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891.
The interaction between the rotational degrees of freedom of a diatomic impurity molecule and phonon excitations of a two-dimensional atomic matrix commensurate to the substrate is investigated theoretically. It is shown that the translational-rotational interaction leads to renormalization of the crystal field constants and a change in the form of the operator for the rotational kinetic energy as compared to the corresponding expression for a free rotator. The contribution from the rotational degrees of freedom of impurities to the low-temperature heat capacity of a diluted solution of diatomic molecules in the two-dimensional atomic matrix is calculated. The possibility of experimentally observing the predicted effects is discussed. 相似文献
892.
893.
894.
The propagation and absorption of high-frequency sound in the isotropic phase of cholesteryl miristate is studied in a wide frequency range using the data of both Brillouin spectroscopy and acoustooptic measurements. The parameters of the relaxation process associated with the volume viscosity relaxation are calculated using the experimental data on the velocity and absorption of sound. 相似文献
895.
The feasibility of an effective high-luminance light source based on an open discharge is considered. Experimental data for
the light characteristics of different cathodoluminescent screens are presented. Phosphor coatings are excited by an electron
beam initiated by a planar cathode-grid injector in an inert gas atmosphere. The feasibility of maintaining an open discharge
using continuous or pulsed-periodic excitation of the gas medium in the light emitter is discussed. The use of the specular
method to excite the phosphor coating of the screen makes it possible to achieve a higher luminance and a higher luminous
efficacy in comparison with these characteristics for cathodophosphors. The design of the cathode-grid unit allows for a large
surface area of the electron injector, making it promising for wide-aperture light sources. 相似文献
896.
Formulas for calculating the spectral characteristics of waveguide arrays, which are incorporated into waveguide spectrum analyzers based on planar waveguides, channel waveguides, and fiber optical waveguides, are derived taking into account the contribution of both the waveguide dispersion and the material dispersion to the dispersion factor. These formulas are used to study the dependence of the dispersion factor on the waveguide-system parameters for specific models of waveguide arrays. It is shown that consideration of contributions of the waveguide dispersion and material dispersion can affect profoundly the spectral characteristics of waveguide arrays. 相似文献
897.
Picosecond stimulated Raman scattering in crystals 总被引:1,自引:0,他引:1
T. T. Basiev P. G. Zverev A. Ya. Karasik V. V. Osiko A. A. Sobol’ D. S. Chunaev 《Journal of Experimental and Theoretical Physics》2004,99(5):934-941
The comparative values of the peak and integral cross sections of spontaneous Raman scattering and the optical dephasing time of molecular vibrations were determined for several oxide crystals by spontaneous Raman spectroscopy. The spectral, time, and energy parameters of stimulated Raman scattering (SRS) were measured for ten crystals using picosecond YLF: Nd laser pumping with a radiation wavelength of 1047 nm. An analysis of the experimental dependence of the threshold energy of pumping SRS on the integral and peak cross sections of spontaneous Raman scattering showed that the SRS gain increment explicitly depended on the integral cross section and was independent of the peak cross section of spontaneous Raman scattering as the ratio between the pumping pulse width (11 ps) and the time of optical dephasing of molecular vibrations changed from 0.42 to 9.3. The gain coefficients of steady-state stimulated Raman scattering under threshold stimulated Raman scattering conditions were determined for all the crystals studied on the basis of the measured threshold SRS pumping energies, the duration and width of the spectrum of pulses, the nonlinear interaction length, the intensity of pumping, and the theoretical dependences that relate the steady-state and transient SRS gain increments. The steady-state SRS gain coefficients obtained in this work fitted well a linear dependence on the peak cross sections of spontaneous Raman scattering, which substantiated the correctness of our analysis and measurements. 相似文献
898.
