995-1999  (27)
  • 1990-1994  (36)
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  • 1
    Digitale Medien
    Digitale Medien
    Static and dynamical distortions of helium clusters (1995)
    Springer
    The European physical journal 98 (1995), S. 421-428 
    Details
    ISSN: 1434-6036
    Schlagwort(e): 36.40.+d ; 33.70.Jg ; 67.40.Yv
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We examine the effects of impurities (“doping”) and rotational excitation on the structural and energetic properties of helium clusters. Quantum Monte Carlo (QMC) techniques are used to study ground and rotationally excited states of pure and doped clusters. We use exponentially correlated wave functions and treat the molecular impurities as rigid. Whereas pure HeN show essentially monotonic decay of density from a central maximum value, addition of impurities induces local ordering of He to an extent dependent on the impurity-He binding. Rotational excitation of HeN gives rise to extremely large centrifugal distortions. The location of impurities also appears to change upon rotational excitation. The implications of these distortions on impurity spectra are discussed for SF6HeN, and compared to recent experimental results.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01338418
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  • 2
    Digitale Medien
    Digitale Medien
    LIDAR multiple scattering from clouds (1995)
    Springer
    Applied physics 60 (1995), S. 355-362 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Multiple-scattering LIDAR return calculations obtained by seven different models for the same specified numerical experiment are compared. This work results from an international joint effort stimulated by the workshop group called MUSCLE for MUltiple SCattering Lidar Experiments. The models include approximations to the radiative-transfer theory, Monte-Carlo calculations, a stochastic model of the process of multiple scattering, and an extension of Mie theory for particles illuminated by direct and scattered light. The model solutions are similar in form but differ by up to a factor of 5 in the strength of the multiple-scattering contributions. Various reasons for the observed differences are explored and their practical significance is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01082271
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  • 3
    Digitale Medien
    Digitale Medien
    Analytical multiple-scattering extension of the Mie theory: The LIDAR equation (1995)
    Springer
    Applied physics 60 (1995), S. 331-334 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Multiple scattering of light in aerosol media is described in a simple picture within the framework of Mie theory. Our approach leads to an analytical expression of then-fold scattered electromagnetic field and then to an analytical derivation of multiple-scattering LIDAR equation form transport theory. This approach differs from both the descriptions of multiple scattering based on the approximation of radiative-tranfer theory and from statistical approaches mainly based on Monte-Carlo calculations. The physical quantities of interest are expressed by straightforward generalization of the corresponding single-scattering quantities. Therefore, the multiple-scattering contributions are calculated without losing the advantage of working with analytical expression in the frame of Mie theory.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01082267
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  • 4
    Digitale Medien
    Digitale Medien
    Influence of spatial mode matching in end-pumped solid state lasers (1992)
    Springer
    Applied physics 54 (1992), S. 83-88 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.60 ; 42.60.F ; 42.60.K
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We present investigations on the influence of mode matching on the efficiency of longitudinally pumped solid state lasers. In a theoretical part we enhance an existing model for four level lasers from idealized cylindrical modes to arbitary pump and laser modes in a random relative position thereby neglecting beam deformation due to thermal effects. The theoretical predictions were confirmed experimentally with an end-pumped Nd:YAG rod operated at 1064 nm. To investigate the effect of misalignment on the efficiency we used a Ti-Sapphire pump laser which was displaced relative to the laser beam. To establish the influence of arbitary pump modes on laser performance a diode laser equipped with coupling optics served as pump source for the same resonator. The resulting decrease in slope efficiency compared to the Ti-Sapphire pumped system could be explained in terms of limited mode overlap due to the characteristic pump field distribution produced by the diode coupling optics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00331738
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  • 5
    Digitale Medien
    Digitale Medien
    LCVD of tungsten microstructures on quartz (1992)
    Springer
    Applied physics 54 (1992), S. 189-192 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.60 ; 81.15 ; 82.00
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The pyrolytic laser-induced chemical vapor deposition (LCVD) of tungsten microstructures in the form of spots has been investigated. Fused quartz substrates and a mixture of WF6 and H2 have been employed in the experiments. Different shapes of spots related to different partial pressures of WF6 and H2 have been revealed. The results can qualitatively be described by a combination of surface reactions and gas-phase reactions resulting in tungsten deposition and surface etching.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00325499
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  • 6
    Digitale Medien
    Digitale Medien
    Gain depletion due to amplified spontaneous emission in multi-pass laser amplifiers (1992)
    Springer
    Applied physics 54 (1992), S. 506-512 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.60 ; 42.55.Gp
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Calculations of the effects of amplified spontaneous emission (ASE) in laser amplifiers designed to amplify sub-picosecond pulses are presented. A one-dimensional code is used with some simple approximations to account for aspect ratio variation in cases of cylindrical symmetry. Gain depletion due to ASE is compared for various multi-pass geometries. Optimisation for short pulse amplification of a telescopic, beam-expanding, 4-pass amplifier is considered.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00325517
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  • 7
    Digitale Medien
    Digitale Medien
    Achievement of laser fusion of biological cells using UV pulsed dye laser beams (1992)
    Springer
    Applied physics 54 (1992), S. 531-533 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 07.60 ; 42.60 ; 42.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract This paper reports a successful achievement of laser-induced biological cell fusion using an excimer laser excited dye laser. To our knowledge, we examined for the first time the dependence of fusion rate on laser pulse energy, number of laser pulses, and laser wavelength. Maximum fusion rate of approximately 50% was obtained by this laser fusion technology.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00325521
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  • 8
    Digitale Medien
    Digitale Medien
    Multiple breakdown in helium generated by hybrid 10 μm Co2 laser pulses (1992)
    Springer
    Applied physics 54 (1992), S. 526-530 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 52.00 ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract In this paper we describe the experimental investigation of the post-breakdown development of a helium plasma generated by a hybrid 10 μm CO2 laser pulse. As a result we found that a long tail and a high energy of the CO2 laser pulse cause multiple successive breakdown in the gas. We have measured the time to the first breakdown and the time between first and second breakdown as functions of gas pressure and laser pulse peak intensity as well as the spatial intensity distribution of the transmitted laser pulse. Among the relevant mechanisms self-focusing is not observed before the second breakdown.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00325520
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  • 9
    Digitale Medien
    Digitale Medien
    Test of an optical parametric oscillator (OPO) as a compact and fast tunable stokes source in coherent anti-stokes raman spectroscopy (CARS) (1992)
    Springer
