Rate coefficients of XeO(1S) at various vibrational levels (v = 0, 1 and 2) were observed by measuring absolute intensities of the spectrum in the low-pressure d.c. glow of an Xe-O2 mixture discharge. The association coefficients at the various levels are Ka0 = 2.4×10-34 cm6 at v = 0, Ka1 = 1.1 × 10-34 cm6 atv = 1, and Ka2 = 9.1 × 10-35 cm6 at v = 2. The transition probability from XeO(1S)0 to is estimated to be A0 = 1.3 × 105 sec-1. 相似文献
ESR study of VO2+ doped trisodium citrate pentahydrate is undertaken at room temperature. The observed spectra are correlated with the available crystal structure data and are fitted to a spin Hamiltonian of orthorhombic symmetry with gx = 1.998 ± 0.001, gy = 1.992 ± 0.001, gz = 1.934 ± 0.001, Ax = (70.0 ± 1) × 10-4cm-1, Ay = (66.6 ± 1) × 10-4cm-1 and Az = (175.4 ± 1) × 10-4cm-1. The covalency and Fermi contact parameters are evaluated and compared with those of VO2+ in other lattices. 相似文献
Brillouin scattering experiments in the layer-type semiconductors GaSe and GaS by the pure-transverse phonon domains have been carried out at room temperature. Weak resonant enhancement and cancellation have been found for both materials in the region of transparency. The non-diagonal elastic constants C12 have also been determined to be 3.77 × 1011 dyn cm?2 (GaSe) and 5.35 × 1011 dyn cm?2 (GaS) by measuring the sound velocities of the phonon domains. 相似文献
In conditions of inversion of spin-level populations at T = 1.7° K the resonant stationary coherent phonon emission has been revealed in ruby at frequency ν = 9.12 GHz. The intensity of emission is IS ≈ 10?6 W·cm?2. The frequency spectrum consists of very narrow lines generated simultaneously on several modes of hypersonic ruby cavity. Monochromatism of emission in each line is Δν/ν ? 2 × 10?6. The spectrum nature permits to suppose the levelwidth of elementary spin excitation to be Δνs < 3 × 105 Hz, i.e. at least 2–3 orders it is narrower than the inhomogeneously broadened resonant line in ruby. The lifetime of resonant phonons in ruby was defined: τ = 7 × 10?6 sec. 相似文献
The v = 0?0 quadrupole spectrum of H2 has been recorded using a 0.005-cm?1 resolution Fourier transform spectrometer. The rotational lines S(1) through S(5) are observable in the spectra, in the region 587 to 1447 cm?1. The spectral position for S(0) was also obtained from its v = 1-0 ground-state combination difference. The high accuracy of the H2 measurements has permitted a determination of four rotational constants. These are (in cm?1) B0 = 59.33455(6); D0 = 0.045682(4); H0 = 4.854(12) × 10?5; L0 = ?5.41(12) × 10?8. The hydrogen line positions will facilitate studies of structure and dynamics in astrophysical objects exhibiting infrared H2 spectra. The absolute accuracy of frequency calibration over wide spectral ranges was verified using 10-μm CO2 and 3.39-μm CH4 laser frequencies. Standard frequencies for 5-μm CO were found to be high by 12 MHz (3.9 × 10?4 cm?1). 相似文献
We report stimulated Raman investigations of N2 Q-branch transitions in view to measure the self-density frequency shift. These measurements performed at 295 K over the density range 0.02-0.8 Amagat lead to a mean shift value equal to -5.5×10-3 cm-1/Amagat. Moreover, our data extrapolated at zero density allowed new refinements of the N2 molecular constants: v0=2329.91165 (17) cm-1, B1–B0=-0.0173714 (22) cm-1 and D1–D0=(7.6±5.0)×10-9 cm-1. 相似文献
Propagation of nonequilibrium acoustic phonons in samples of high-purity CdTe (impurity content ~1016 cm?3) was studied using the heat pulse technique under pulsed photoexcitation. An analysis of nonequilibrium phonon propagation made by comparing the experimental response with Monte Carlo calculations assuming samples to be without twins provided an estimate for the spontaneous anharmonic phonon decay constant AL=2×10?52 s?1 Hz?5. The probability of free phonon transit through a twin boundary in a sample with twin structure was estimated as AC=0.96. 相似文献