A. N. Aleev N. S. Amaglobeli V. P. Balandin O. V. Bulekov I. M. Geshkov T. S. Grigalashvili E. A. Goudzovski D. K. Guriev D. D. Emelianov S. V. Eremin A. I. Zinchenko Z. M. Ivanchenko I. M. Ivanchenko M. N. Kapishin A. A. Loktionov V. D. Kekelidze Z. I. Kozhenkova V. V. Korenkov I. G. Kosarev N. A. Kuzmin A. L. Ljubimov D. T. Madigozhin V. G. Maznyj A. S. Mestvirishvili N. A. Molokanova A. N. Morozov R. E. Pismenyj V. D. Poze I. A. Polenkevich A. K. Ponosov T. Ponta Yu. K. Potrebenikov F. M. Sergeev L. A. Slepets V. N. Spaskov 《Physics of Atomic Nuclei》2004,67(8):1513-1522
The features of the associated production of φ mesons with Λ0 hyperons in neutron-carbon interactions were investigated. The experiment was performed with the aid of the EXCHARM spectrometer at the Serpukhov accelerator in a neutron beam of energy in the interval 20–70 GeV. The differential cross section for inclusive associated φΛ0 production was measured. 相似文献
899.
D. T. Le C. P. Morath H. E. Norton D. A. Cardimona S. Raghavan P. Rotella S. A. Stintz B. Fuchs S. Krishna 《Infrared Physics & Technology》2003,44(5-6):517-526
In this paper we report studies on normal incidence, InAs/In0.15Ga0.85As quantum dot infrared photodetectors (QDIPs) in the dots-in-a-well (DWELL) configuration. Three QDIP structures with similar dot and well dimensions were grown and devices were fabricated from each wafer. Of the three devices studied, the first served as the control, the second was grown with an additional 400 Å AlGaAs blocking layer, and the third was grown on a GaAs n+ substrate with the intention of testing a single pass geometry. Spectral measurements on all three devices show one main peak in the long-wave IR (≈8 μm). The absorption was attributed to the bound-to-bound transition between the ground state of the InAs quantum dot and the ground state of the In0.15Ga0.85As well. Calibrated peak responsivity and peak detectivity measurements were performed on each device at 40, 60, and 80 K. For the same temperatures, frequency response measurements from 20 Hz to 4 kHz at a bias of Vb=−1 V were also performed. The addition of the blocking layer was shown to slightly enhance responsivity, which peaked at 2.4 A/W at 77 K, Vb=−1 V and responsivity was observed to be significantly reduced in the single pass (n+ substrate) sample. The rolloff of the frequency response was observed to be heavily dependent on temperature, bias, and irradiance. The results from the characterization of each sample are reported and discussed. 相似文献
900.
V. K. Voronkova R. T. Galeev S. Shova G. Novitchi C. I. Turta A. Caneschi D. Gatteschi J. Lipkowski Yu. A. Simonov 《Applied magnetic resonance》2003,25(2):227-247
New compounds, [Cu3Ln2(ClCH2COO)12(H2O)8]·2H2O with Ln = Nd3+ (I), Sm3+ (II), Pr3+ (III), built up of pentanuclear clusters were synthesized and studied by means of X-ray analysis and electron paramagnetic
resonance (EPR). X-ray data show that all compounds are isostructural and the pentanuclear clusteres may be considered as
a linear system with alternating Cu(II) and Ln(III) ions: Cu(2)-L1-Ln-L2-Cu(1)-L2-Ln-L2-Cu(2) with L1 and L2 being bridging fragments and Cu(1) and Cu(2) being structurally nonequivalent copper complexes. EPR studies demonstrate that
in the temperature range of 100–293 K the signals due to only one type of the copper complexes are observed in the spectra
of I–III. AtT<100 K the spectral temperature dependence is nontrivial. AtT<30 K new signals are detected in the spectra of I and II. The temperature dependence of the EPR spectra is interpreted under
the assumption that the parameter of the exchange interaction Cu(2)-Ln considerably exceeds the parameter of the interaction
Cu(1)-Ln. EPR spectra are calculated for the fragments of five paramagnetic centers in the frames of the model taking into
account the nonequivalence of two copper complexes, short longitudinal and transverse paramagnetic relaxation times of the
rare-earth ions at room temperature and the change of the relaxation rates when the temperature decreases. The results of
the calculations show that it is possible to obtain information about the interactions in the system on the basis of the analysis
of the temperature dependence of the EPR spectra of the central copper complex. The parameter of the isotropic part of the
exchange interaction between copper and neodymium ions (for the interaction Cu(2)-Nd) is estimated as about 15 cm−1. A considerable rearrangement of the spin states when the temperature changes is found for all complexes. 相似文献