    Applied physics 55 (1992), S. 378-380 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.60 ; 42.65 ; 42.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract An optical parametric oscillator (OPO), as a novel kind of broadband Stokes source, is employed for coherent anti-Stokes Raman spectroscopy (CARS). Compared to the conventional dye laser configuration OPO-CARS offers practical advantages. The tunable OPO allows a fast and comfortable frequency tuning. The excitation bandwidth of about 35 cm−1 (FWHM) limits the spectral range of effective and stable single pulse CARS generation but can be used to enhance selected spectral structures.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00333085
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  • 10
    Digitale Medien
    Digitale Medien
    Multi-megawatt superradiant emissions from coumarin-doped sol-gel derived silica (1992)
    Springer
    Applied physics 55 (1992), S. 365-367 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.55.Mv ; 42.55.Rz ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Fluorescence and lasing properties of coumarindoped silica samples prepared by sol-gel process were investigated. Superradiant emissions at peak power as high as 7MW were measured at around 535 nm when the silica samples were excited by a XeF laser. The energy of the superradiant pulse was 89 mJ, corresponding to a conversion efficiency of 36.6%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00333082
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  • 11
    Digitale Medien
    Digitale Medien
    Preionization effects of iso-C4H10 in N2 TE UV lasers (1992)
    Springer
    Applied physics 55 (1992), S. 433-436 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract In this paper the ionizing role of isobutane (iso-C4H10) in the operation of a N2TE UV laser is analyzed. Laser pulse width value modifications, different laser wavelengths generated in the 2+ system and voltage pulse period modifications are analysed in order to show that isobutane, in very reduced quantities, generates a preionizing effect that can be higher than that produced by a conventional wire preionization system.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00325183
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  • 12
    Digitale Medien
    Digitale Medien
    Continuous-wave mode-locked solid-state lasers with enhanced spatial hole burning (1995)
    Springer
    Applied physics 61 (1995), S. 429-437 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.60 ; 42.55 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We systematically investigate the difference between both actively and passively mode-locked lasers with Gain-at-the-End (GE) and Gain-in-the-Middle (GM) at the example of Nd:YLF lasers. The GE laser generates pulse widths approximately three times shorter than a comparable GM cavity. This is due to enhanced Spatial Hole Burning (SHB) which effectively flattens the saturated gain and allows for a larger lasing bandwidth compared to a GM cavity. We first investigate enhanced SHB by measuring the cw mode spectrum, where we have observed that the mode spacing in GE cavities depends primarily on the crystal length. This was also confirmed for a Nd:LSB crystal, where the pump absorption length was significantly shorter than the crystal length. In mode-locked operation, pulse widths of 4 ps for passive mode locking and 5 ps for active mode locking are demonstrated with GE cavities, compared to 11 ps for passive and 17 ps for active mode locking with GM cavities. Additionally, the time-bandwidth product for the GE cavity is approximately twice the ideal product for a sech2 pulse shape and cannot be improved by dispersion compensation alone, while the GM cavity has nearly ideal time-bandwidth-limited performance. The results for the GM cavity compare well to existing theories taking into account the added effect of pump-power-dependent gain bandwidth which increases the bandwidth of Nd: YLF from 360 to 〉 500 GHz. In a following paper [1] (called Part II) a rigorous theoretical treatment of the effects due to SHB will be presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081271
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  • 13
    Digitale Medien
    Digitale Medien
    Multiple scattering of narrow light beams in aerosols (1995)
    Springer
    Applied physics 60 (1995), S. 315-323 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A multiple scattering propagation model of narrow light beams in aerosol media is described. It is based on a paraxial approximation of the radiative transfer equation in which the flux normal to the incident beam direction is modeled by a diffusion process. The model solutions are the forward- and backscattered intensity profiles for the specified geometry and receiver aperture and field of view. The required inputs are the system parameters, and the aerosol single scattering angular phase function and extinction and scattering coefficients which are allowed to vary along the beam axis. Good agreement is shown with measurements performed in the laboratory over scales ranging from a few tens of mm to a few m, and in the atmosphere over a scale of the order of 1 km. The solutions are valid for optical depths smaller than ≈ 10, for phase functions corresponding to average size parameters of order one or greater, and for off-axis positions not exceeding ≈ 25% of the reciprocal of the scattering coefficient.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01082265
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  • 14
    Digitale Medien
    Digitale Medien
    Accurate measurement of ultralow loss in a high-finesse Fabry-Perot interferometer using the frequency response functions (1995)
    Springer
    Applied physics 61 (1995), S. 9-15 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 06.00 ; 07.60 ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We describe the accurate measurement of ultralow loss in a high-finesse Fabry-Perot interferometer using a diode-pumped Nd:YAG laser locked to the longitudinal mode with an active frequency-stabilization technique. By measuring the resonance full width and the free spectral range with the frequency response functions, and by measuring the transmission efficiency on resonance, the finesse and the loss at 1064 nm are accurately measured to be 78100 ± 1200 (reflectance of 99.99598 ± 0.00006%) and 1 5.9 ±2.0 × 10−6 (15.9 ± 2.0 ppm), respectively.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01090966
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  • 15
    Digitale Medien
    Digitale Medien
    Spectral properties of diode-pumped non-planar monolithic Nd:YAG ring lasers (1995)
    Springer
    Applied physics 61 (1995), S. 243-248 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.55 ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The coherence length of a single-frequency monolithic Nd:YAG ring laser is determined by using a highly unbalanced all-fiber Mach-Zehnder interferometer. A coherence length larger than ⋍ 1500km and a 3 dB linewidth less than ⋍ 60 Hz is estimated. Furthermore, an easy method to measure the temperature dependence on several laser parameters is described. This method is based on the laser emission in multiple axial modes, which is enforced by coherent optical feedback. A model explaining the multimode behaviour is presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01082042
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  • 16
    Digitale Medien
    Digitale Medien
    Development of a dual-wavelength dye-laser system for the UV and its application to simultaneous multi-element detection (1995)
    Springer
    Applied physics 61 (1995), S. 339-343 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.60 ; 42.65 ; 82.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract In this paper, the design and performance characteristics of a pulsed tunable dye laser system for the simultaneous generation of two UV wavelengths are presented. The system is composed of an oscillator and an amplifier stage, pumped by the second harmonic of a commercial Nd:YAG laser. Dual-wavelength operation is achieved with one additional tuning mirror introduced to the prism expanded grazing incidence oscillator. The two obtained wavelengths are independently tunable, their separation is only limited by the gain profile of the dye. Both wavelengths are frequency doubled by Second-Harmonic Generation (SHG) in two KDP or BBO crystals. Performance characteristics such as bandwidth, efficiency, tuning range and wavelength separation are reported. As application two such systems are used for the simultaneous detection of the four elements cadmium, nickel, manganese and lead by Laser-Excited Atomic Fluorescence Spectrometry in a graphite furnace (ETA-LEAFS).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081533
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  • 17
    Digitale Medien
    Digitale Medien
    CARS diagnostics of a CO2-laser pyrolytic experiment for the production of nanosized ceramic powders (1995)
    Springer
    Applied physics 61 (1995), S. 367-375 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 36.40.+d ; 42.65.Dr