Time-resolved measurements, together with spectroscopic study with a grating monochromator, are made on far-infrared stimulated emission from p-Ge in crossed electric and magnetic fields. Gain saturation is confirmed, for the first time, to occur to establish laser oscillation. Small-signal gain per unit length deduced from the time constant of light amplification is 7.4 × 10-3 cm-1 and 2.7 × 10-2 cm-2, respectively, for samples with NA − ND ≅ 4.5 × 1013cm−3 and 1.7 × 1014 cm-3. Output power detected at distance 28 cm from the sample is of order 1–10 W, but higher power over 100W is suggested for the total output from the sample. 相似文献
Confocal micro-Raman spectroscopy was preformed to investigate the structural damage of SiC neutron irradiated with the fluences of 1.72×1019 and 1.67×1020 n/cm2. In addition to characteristic peaks, several additional signals related to Si–Si, Si–C, and C–C vibration modes were monitored. The vibration mode associated with CSiV C complexes was identified to be the unambiguous peak at 575 cm?1 which appears initially in the sample post-irradiation annealed at 800 °C. The defect-induced phonon confinement effect results in an asymmetric broadening with a low-frequency tail of the optical phonon peaks. The sigmoidal thermal recovery behavior of the optical phonon frequencies indicates that the reduction of FLO0/6–FTO2/6 splitting originates mainly from the isolated vacancies and interstitials. 相似文献
Laser-induced cesium plasmas were diagnosed by emission spectroscopy, yielding electron densities in the range Ne = 1016?5 × 1017 cm-3 and electron temperatures in the range Te = 0.2-1 eV. The experimental lineshapes for Te = 0.5 eV were found to be in good agreement with theory. For the more strongly coupled plasmas at Ne = 1-2 × 1016 cm-3 and Te = 0.2 eV, however, the Cs I 5d-5? lineshape was more asymmetric than predicted. 相似文献
The superatomic structure of synthetic quartz single crystals with dislocation densities ρ = 54 and 570 cm?2 was studied in the initial state and after irradiation with fast neutrons with energies En > 0.1 MeV in a WWRM reactor (St. Petersburg Nuclear Physics Institute) in the fluence range F = 0.2 × 1017?5.0 × 1018 neutrons/cm2. Weak irradiation with F = 0.2 × 1017 neutrons/cm2 causes only slight structural changes, whereas appreciable generation of defects with radii of gyration rg ~ 1–2 nm and RG ~ 40–50 nm occurs at F = 7.7 × 1017?5.0 × 1018 neutrons/cm2. As the fluence increases further, the number and volume fraction of point defects, as well as extended (channels ~2 nm in radius) and globular (amorphous phase nuclei) defects, increase. 相似文献
The enhancement of the cross section for Raman scattering has been measured near resonance with the 1S yellow exciton in Cu2O . The shape of the enhancement is shown to be Lorentzian to beyond 10 halfwidths from the peak. From the temperature dependence of the width of the enhancement profile, we extract separately the rates for exciton- acoustic phonon scattering, γsc(T), and for non-radiative decay, γnr, of this exciton state. We find γnr = 2.4 × 1010sec-1 and γsc(T=5.4K) = 0.85 × 1010sec-1. 相似文献
ESR spectra of VO2+ doped tripotassium citrate are recorded at room temperature. The observed spectra are fitted to a spin Hamiltonian of orthorhombic symmetry with gx = 2.001 ± 0.001, gy = 1.997 ± 0.001, gz = 1.945 ± 0.001, Ax = (49.0 ± 1) × 10−4 cm−1, Ay = (66.8 ± 1) × 10−4 cm−1 and Az = (168.4 ± 1) × 10−4 cm−1. The covalency and Fermi contact terms are evaluated and compared with those of other lattices. 相似文献
Absolute intensities of the vibration-rotation lines of the CO2 401II←000 band 7734 cm-1 are measured under high-resolution, low-pressure conditions by use of a White-type 25-m base-path, absorption cell together with a 5-m Czerny-Turner spectrometer. The total band intensity SB, the purely vibrational transition moment , and the vibration-rotation interaction constant ζ are calculated from the intensity measurements. The values obtained for these parameters are SB(401II) = (7.06±0.07) × 10-5 cm-2 atm-1293°K, = (3.08±0.03)×10-5 debye, and ζ = (2.5±0.5)×10-4. The intensity of the associated “hot band” 411II←010 is also determined and found to be SB(411II←010) = (0.53±0.02)×10-5 cm-2 atm-1293°K. 相似文献
