Rate coefficient and transition probability of XeO

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 K_a0 = 2.4×10^-34 cm⁶ at v = 0, K_a1 = 1.1 × 10^-34 cm⁶ atv = 1, and K_a2 = 9.1 × 10^-35 cm⁶ at v = 2. The transition probability from XeO(¹S)₀ to $\text{XeO(}{}^1\text{D)u}$ is estimated to be A₀ = 1.3 × 10⁵ sec^-1.     

ESR study of vanadyl ion in trisodium citrate pentahydrate

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 g_x = 1.998 ± 0.001, g_y = 1.992 ± 0.001, g_z = 1.934 ± 0.001, A_x = (70.0 ± 1) × 10^-4cm^-1, A_y = (66.6 ± 1) × 10^-4cm^-1 and A_z = (175.4 ± 1) × 10^-4cm^-1. The covalency and Fermi contact parameters are evaluated and compared with those of VO²⁺ in other lattices.     

Brillouin scattering by pure-transverse phonons in GaSe and GaS

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.     

Generation of coherent phonons in ruby

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 I_S ≈ 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 Δν_s < 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.     

α-Al2O3单晶中Fe3+离子的电子顺磁共振

本文对α-Al₂O₃单晶体中Fe³⁺离子在室温下,X波段进行了电子顺磁共振研究,发现Fe³⁺离子实际上占据四种磁性不等价晶位。在同一氧离子层间的两种晶位上的Fe³⁺离子具有相同的自旋哈密顿参量,而不同氧离子层间的晶位上的Fe³⁺离子具有不同的自旋哈密顿参量,两种自旋哈密顿参量为:(1)g_‖=2.001,g_⊥=2.003,D=1679 关键词：     

The ground state of molecular hydrogen

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).     

Self-density frequency shift measurements of Raman N2 Q-branch transitions

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.     

Nonequilibrium phonon propagation in high-purity CdTe

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 A_L=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 A_C=0.96.     

Far-infrared laser oscillation in p-Ge

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 N_A − N_D ≅ 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.     

Raman scattering of neutron irradiated 6H-SiC

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 C_SiV _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 FLO_0/6–FTO_2/6 splitting originates mainly from the isolated vacancies and interstitials.     

Anomalous Cs I 5d-5⨍ lineshape in a non-debye plasma

Laser-induced cesium plasmas were diagnosed by emission spectroscopy, yielding electron densities in the range N_e = 10¹⁶?5 × 10¹⁷ cm^-3 and electron temperatures in the range T_e = 0.2-1 eV. The experimental lineshapes for T_e = 0.5 eV were found to be in good agreement with theory. For the more strongly coupled plasmas at N_e = 1-2 × 10¹⁶ cm^-3 and T_e = 0.2 eV, however, the Cs I 5d-5? lineshape was more asymmetric than predicted.     

Small-angle neutron scattering study of radiation defects in synthetic quartz

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 E _n > 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 r _g ～ 1–2 nm and R _G ～ 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.     

Lineshape studies of the 1s yellow exciton in Cu2O by resonance Raman scattering

The enhancement of the cross section for Raman scattering has been measured near resonance with the 1S yellow exciton in Cu₂O $\text{(}\text{v}{}_{\mathrm{1SY}}\text{? 16,399 cm}{}^{-1}\text{)}$. 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, γ_sc(T), and for non-radiative decay, γ_nr, of this exciton state. We find γ_nr = 2.4 × 10¹⁰sec^-1 and γ_sc(T=5.4K) = 0.85 × 10¹⁰sec^-1.     

ESR study of vanadyl ion in tripotassium citrate

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 g_x = 2.001 ± 0.001, g_y = 1.997 ± 0.001, g_z = 1.945 ± 0.001, A_x = (49.0 ± 1) × 10⁻⁴ cm⁻¹, A_y = (66.8 ± 1) × 10⁻⁴ cm⁻¹ and A_z = (168.4 ± 1) × 10⁻⁴ cm⁻¹. The covalency and Fermi contact terms are evaluated and compared with those of other lattices.     

The absorption spectrum of CO2 around 7740 cm-1

Absolute intensities of the vibration-rotation lines of the CO₂ 401_II←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 S_B, 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 S_B(401_II) = (7.06±0.07) × 10^-5 cm^-2 atm^-1_293°K,

= (3.08±0.03)×10^-5 debye, and ζ = (2.5±0.5)×10^-4. The intensity of the associated “hot band” 411_II←010 is also determined and found to be S_B(411_II←010) = (0.53±0.02)×10^-5 cm^-2 atm^-1_293°K.     

Ultrafast dynamics of intersubband relaxation in GaAs quantum wells: hot carrier and phonon populations effects

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 < L_well < 220Å), under different experimental conditions (15K < T_lattice < 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.     

Stiffness matrix and debye temperature of ReO3 from ultrasonic measurements

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.     

Adsorption of nitrogen on platinum

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.     

Electrical transport measurements in a quasi-onedimensional semiconductor ZrS3

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^?2T^3/2 cm²V^7-1 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.     

Brillouin scattering observation of phonon renormalization in KC1:CN−

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 T_2g symmetry at 2.6 cm^?1 and a coupling constant of 1.5 × 10^?21 cm³.