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Spatial distributions of rotational temperatures and molecular number densities of C2H2 and H2 were measured with CARS during the production of ultrafine SiC powders in a laser pyrolytic process flame. By means of a CO2 laser, the reaction gases SiH4 and C2H2 (or alternatively C2H4) are converted into SiC and H2. From the CARS measurements temperature gradients are determined between 8.8 × 105 K/m and 1.6 × 106 K/m with corresponding heating rates of 1.8 × 106 K/s and 1.3 × 106 K/s. The CARS data also allow an estimation of the gas expansion behaviour in the reaction zone. Moreover, they show that diffusive velocity components of the hydrogen in the hot reaction zone do not exceed 0.4 m/s.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081537
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  • 18
    Digitale Medien
    Digitale Medien
    Direct observation of the second-order Stark effect of theX-B transition in molecular iodine (1995)
    Springer
    Applied physics 60 (1995), S. 43-45 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 07.60 ; 07.65 ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The second-order Stark shift of the components of the hyperfine structure of the transition1∑ g + (υ″ = 0,j″ = 13, 15) →3∏ ou + (υ′ = 43,j′ = 12, 16) (of molecular iodine have been studied by means of saturated absorption spectroscopy in an external cell with the I2 vapour located in an electric field. The anisotropic polarizabilities of the upper and lower levels together with the difference between the isotropic polarizabilities of the levels of the transition have been obtained.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01082071
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  • 19
    Digitale Medien
    Digitale Medien
    High energy negative feedback controlled passively mode-locked Nd: YAG laser (1992)
    Springer
    Applied physics 54 (1992), S. 231-233 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract High energy picosecond pulse trains from a passively mode-locked Nd: YAG laser are obtained. The negative feedback controlled oscillator delivers 10–30 μs trains with energies of up to 30 mJ and single pulse duration of less than 25 ps. The laser is operated with a repetition rate of 10 Hz. An active Q-control of the cavity generates a short pulse train with duration of 30–40 ns. The long pulse train energy reproducibility is better than ± 1.5%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00325508
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  • 20
    Digitale Medien
    Digitale Medien
    Axially phase-matched parametric four- and six-wave mixing in potassium vapor (1992)
    Springer
    Applied physics 54 (1992), S. 288-294 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.60 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Systematic experimental observations of axially phase-matched parametric four- and sixwave mixing processes have been made in potassium vapor pumped on or near the 4S–6S two-photon resonance. An IR up-conversion with a beta barium borate crystal was used for the detection of IR emissions. All the predicted processes have been observed. It is found that the excitation spectra of the emissions for those processes observed in this work are quite different from the excitation spectra of similar processes in sodium vapor. A dye-dependence of some emissions generated by the axially phase-matched parametric six-wave mixing processes has been found by using different dyes in the dye laser. The reason for the dye-dependence is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00325194
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  • 21
    Digitale Medien
    Digitale Medien
    Output power enhancement of the 632.8 nm monomode He-Ne/I2-laser (1992)
    Springer
    Applied physics 54 (1992), S. 307-308 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.55 ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract For the He-Ne/I2-laser, a stable monomode operation has been realized when the tube pressure exceeds a certain level. An output power of more than 1 mW has been obtained at the 632.8 nm laser transition. Within the monomode tuning range of the laser, the d, e, f, g, and h, i, j iodine hyperfine components of the R(127) line of the 11–5 band of the B 3 II + 0u−X 1Σ+ 0g electronic transition have been observed. The mode selection method used makes it possible to increase the contrast of the iodine hyperfine components.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00325197
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  • 22
    Digitale Medien
    Digitale Medien
    Ti:Sapphire-pumped femtosecond optical parametric oscillators based on KTiOPO4 and RTiOAsO4 (1995)
    Springer
    Applied physics 60 (1995), S. 437-442 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.55 ; 42.65 ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The design, configuration and operation of Ti:Sapphire-laser-pumped femtosecond Optical Parametric Oscillators (OPOs) using KTP and RTA are described. The results presented include configurations capable of producing transform-limited pulses shorter than 40 fs and operating with pump powers as low as 50 mW. Tunability within the 1–3 µn spectral region is demonstrated using pump-tuning alone.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081323
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  • 23
    Digitale Medien
    Digitale Medien
    New UV tunable solid-state lasers for lidar applications (1995)
    Springer
    Applied physics 61 (1995), S. 117-120 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.55 ; 42.60 ; 92.60 ; 92.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We present the first lidar/DIAL system based on an Ultra Violet (UV) vibronic laser. A Nd:YAG-pumped Ce:LiSAF laser has been developed for this purpose, providing high pulse energy (5 mJ at 10 Hz), very high slope efficiency (33%), and a tuning range from 284 to 299 nm. Simultaneous measurements of SO2 and O3 concentration profiles are presented using this frequency-agile Ce:LiSAF-based lidar system.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01090981
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  • 24
    Digitale Medien
    Digitale Medien
    Continuous-wave mode-locked solid-state lasers with enhanced spatial hole burning (1995)
    Springer
    Applied physics 61 (1995), S. 569-579 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.60 ; 42.55 ; 42.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract In Part I of this paper [1] experimental results were presented and discussed. In this part, we investigate theoretically the dynamics of end-pumped solid-state lasers due to enhanced spatial hole burning. This becomes possible by a fast numerical implementation of the saturated gain in the presence of strong spatial hole burning that allows to treat the multimode case for an arbitrary pumping level. We find for a wide range of laser parameters that the mode spacing of the cw running modes is essentially determined by the length of the gain medium and only weakly depends on the absorption depth of the pump transition. It is shown that spatial hole burning can lead to a completely flat saturated gain profile over half of the gain bandwidth. In mode-locked lasers, the flat gain due to spatial hole burning results in shorter pulses. But the pulses are neither Gaussian-nor sech-shaped as they are in actively or passively mode-locked lasers without spatial hole burning. Further, we show that soliton-like pulse shaping can be used to restore a transform-limited sech-shaped pulse in an end-pumped solid-state laser while exploiting the full gain bandwidth of the laser material.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01091215
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  • 25
    Digitale Medien
    Digitale Medien
    Solid-state dye lasers based on copolymers of 2-hydroxyethyl methacrylate and methyl methacrylate doped with rhodamine 6G (1995)
    Springer
    Applied physics 60 (1995), S. 383-389 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.55.Rz ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Rhodamine 6G has been dissolved in copolymers of 2-HydroxyEthyl MethAcrylate (HEMA) and Methyl MethAcrylate (MMA) and the resulting solid-state solutions have been pumped at 337 nm and 532 nm. Lasing efficiencies similar to those found in ethanol solution have been obtained with a 1:1 vol/vol HEMA: MMA copolymer matrix, and lifetimes of ca. 10 000 (337 nm pumping) and ca. 75 000 (532 nm pumping) pulses at repetition rates up to 15 Hz and 10 Hz, respectively, have been demonstrated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01082275
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  • 26
    Digitale Medien
    Digitale Medien
    Short-term frequency stabilization of diode-laser-pumped Nd:YAG lasers using double-pendulum suspended cavities (1995)
