Resonant Raman scattering in GaP in the E0 − E0 + Δ0 region

Resonant enhancement of the cross section for Raman scattering by TO phonons in GaP at the E₀ and E₀ + Δ₀ gaps has been observed using a continuously tunable pulsed dye laser pumped by a nitrogen laser and a gated photon counting system. The resonance at the spin-orbit split E₀ + Δ₀ gap is much weaker than that at E₀ and has not been observed previously in first-order Raman scattering. The results are in good agreement with theoretical predictions.     

对氯氟苯S0, S1和D0态的实验与理论研究

本文采用共振增强多光子电离和慢电子速度成像技术研究了对氯氟苯(p-ClFPh)在中性第一激发态和阳离子基态下的几何结构和振动频率. 给出了对氯氟苯S₀态的红外光谱和S₁←S₀跃迁的吸收光谱. 基于单色、双色共振增强双光子电离技术，得到了对氯氟苯的跃迁激发能是36302±4 cm^-1. 通过阈值电离测量，外推得到对氯氟苯的绝热电离能为72937±8 cm^-1. 此外，通过Franck-Condon模拟，确定了S₁和D₀态的主要振动模式，并分析了对氯氟苯分子S₀&S₁和S₁&D₀跃迁过程中的Duschinsky振动模式混合效应.     

The break-up reaction p0 + d → p1 + p2+ n at E0 = 16 MeV

The break-up reaction p₀ + d → p₁ + p₂ + n has been studied at E₀ = 16 MeV in kinematically complete p₁-p₂ coincidence experiments with special regard to n-p final-state interactions (f.s.i.) and p₁-p₂ quasifree scattering (q.f.s.). The absolute differential cross section has been measured for n-p f.s.i. c.m. production angles from 60° to 140° and for four pairs of angles with strong contributions due to q.f.s. Calculations with separable nucleon-nucleon potentials based on the Faddeev equations are in good agreement with the data obtained. In general, the shape of the experimental differential cross section is well reproduced. Discrepancies of up to 30 % in the worst cases arise between the absolute values of the theoretical predictions and the experimental data.     

Scalar mesons σ and α0 in the decay η′ → ηπ0π0

The matrix element for the decay η′ → ηπ ⁰ π ⁰ is studied with allowance for the scalar mesons σ and α ₀. Good agreement with experimental data is obtained.     

Determination of hadronic partial widths for scalar-isoscalar resonances f0(980), f0(1300), f0(1500), f0(1750) and the broad state f0(1530 ?250+90 )

Recently [see V.V. Anisovich et al., Yad. Fiz. 63, 1489 (2000)], the K-matrix solutions for the wave IJ ^PC=00⁺⁺ were obtained in the mass region 450–1900 MeV, where four resonances f ₀(980), f ₀(1300), f ₀(1500), f ₀(1750) and the broad state f ₀(1530 ₋₂₅₀ ⁺⁹⁰ ) are located. Based on these solutions, partial widths are determined for scalar-isoscalar states decaying into the channels ππ, KK ηη, ηη′, ππππ and corresponding decay couplings. From Yadernaya Fizika, Vol. 65, No. 8, 2002, pp. 1583–1590. Original English Text Copyright ? 2002 by Anisovich, Nikonov, Sarantsev. This article was submitted by the authors in English.     

Sub-kilohertz optical linewidths of the 7F0 ↔ 5D0 transition in Y2O3:Eu3+

Homogeneous optical linewidths as small as 760 Hz (fwhm) have been observed in Y₂O₃:Eu³⁺ using delayed heterodyne photon echoes. Hyperfine and lifetime contributions to dephasing are estimated to contribute ? 300 Hz to this width, and the remainder is attributed to quasi-resonant energy transfer.     

Molecular dynamics simulation of the (0 0 0 1) α-Al2O3 and α-Cr2O3 surfaces

A simple, rigid pair-potential model is applied to investigate the dynamics of the (0 0 0 1) α-Al₂O₃ and α-Cr₂O₃ surfaces using the molecular dynamics technique. The simulations employ a two-stage equilibration process: in the first stage the simulation-cell size is determined via the constant-stress ensemble, and in the second stage the equilibration of the size-corrected simulation cell is continued in the canonical ensemble. The thermal expansion coefficients of bulk alumina and chromia are evaluated as a function of temperature. Furthermore, the surface relaxation and mean-square displacement of the atoms versus depth into the slab are calculated, and their behaviour in the surface region analysed in detail. The calculations show that even moderate temperatures (∼400 °C) give rise to displacements of the atoms at the surface which are similar to the lattice mismatch between α-alumina and chromia. This will help in the initial nucleation stage during thin film growth, and thus facilitate the deposition of α-Al₂O₃ on (0 0 0 1) α-Cr₂O₃ templates.     

Influence of substrate temperature in BiFeO3-CoFe2O4 nanocomposites deposited on SrTiO3 (0 0 1)

BiFeO₃-CoFe₂O₄ epitaxial nanocomposites have been deposited on SrTiO₃ (0 0 1) substrates by pulsed laser deposition. We present here a study of the influence of the deposition temperature (T_S), in the 550-800 °C range, on the film composition, morphology and microstructure. Electron-probe microanalysis shows strong reduction of the Bi content in the films when increasing T_S. Films prepared at T_S=750 °C and above are virtually Bi-free. X-ray diffraction (XRD) data show that, due to the volatility of Bi, there is a progressive reduction in the amount of BiFeO₃. The deposition temperature and the concomitant presence of Fe_xO_y spurious phases in the nanocomposites grown at high temperature promote radical changes in film morphology and magnetization. It thus follows that a temperature range suitable for controlled modification of nanocomposites morphology would be extremely narrow.     

Effect of aggregation on the radiative (T1 → S0) and nonradiative (T1⇝S0 and S1⇝T1) transitions in xanthene dyes

The measurement of triplet decay time (τ_p) and the relative yields of phosphorescence to fluorescence (φ_p/φ_f) have been made in solutions of xanthene dyes. The value of φ_p/φ_f increases while that of τ_p decreases as the concentration of the solution is increased. The rate constants k_p, k_qp and k_is have been estimated. It is found that the values of k_qp and k_is increase while that of k_p remains substantially constant for the entire range of concentration. The deuterium solvent effect is observed in τ_p and φ_p.