The dynamics of intersubband relaxation in GaAs quantum wells and the role of hot carriers and the phonon distributions have been investigated using two different optical techniques with femtosecond resolution: 1) time-resolved photoluminescence and 2) pump and probe experiments. The (2→1) intersubband relaxation times have been measured as functions of well widths (100Å < Lwell < 220Å), under different experimental conditions (15K < Tlattice < 300K, and 1×1010 cm-2 < excitation densities < 1×1012 cm-2). The electron intersubband relaxation time is deduced from the decay time of the n=2 well luminescence (or differential transmission) intensity. For thin wells (<150Å), a fast intersubband (2→1) relaxation time ≤ 3 ps has been measured. For thicker wells, the measured decay times are found to be critically dependent on the excitation conditions (vary from 5 ps to 40 ps). The well width dependence of the intersubband relaxation time does not show the strong dependence (2 orders of magnitude) predicted theoretically for electron-LO phonon scattering. Our results show that the hot phonon populations and the slow carrier cooling rate limit the observation of subpicosecond relaxation time. For thick well widths, our results also suggest that hot carriers effects play an important role in the intersubband relaxation mechanisms. 相似文献
We have measured the propagation velocities of bulk acoustic waves in the simple cubic transition-metal oxide ReO3 by ultrasonic pulse propagation. The elastic stiffness constants at 300 K are: C11 = (47.9 ± 1.4) × 1011 dyne/cm2; C44 = (6.1 ± 0.2) × 1011 dyne/cm2; C12 = (?0.7 ± 2.8) × 1011 dyne/cm2. These elastic constants indicate a crystal with highly anisotropic shear propagation. The Debye temperature of the compound from these measurements is 528 K. This value is somewhat higher than previous results from specific heat and resistivity determinations. 相似文献
The adsorption and desorption of nitrogen on a platinum filament have been studied by thermal desorption techniques. Nitrogen adsorption becomes significant only after any carbon contamination is removed from the surface by heating the platinum filament in oxygen, and after the CO content in the background gas is reduced substantially. At room temperature nitrogen populates an atomic tightly bound β-state, E≠ = 19 kcal mole?1. The saturation coverage of the (3-state is 4.5 × 1014 atoms cm?2. Formation of the (β-state is a zero order process in the pressure range studied. At 90 K two additional α1- and α2-desorption peaks are observed. The activation energy for desorption for the α2-state is 7.4 kcal mole?1 at low coverage decreasing to 3 kcal mole?1 at saturation of this state, 6 × 10 molecules cm?2. The maximum total coverage in the α-states was 1.2 × 1015 molecules cm?2. A replacement process between the β- and α-states has been observed where each atom in the (β-state excludes two molecules from the α-state. 相似文献
We have used the technique of chemical vapour transport to prepare needle shaped single crystal of ZrS3. Results of the measurements of d.c. resistivity. Hall coefficient and thermoelectric power of the temperature range 100–500 K are reported. All the samples exhibited semiconducting behaviour with a room temperature resistivity of about 15 Ω-cm and an activation energy of 0.20±0.02 eV. Room temperature thermoelectric power is -850 μVK?1 and the dominant carriers are electrons. The thermoelectric power varies as (1/T), a behaviour associated with a typical semiconductor. Mobility at low temperatures is limited by ionized impurity scattering and is given by μ1 = 6.5 × 10?2T3/2 cm2V7-1 sec?1. At high temperatures, phonon scattering is dominant and the mobility is given by μ2 = 1.35 × 10+5T?32 cm2V?1 sec?1. 相似文献
The phonon-defect interaction in KC1:CN? has been studied in the 16 GHz frequency range using the Brillouin scattering technique. Brillouin spectra of KC1:CN? at 4.2 K show a defect induced phonon velocity renormalization. The measurements are consistent with a 〈111〉 oriented CN? dipole in KC1 with a tunneling level of T2g symmetry at 2.6 cm?1 and a coupling constant of 1.5 × 10?21 cm3. 相似文献