    Springer
    Applied physics 60 (1995), S. 489-494 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 07.60 ; 42.50 ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We describe the improvement of short-term frequency stability of diode-laser-pumped Nd:YAG lasers. To improve the vibrational isolation of reference cavities, the reference cavities were suspended by a double pendulum with magnetic damping. The frequency noise was reduced to lower than 1 Hz/√Hz at Fourier frequencies higher than 5 Hz and the minimum noise of 7 × 10−3 Hz/√Hz was recorded. The minimum root Allan variance was about 10−14 for the sampling time of 0.01 s. Heating of the reference cavity by absorbed laser power caused the thermal drift of cavity resonance frequencies. It resulted in the laser linewidth in the range of 30–50 Hz.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01081332
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  • 27
    Digitale Medien
    Digitale Medien
    Optimization of multiple-pass off-axis KrF amplifiers (1995)
    Springer
    Applied physics 60 (1995), S. 565-570 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Multiple-pass short-pulse off-axis amplification using spherical and cylindrical expansion schemes has been analyzed for different conventional discharge-pumped KrF gain modules. It is shown that using a single-gain module in a three-pass optimized off-axis arrangement, output energies up to several 1OO mJ can be reached with excellent contrast, starting from 10–20 µJ input energies.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01080936
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  • 28
    Digitale Medien
    Digitale Medien
    Short- and long-term frequency stabilization of a He-Ne laser using a Fabry-Perot cavity locked to the lamb dip (1992)
    Springer
    Applied physics 54 (1992), S. 202-204 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 07.60 ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We have developed a frequency-stabilization system for the He-Ne laser using an external Fabry-Perot cavity which is locked to the Lamb dip of the laser. The cavity serves as a frequency discriminator for high-frequency noise suppression, while the length of the Fabry-Perot cavity is controlled, reffered to the Lamb dip, in order to eliminate low-frequency fluctuations. The frequency noise of a laser stabilized with the cavity suspended in a vacuum tank can be suppressed to about 1 $$0.1Hz/\sqrt {Hz} $$ at around 100 Hz by an FM-sideband locking method. The oscillation frequency is fixed to the Lamb dip at low frequency by controlling the cavity length thermally. The frequency fluctuation around the Lamb dip was estimated to be ∼ 2.3 MHz.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00325502
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  • 29
    Digitale Medien
    Digitale Medien
    Detection of methane in air using diode-laser pumped difference-frequency generation near 3.2 μm (1995)
    Springer
    Applied physics 61 (1995), S. 553-558 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 07.65 ; 33.00 ; 42.60 ; 42.65 ; 42.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Spectroscopic detection of the methane in natural air using an 800 nm diode laser and a diode-pumped 1064 nm Nd:YAG laser to produce tunable light near 3.2 µm is reported. The lasers were pump sources for ring-cavity-enhanced tunable difference-frequency mixing in AgGaS2. IR frequency tuning between 3076 and 3183 cm−1 was performed by crystal rotation and tuning of the extended-cavity diode laser. Feedback stabilization of the IR power reduced intensity noise below the detector noise level. Direct absorption and wavelength-modulation (2f) spectroscopy of the methane in natural air at 10.7 kPa (80 torr) were performed in a 1 m single-pass cell with 1 µW probe power. Methane has also been detected using a 3.2 µm confocal build-up cavity in conjunction with an intracavity absorption cell. The best methane detection limit observed was 12 ppb m (Hz.)−1/2.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01091213
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  • 30
    Digitale Medien
    Digitale Medien
    The dimer sputtering mechanism of Cu(001) at low bombarding energy (1992)
    Springer
    Applied physics 55 (1992), S. 364-371 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 79.20.N ; 36.40.+d
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The emission of dimers during bombardment of a Cu(001) surface by Cu atoms of 300 and 1000eV energy is studied. A molecular dynamics simulation method based on many-body potentials is employed. At 300eV bombarding energy, around 81% of the sputtered dimers originate from second-nearest neighbor sites. 58% of these are ejected in a collision sequence correlated by the projectile. These dimers lead to a second maximum in the kinetic energy distribution of emitted dimers at around 8eV, besides a maximum at 4eV. Only the latter is found at 1000eV bombarding energy. As in this case mostly next-neighbor surface atoms are sputtered, the specific emission mechanism found at 300eV is irrelevant. Finally, we show that the direction of the angular momentum of sputtered dimers is correlated with the original surface site of the dimers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00324086
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  • 31
    Digitale Medien
    Digitale Medien
    Nanosecond and femtosecond excimer laser ablation of fused silica (1992)
    Springer
    Applied physics 54 (1992), S. 363-368 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.60 ; 42.70 ; 81.40
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Ablation of fused silica using standard excimer lasers (20–30 ns pulse duration at 193, 248, and 308 nm) and a short pulse laser system (500 fs at 248 nm) is reported. Ablation rates range from several hundred nm/pulse (193 nm or fs-laser) up to about 6 μm/pulse (308 nm). The performance of the ablation is found to depend not only on wavelength and pulse duration but also on the existing or laser induced surface quality (e.g., roughness) of the material. Special ablation phenomena are observed. At 193 nm and moderate fluence (3 J/cm2) ablation takes place at the rear side of a plate without affecting the front side, whereas at higher fluence normal ablation at the front side occurs. At 248 nm (standard excimer) the existence of two consecutive ablation phases is observed: smooth ablation at low rate is followed by explosive ablation at high rate. Using fs-pulses smooth shaped holes are formed during the first pulses, whereas high pulse numbers cause the development of a ripple structure in the ablation craters. The results lead to the conclusion that two different ablation mechanisms are involved: the first is based on two photon bulk absorption, the second on controlled surface damage in relation with (partially laser induced) singularity conditions at the surface.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00324203
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  • 32
    Digitale Medien
    Digitale Medien
    Structure formation in UV-laser-ablated polyimide foils (1992)
    Springer
    Applied physics 55 (1992), S. 119-120 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.60 ; 61.40 ; 68.35
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The formation of nap-type and wall-type structures on laser-irradiated polyimide (PI) films is reported for the first time. These investigations demonstrate that such structures can develop on non-melting polymer surfaces.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00324612
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  • 33
    Digitale Medien
    Digitale Medien
    Photokinetic etching of polyethylene terephthalate films by continuous wave ultraviolet laser radiation (1992)
    Springer
    Applied physics 55 (1992), S. 269-273 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.60 ; 82.65 ; 73.40
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Continuous wave laser radiation from an argonion laser in the wavelength range 275–330 nm can be used to etch polyethylene terephthalate (PET) films with as little thermal damage as from a pulsed, ultraviolet laser (248 nm or 308 nm) provided the beam is focussed to a spot of 10–100 kW/cm2 of power density and is moved over the surface at speeds at which the transit time over its own diameter (which can be looked upon as a “pulse width”) is on the order of 10–200 μs. In contrast to results which had been obtained previously on the photokinetic etching of polyimide and doped polymethyl methacrylate films under similar conditions, the sensitivity of PET to etching is 〉5-fold greater than either of these polymers and increases steadily with increasing pulse width. There is lateral thermal damage as the pulse widths increase to 〉200 μs. The material that is removed is vaporized in part. More than 20% is probably ejected in a molten state and resolidifies at the edge of the cut. There is no acoustic report similar to that seen in ablative photodecomposition. The process appears to be largely thermal in nature.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00348396
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  • 34
    Digitale Medien
    Digitale Medien
    Nanosecond and femtosecond excimer-laser ablation of oxide ceramics (1995)
    Springer
    Applied physics 60 (1995), S. 411-417 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.20 ; 42.60 ; 81.60.Dq
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The uv laser-ablation behavior of various oxide ceramics (Al2O3, MgO, ZrO2) has been studied using different wavelengths (248 nm, 308 nm) and pulse durations (30 ns, 500 fs). Time-resolved absorption measurements of the sample and the ablation plume during ablation were performed. Using sub-ps pulses the ablation threshold fluence is generally lower than for ns pulses; the ablation rate is higher in the whole investigated fluence range up to 20 J/cm2. The study of the morphology of the ablation structures and the results of the absorption experiments lead to the conclusion that different ablation mechanisms are involved. Using ns pulses “plasma mediated ablation” is dominating, whereas in the fs case the process is controlled by multi-photon absorption enabling microstructuring of the material.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01538343
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  • 35
    Digitale Medien
    Digitale Medien
    Dynamics of excimer laser ablation of thin tungsten films monitored by ultrafast photography (1995)
    Springer
    Applied physics 60 (1995), S. 431-436 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.60 ; 78.90
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The time course of laser light induced transport of tungsten films from a glass support is followed by ultrafast photography using delayed dye laser pulses. The photographs provide unambiguous evidence that the material transport in the 40–200 mJ/cm2 intensity domain takes place via removal of solid pieces from the film material. These results are consistent with heat flow calculations which predict the overall melting of the metal layer above 380 mJ/cm2. The series of photographs presented give detailed insight into the melting process and have revealed an unexpected in-flight phase separation of solid fracture pieces and molten droplets throughout the 200–900 mJ/cm2 domain. The faster propagating molten droplets form a condensed halo in front of the solid pieces, thereby providing an efficient shield between the processing laser light and the solid phase.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01538765
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  • 36
    Digitale Medien
    Digitale Medien
    Enhanced adhesion of metal films on PET after UV-laser treatment (1992)
    Springer
    Applied physics 55 (1992), S. 391-392 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.60 ; 61.40 ; 68.55
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The adhesion-force of thin metal films on PET foils can be significantly improved by UV excimer-laser irradiation of the polymer surface prior to metal deposition. The laser fluences required are well below the ablation threshold.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00324090
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  • 37
    Digitale Medien
    Digitale Medien
    Calculation of the dispersion of the third-order optical nonlinearity in C60 films (1995)
    Springer
    Applied physics 60 (1995), S. 49-55 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.65.An ; 36.40.+d ; 31.20.Sy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Using wave functions determined from ground-state local-density calculations, we have calculated the wave-dispersed free response of the optical nonlinear polarizabilityγ (3)(−3ω;ω,ω,ω), for the C60 molecule andχ (3)(−3ω;ω,ω,ω) i.e. Third-Harmonic Generation (THG) for films using a sum-over-states approach. The influence of screening was determined by applying an external static electric field in separate selfconsistent calculations to evaluate induced dipole moments which was used to determine the static linear and nonlinear polarizabilities. The polarizabilities calculated in the static limit were used to determine an effective screening parameter which was, in turn, used together with an RPA approach to calculate screened wave-dispersed, third-order nonlinear optical properties such asγ (3)(−3ω;ω,ω,ω) andχ (3)(−3ω;ω,ω,ω). Comparing evaluated polarizabilities with experimental values we found that the non-resonant free polarizability compares well in absolute magnitude with experimental results. Inclusion of screening results in a polarizability about two orders of magnitude below the experimental values.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01577612
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  • 38
    Digitale Medien
    Digitale Medien
    Measurement and analysis of the electric field in semiconductor lasers by continuous-wave electro-optic probing (1995)
    Springer
    Applied physics 60 (1995), S. 425-429 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 42.55.Px ; 42.60 ; 85.30
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The electric field distribution in semiconductor lasers are detected experimentally by using CWEOP (Continuous-Wave Electro-Optic Probing). The paper briefly describes the experimental results. The obtained results reflect several characteristics of the lasers such as injection current, carrier confinement, and the variation of the distribution of the electric field corresponding to different bias conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01538345
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  • 39
    Digitale Medien
    Digitale Medien
    Estimation of the capabilities of maskless micropatterning by laser-induced chemical etching (1995)
    Springer
    Applied physics 61 (1995), S. 75-80 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 81.60 ; 82.65 ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract A three-dimensional mathematical model of laser-induced chemical etching of polysilicon films in chlorine atmosphere is presented. The model takes into account both photochemical and thermochemical mechanisms. A numerical solution of a simple process model and consequences for spatial resolution limits of the mask-less laser-induced chemical etching are presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01538215
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  • 40
    Digitale Medien
    Digitale Medien
    Pairing effects in metal clusters (1992)
    Springer
    The European physical journal 22 (1992), S. 659-666 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 74.20.Fg ; 36.40.+d
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Motivated by the experimental finding of oddeven alternations in the mass spectra and ionization potentials of metal clusters, we have investigated the possibility of interpreting these results as evidence for pairing correlations among the electrons. For the present exploratory calculations, we have used a spherical BCS model which we have applied, as an example, to some Al clusters. Additional model calculations have been carried out for Na N with 34〈N〈100 in order to illustrate a possible systematics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01426369
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  • 41
    Digitale Medien
    Digitale Medien
    Production and properties of CO2 cluster anions (1992)
    Springer
    The European physical journal 24 (1992), S. 289-296 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 36.40.+d ; 35.20
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Stoichiometric and non-stoichiometric negatively charged CO2 cluster ions have been produced in a crossed neutral cluster/electron beam ion source. The abundance and stability of these ions have been studied with a double focussing sector field mass spectrometer. The observed abundance anomalies (“magic numbers”) in the mass spectra of (CO2) n − and (CO2) n O− ions correlate with corresponding small and large metastable fractions of these ions (for loss of one CO2 unit). Variation of the measured metastable fractions as a function ofn are related to corresponding changes in the monomer binding energies. In addition, we have observed for the first time (CO2) n O 2 − ions (i.e. at electron energies above 8 eV with an energy resonance at about 14 eV) and we discuss possible production mechanisms for these ions. Relative electron attachment cross sections have been determined in the energy regime O〈E≦20 eV for (CO2) n − , (CO2) n O− and (CO2) n O 2 − withn=1 to 20. The shape of the cross section function for (CO2) n O− is strongly dependent on the cluster sizen.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01425751
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  • 42
    Digitale Medien
    Digitale Medien
    Cluster size effects (1992)
    Springer
    The European physical journal 24 (1992), S. 247-275 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 36.40.+d ; 31.20.Ej ; 35.20-i ; 33.80.-b
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract In this paper we address some of the unique, novel and basic features of clusters, which involve the physical and chemical consequences of their large surface/volume ratio and the size dependence of the properties of large finite systems. Energetic, quantum, electronic, spectroscopic, and electrodynamic size effects in clusters were quantified by cluster size equations (CSEs), which describe the gradual “transition” from the large finite cluster to the infinite bulk system, with increasing the cluster size. Some progress was also accomplished in the description of the “transition” from cluster microsurfaces to macrosurfaces, which can be described in terms of surface CSEs. The analysis implies a nonuniversality principle for cluster size effects, with different physical properties being described in terms of distinct CSEs. The CSEs provide a quantitative answer to a central question in the area of cluster chemical physics: What is the minimal cluster size for which its properties become size invariant and do not differ in any significant way from those of the macroscopic sample of the same material? A unified (but not universal) description is advanced for the merging between the properties of microscopic large finite systems and those of a macroscopic bulk material.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01425749
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  • 43
    Digitale Medien
    Digitale Medien
    On the electrostatic energy of charged alkali clusters (1992)
    Springer
    The European physical journal 23 (1992), S. 269-274 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 36.40.+d
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract In the framework of the jellium model an algorithm is presented to calculate the electrostatic energy of charged metal clusters of arbitrary shape. Explicit expressions are given for some special shapes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01437404
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  • 44
    Digitale Medien
    Digitale Medien
    Molecular dynamics of 300 keV (D2O)100 clusters on Ti-D (1992)
    Springer
    The European physical journal 24 (1992), S. 385-394 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 36.40.+d ; 52.20.Hv ; 79.20.Nc
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We use the molecular dynamics code DAMSEL to predict the velocity distributions for beam and lattice atoms after bombardment of Ti-D “foils” of thickness 20.86 Å by 300 keV (D2O)100 cluster ions. From these distributions we estimate the D-D nuclear fusion yield. We find that cluster bombardment reduces the overall energy deposition of the beam in the lattice compared to that of the individual beam atoms of the same velocity. However, a small portion of lattice atoms (〈1%), and a larger percentage of beam atoms (∼30%), have energies above the maximum present in the case of bombardment by individual D or O atoms. The folding of the standard D-D fusion cross sections over the relative velocity distributions produced by beam and lattice deuterons produce a fusion yield estimate of ∼1×10−21 fusions per cluster, with the high-energy distributions of beam deuterons playing the most important role. This is nine orders of magnitude lower that the data of Beuhler et al. While transient (∼10 fs) atom densities 50% higher than that of the initial lattice are recorded in the course of the simulation, the average energy transferred per lattice atom — 23 eV — is insufficient to support any “collision spike” explanation of the observed fusion yield.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01426688
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  • 45
    Digitale Medien
    Digitale Medien
    Collision induced fragmentation of mass-selected (CO2) n + clusters (1992)
    Springer
    The European physical journal 22 (1992), S. 521-527 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 36.40.+d ; 34.90.+q
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The collisional velocity dependence of the cross sections for fragmentation of mass-selected (CO2) n + (n+2...7) clusters in collisions with Ar atoms is presented. Interesting structure can be observed in the cross sections which indicate that the collision occurs between the Ar atom and one CO2 molecule within the cluster. The results may be explained by assuming that the collision leads to either vibrational excitation of a loosely bound CO2 monomer which then leaves the cluster or excitation of the entire cluster to a dissociative state.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01426094
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  • 46
    Digitale Medien
    Digitale Medien
    Electronic structure calculations of small Al n (n=2–8) clusters (1992)
    Springer
    The European physical journal 22 (1992), S. 641-644 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 31.20.Ej ; 36.40.+d
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The electronic states of small Al n (n=2–8) clusters have been calculated with a relativistic ab-initio MO-LCAO Dirac-Fock-Slater method using numerical atomic DFS wave-functions. The excitation energies were obtained from a ground state calculation of neutral clusters, and in addition from negative clusters charged by half an electron in order to account for part of the relaxation. These energies are compared with experimental photo-electron spectra.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01426366
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  • 47
    Digitale Medien
    Digitale Medien
    Helium cluster ions RgHe x + (Rg=Ne, Ar and Kr,x≦14) formed in a drift tube cooled by liquid helium (1992)
    Springer
    The European physical journal 22 (1992), S. 645-650 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 36.40.+d ; 35.20.Wg
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Rare gas ions Ne+, Ar+ and Kr+ are injected into a drift tube which is filled with helium gas and cooled by liquid helium. Helium cluster ions RgHe x + (Rg=Ne, Ar and Kr,x≦14) are observed as products. Information regarding the stability of RgHe x + is obtained from drift field dependence of the size distribution of the clusters, and magic numbers are determined. The magic numbers arex=11 and 13 for NeHe x + andx=12 for ArHe x + and KrHe x + . NeHe x + , Ar+ and Kr+ are proposed as the core ions for NeHe 13 + , ArHe 12 + and KrHe 12 + , respectively.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01426367
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  • 48
    Digitale Medien
    Digitale Medien
    Ab-initio study of localization of an excess electron in sodium halide clusters (1992)
    Springer
    The European physical journal 23 (1992), S. 91-98 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 31.20.Di ; 31.20.Ej ; 31.90.+s ; 36.40.+d
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The equilibrium geometries of Na n F n and Na n F n−1 are optimized forn=2, 3, 4 at the SCF level. The Na n F n molecules appear as formed by Na+ and F− ions. The paper studies the localization of the excess electron in the Na n F n−1 molecules. Na n F n−1 is obtained by removing from Na n F n a fluorine atom, and the excess electron takes the place of this lacking center, and allows a weak bond between the neighbouring Na atoms. Secondary minimum geometries, for which the excess electron has no defined place, are also studied.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01436708
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  • 49
    Digitale Medien
    Digitale Medien
    Ab initio calculation of the vertical excitation energies of small helium cluster ions (1992)
    Springer
    The European physical journal 22 (1992), S. 741-745 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 31.20.Tz ; 33.20.Lg ; 36.40.+d
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Quantum chemical ab initio calculations have been performed for the vertical excitation energies and oscillator strengths of all low-lying electronically excited states of small helium cluster ions, He n + ,n=2, ..., 7. The geometrical structures of the ions were fixed at the equilibrium geometries of the respective ground states, for He 4 + and He 5 + also one alternative structure was considered. The low-lying excited states can be classified into two categories: the electronic transition can occur either within the central He 2 + or He 3 + unit or from the peripheral weakly bound He atoms to this unit. The latter transitions are very weak (f≈0.001), closely spaced, with vertical excitation energies of about 5.7 eV. The He 2 + and He 3 + units have strong transitions at 9.93 and 5.55 eV, respectively; these transitions are only slightly blue-shifted if He 2 + or He 3 + are placed as “chromophores” into the centre of a larger He n + cluster. The large difference in the vertical excitation energy of the strong transition should enable an experimental decision of the question whether the cluster ions have He 2 + or He 3 + cores.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01437257
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  • 50
    Digitale Medien
    Digitale Medien
    Effects of surface roughness on the electronic structure of metallic clusters (1992)
    Springer
    The European physical journal 24 (1992), S. 57-63 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 36.40.+d ; 31.20.Pv ; 05.40.+j
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We study the electronic level density in spherical clusters. Due to the granularity of the ionic background the surface is irregular at the microscopical level. We show that this affects the shell structure and that the level statistics display from the bottom to the top of the spectrum a transition from a poissonian behaviour to one consistent with the predictions of random matrices theory.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01436604
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  • 51
    Digitale Medien
    Digitale Medien
    Infrared molecular beam depletion spectroscopy of size-selected methanol clusters (1992)
    Springer
    The European physical journal 24 (1992), S. 277-287 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 36.40.+d ; 33.20.Ea
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Molecular beam depletion spectroscopy has been employed to study the dissociation of small methanol clusters in the spectral region between 1000 and 1100 cm−1 which covers thev 8 CO stretch (1033.5 cm−1) and thev 7 CH3 rock (1074.5 cm−1) monomer vibrations. Size selection has been achieved by dispersing the (CH3OH) n cluster beam by a secondary He beam. Aside from the recently published CH3OH dimer absorption bands at 1026.5 and 1051.6 cm−1 which are assigned to the excitation of the CO stretching vibrations in the non-equivalent subunits of the hydrogen-bonded complex, a previously unobserved band was found at 1071.3 cm−1. This absorption band is attributed to the excitation of the CH3 rocking vibration in the dimer. It appears that this transition which is very weak in the free methanol monomer receives substantial oscillator strength due to the intermolecular interaction in the complex. A splitting of this band could not be observed. The trimer and tetramer spectra feature single peaks for the CO stretching vibration being centered at 1042.2 cm−1 and 1044.0 cm−1, respectively. This observation is consistent with the cyclic structures of these species. The trimer and tetramer rocking vibrations are observed near 1060.5 cm−1 but cannot be localized exactly, due to a gap in the CO2 laser tuning range.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01425750
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  • 52
    Digitale Medien
    Digitale Medien
    Mechanisms of anion formation in O2, O2/Ar and O2/Ne clusters; the role of inelastic electron scattering (1992)
    Springer
    The European physical journal 25 (1992), S. 77-85 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 34.70.+e ; 34.80.Gs ; 36.40.+d ; 34.80.−i
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Measurements are reported on the formation of negative ions in O2, O2/Ar and O2/Ne clusters aimed at establishing the mechanisms of anion formation and the role of inelastic electron scattering by the cluster constituents on negative ion formation in clusters. In the case of pure O2 clusters the main anions we detected are of two types: O−(O2) n≧0 and (O2) n ≧1− . The yields of O−(O2) n showed maxima at 6.3, 8.0 and ∼14.0 eV and the data suggest O− as their precursor; the maxima at 8 and ∼14 eV are due to the production of O− via symmetry forbidden dissociative attachment processes in O2 at these energies which become allowed in clusters. The yields of (O2) n − showed a strong maximum at near-zero energy (∼0.5 eV) and also at 6.3, 8 and ∼14 eV. With the exception of the near-zero energy resonance, the (O2) n − anions at 6.3, 8 and ∼14 eV are attributed to nondissociative attachment of near-zero energy “secondary” electrons to O2 clusters. The slow secondary electrons result predominantly from scattering via the O 2 − negative ion states of incident electrons with energies in their respective regions. Similar results were obtained for the mixed O2/rare gas clusters except that now a feeble and distinctly structured contribution in the yields of O−(O2) n , (O2) n − (and Ar(O2) n − ) was observed at energies 〉10 eV. These anions are believed to have the lowest negative ion states of Ar*− (Ne*−) as their precursors.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01437522
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  • 53
    Digitale Medien
    Digitale Medien
    Theoretical study of the 4f photoemission spectrum in Au55 aggregates (1995)
    Springer
    The European physical journal 32 (1995), S. 337-341 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 36.40.+d ; 79.60.−i ; 36.20.Kd
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract In the photoemission process of a core level electron a satellite structure may appear due to the simultaneous excitations of valence electrons (many-electron effects). We study this phenomenon in Au55 aggregates. In this calculation we assume that the excitations can be limited to the 6s electrons which are described by means of tight-binding Hamiltonians in the initial (no core hole) and the final (hole present on a core level) states. An extension of a Anderson's formula strictly valid for the bulk is discussed and the possible use of the phase shift concept is analyzed. Our calculated satellite structure depends only on two parameters: Δ, the core hole attractive diagonal term and β, the normal transfer integral. We fix Δ/β=3 by comparison of our results to experiment performed on Au55 (P Ph3)12Cl6 compounds. The various experimental features are roughly reproduced by the calculation (number of peaks as well as their intensities and positions). Another interpretation of the experimental structure was proposed in the original experimental work. A more extensive investigation on other polyhedral metallic aggregates is necessary for allowing a choice between the two models.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01437278
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  • 54
    Digitale Medien
    Digitale Medien
    Direct temperature measurement in alkali halide cluster beam (1995)
    Springer
    The European physical journal 34 (1995), S. 135-138 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 71.50.+t ; 36.40.+d
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The temperature of a sodium fluoride cluster beam produced by laser vaporization is estimated from the rotationally-resolved laser spectroscopy of the Na2 dimer. The cluster beam is obtained by laser vaporization of a sodium rod in a mixture of helium containing a small amount (1%) of SF6. Both rotational and vibrational temperatures (respectively 170 K and 400 K) are much higher than expected from a simple theoretical model of a supersonic beam. These temperatures can be lowered to 70 K and 250 K respectively by cooling the nozzle to liquid nitrogen temperature.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01439388
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  • 55
    Digitale Medien
    Digitale Medien
    Theory for the atomic shell structure of the cluster magnetic moment and magnetoresistance of a cluster ensemble (1995)
    Springer
    The European physical journal 35 (1995), S. 273-278 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 36.40.+d ; 72.15.Gd ; 75.30.Cr
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We present a simple theory for the cluster size dependence of the average cluster magnetic moment of transition metal clusters. Assuming a local environmental dependence of the atomic magnetic moments, the cluster magnetization exhibits a magnetic shell structure, reflecting the atomic structure of the cluster. Thus, the observed oscillations of the average cluster magnet moment may serve as a fingerprint of the cluster geometry. We also discuss the giant magnetoresistance (GMR) exhibited by an ensemble of magnetic clusters embedded in a metallic matrix. It is shown that the magnetic anisotropy affects strongly the magnetization of the cluster ensemble under certain conditions. Since the GMR depends on the cluster ensemble magnetization, it can be used to determine the cluster magnetic anisotropy energy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01745530
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  • 56
    Digitale Medien
    Digitale Medien
    Photoionization studies of free sodium ammonia clusters (1992)
    Springer
    The European physical journal 22 (1992), S. 651-658 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 36.40.+d ; 33.80.Eh ; 82.40.Dm
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Free sodium ammonia clusters Na(NH3) n up ton=45 were generated in a pickup source by injecting a beam of neutral sodium atoms into the expansion zone of a piezo driven pulsed nozzle. The clusters thus formed are studied by one-photon ionisation in the region of 266 nm to 520 nm, time-of-flight mass spectrometry as well as photoelectron spectrometry. Ionisation thresholds for clusters up ton=18 and dissociation energies for the neutral Na(NH3) n up ton=6 are reported.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01426368
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  • 57
    Digitale Medien
    Digitale Medien
    Sub-picosecond laser ionization of free C60 and C70 at 248 nm (1992)
    Springer
    The European physical journal 23 (1992), S. 195-196 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 36.40.+d ; 33.80.Rv
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Delayed ionization is found to be absent for sub-picosecond laser excitation of free C60 and C70 at 248 nm. The autocorrelation trace obtained for C 60 + in a laser time-of-flight (TOF) mass spectrometer using two time-delayed and collinear 248 nm ultrashort laser pulses has a width of 1.1 ps (715 fs for sech2 pulses), in agreement with the laser pulse duration measurement in NO gas. Both above observations can be explained by direct ionization of C60 via coherent two-photon absorption by the high intensity sub-picosecond 248 nm laser excitation avoiding the channel leading to delayed ionization.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01437394
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  • 58
    Digitale Medien
    Digitale Medien
    Electron impact ionization of silver clusters Ag n ,n≦36 (1992)
    Springer
    The European physical journal 22 (1992), S. 517-520 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 36.40.+d
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Electron impact ionization of gas phase silver clusters Ag n ,n≦36 has been achieved in the threshold region. The vertical ionization potentials in this region clearly demonstrate the evidence of shell effects as well as a distinct even-odd oscillation up ton≃20. Their general size dependence is somewhat different from that of the alkali metal clusters due to the presence of thed-electrons.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01426093
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  • 59
    Digitale Medien
    Digitale Medien
    Resonant two-photon two-color photoionization (R2P2CI) spectra of aniline-Ar n clusters: Isomer strutures and solvent shifts (1992)
    Springer
    The European physical journal 22 (1992), S. 529-539 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 36.40.+d ; 35.20.Vf ; 33.80.Eh
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We present resonant two-photon two-color photoionization (R2P2CI) spectra of a series of Aniline-Ar n complexes (n=1−6). An apparently anomalous blue shifted spectra for An-Ar3 is explained by a modified spectral shift additivity rule which assigns different shifts to different relative positions of the Ar with respect to aniline. Evidence is presented for the existence of several isomers of clusters withn≧2. It is shown that, by changing the nucleation conditions, it is possible to control the relative populations of the various isomers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01426095
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  • 60
    Digitale Medien
    Digitale Medien
    Distribution of interatomic distances in large metallic clusters (1992)
    Springer
    The European physical journal 22 (1992), S. 541-545 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 36.40.+d ; 61.50.Cj
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Spherically averaged pseudopotential (SAPS) calculations have been done for Mg n clusters, withn up to 250 within the framework of density functional theory. The electronic structure is computed resorting to the Thomas-Fermi-Dirac-Weizsäcker (TFDW) approximation for the kinetic energy. The equilibrium geometries have been obtained by minimizing the total cluster energy with respect to the atomic positions using the steepest-descent method. The ground state geometries obtained in this way are formed by spherical atomic shells, the number of them increasing with cluster size, up to a number of four for the biggest sizes considered here. An analysis of the distribution of the interatomic distances shows that the more internal is the shell, the more contracted are the interatomic distances. This effect diminishes progressively with increasing cluster size. For the purpose of comparison, similar calculations have been done with Cs n clusters in the same size range, allowing us to reproduce previous results obtained using a more elaborated density functional technique (Kohn-Sham method). The inhomogeneous contraction of interatomic distances then appears as a general fact for simple metallic clusters and not only for alkaline ones.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01426096
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  • 61
    Digitale Medien
    Digitale Medien
    Simulation of cluster impact fusion (1992)
    Springer
    The European physical journal 22 (1992), S. 547-551 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 36.40.+d ; 79.20.Rf
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We report molecular dynamics simulations of the impact of TiD clusters on TiD targets. In each cluster collision the total fusion probability seems to be due to a single deuterium deuterium collision. The kinetic energies of incident deuterium atoms gradually level off around the initial cluster energy, but do not reach the high energy tail of a corresponding Maxwell-Boltzmann distribution. Neither any other support for a thermonuclear fusion mechanism was observed. On the contrary, our simulations imply that the enhanced fusion rate is rather due to channeled many atom collision cascade type mechanism.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01426097
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  • 62
    Digitale Medien
    Digitale Medien
    Ionic core effects on the mie resonance in lithium clusters (1995)
    Springer
    The European physical journal 32 (1995), S. 329-336 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 36.40.+d ; 78.20.−e
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We investigate the effects of the atomic cores on the Mie resonance in lithium metal clusters, perturbing a jellium Hamiltonian with zero-range pseudopotentials. The resonance is red-shifted with respect to the classical formula by core effects, most important of which is the increased effective mass due to the core potentials. Much of the large shift seen in lithium clusters is thereby explained if the strength of the pseudopotentials is taken from band structure calculations. However, such pseudopotentials cause the resonance to be greatly broadened, contrary to observation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01437277
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  • 63
    Digitale Medien
    Digitale Medien
    Mass distribution of cluster ions produced from laser ablation of metal-composite-oxides Y-M-Cu-O (M=Ba, Sr, Ca, Mg) (1995)
    Springer
    The European physical journal 34 (1995), S. 257-261 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 36.40.+d ; 35.20.Wg ; 34.10.+x
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Laser ablation of YMCuO metal-composite-oxides (M=Ba, Sr, Ca, Mg) in high vacuum produced cluster ions with various sizes and compositions. Mass spectra of the cluster ions were recorded by a home-built time-of-flight (TOF) mass spectrometer and the mass distributions were analyzed by a statistical model. For YBa2Cu3O7−x (YBCO) high-Tc superconducting samples, six series of cluster ions were observed. Replacement of barium in the metal-composite-oxide sample with other alkaline earth metal, such as strontium, calcium, or magnesium, not only removed the superconductivity, but also changed the compositions and distributions of the laser generated cluster ions. For instance, copper was only found in the compositions of cluster ions generated from YBCO sample. From comparison of the experimental results, interactions among components of the metal-composite-oxides and the function of alkaline earth metal in superconducting material were discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01437571
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