用多步激发技术测定锶的(5p3/2ns)1及(5p3/2nd)3自电离谱

用分步激发方法及偏振光技术,测定了锶的(5p_3/2ns)₁(n=13-21)及(5p_3/2 nd)₃(n=13-24)各自电离谱,在低于5p_1/2电离限的(5p_3/2ns)₁态的实电子激发谱中,出现对应于(5p_1/2ns)₁及(5p_1/2nd)₁的畸变峰,畸变峰也出现于(5p_3/2nd)₃的实电子激发谱中。这说明(5p_jns)(5p_jnd)自电离系列间存在相互作用。 关键词：     

Sr(5p1/2nd)3自电离谱的测定

用分步激发技术测得了Sr(5p_1/2nd)₃系列(n=11—24)自电离能级的位置及其有效量子数ν_1/2。对其与(5p_3/2nd)₃,系列间可能存在的组态相互作用,进行了初步探讨。 关键词：     

Derp 3/2-Analogzustand in51V

In an investigation ofT=7/2 analogue states in⁵¹V the⁵⁰Ti(p, γ) excitation curve has been measured for proton bombarding energies 1280–1480 keV and 2340–2660 keV. From the (p, γ) resonances 29 new virtual levels in the region of 9316–9510 keV excitation energy in⁵¹V were determined. The strong resonance atE _p=1 371 keV has been identified as the isobaric analogue state of the⁵¹Ti ground state by determining spin and parity of this resonance to be 3/2^?. There is no evidence for a strong analogue resonance in⁵¹V corresponding to the 1.16 MeV _{p 1/2} state in⁵¹Ti. The γ-decay of the _{p 3/2} analogue state has been studied by measuring branching ratios and angular distributions of primary γ-transitions with a Ge(Li) detector.M1E2 mixing ratios have been determined for these transitions. The total width of the resonance for γ-decay is found to be Γ_γ=1.6±0.4 eV. New bound levels in⁵¹V have been introduced at 3576, 4651 and 4661 keV excitation energy. TheJ ^π values of the 3085, 4770, and 4863 keV states are determined to be 5/2^?, 5/2^?, 3/2^?, respectively. The analogue-antianalogueM1 transition strength is found to be considerably reduced compared to the situation ins-d shell nuclei.     

Branching ratios and the partial photoionization cross-section for the 3s electron of argon

Binding-energy spectra obtained using the dipole (e, 2e) electron impact coincidence method have been used to derive the 3s/3p cross-section ratios for the photoionization of argon up to 75 eV. The 3s and 3p photoionization branching ratios have been obtained by making use of recently determined double photoionization yields. The partial photoionization cross-section (oscillator strength) for 3s ionization, obtained using the branching ratio and the known total photoionization cross-section, shows the deep minimum ca. 10 eV above threshold which has been predicted by those theoretical calculations which include electron correlation effects. Below 50 eV the cross-section is in excellent agreement with the SRPAE calculation. The results are in close agreement with recent measurements made using synchrotron radiation but are consistently smaller below the minimum and larger at the higher energies.     

无定形靶中离子注入的R,Rp,△Rp的理论计算

本文在Thomas-Fermi势能基础上,导出了全射程R的解析解:R=2/a[E^1/2-A₁(arctg(2E^1/2-f)/△^1/2+arctg f/△^1/2)+B₁ln((E^1/2-f)²)/(E-fE^1/2+d) ·d/f²],其中A₁,B₁,f,d和△均为与离子及靶的质量、原子序数有关的常数。结合导出的η=R/(R_p)(R_p指投影射程)比值的双曲线函数关系 η=F(μ)[A₂(μ)+(B₂(μ))/(ε^1/2+C)],和ω=R_p/△R_p(△R_p指投影射程的标准偏差)比值的线性关系ω=A₃(μ)ε^1/21/2+B₃(μ),可简便而又准确地计算R,△R_p,R_p.这里F(μ),A₂(μ),B₂(μ), B₃(μ)和A₃(μ)为μ的代数函数,μ为离子与靶的质量比,C是经验常数.并对η等关系式的物理意义作了讨论。上述公式的计算结果与Gibbons的数值解结果及有关实验结果作了比较,表明可用于元素半导体如Si、二元化合物如GaAs以及三元化合物如SiO₂等;既对较轻离子适用,也对重离子适用,具有一定的普适范围。     

A study of the 35Cl(p, γ)36Ar reaction and the energy levels of 36Ar

Proton energies and strengths of (p,γ) and (p, p₁) resonances of the ³⁵Cl + p reaction were determined for E_p = 0.4?3.0 MeV and 1.9?3.0 MeV, respectively. The γ-decay of 84 resonances was studied with a 40 cm³ Ge(Li) detector. The branching ratios and excitation energies of 38 bound levels were determined. A new bound level was observed at E_x = 8472.0 ± 1.0 keV. Doppler-shift attenuation experiments yielded lifetimes of 20 bound levels. Spins and/or parities for bound levels and resonances were derived on the basis of observed transition strengths.     

Theoretical lifetimes and branching fractions of 2p4(3P)3d 4D7/2, 2F7/2 and 4F7/2 in Ne II

Transition probabilities of the radiative decay processes of the excited levels 2p⁴(³P)3d ⁴D_7/2, ²F_7/2 and ⁴F_7/2 of the fluorine-like neon ion (Ne⁺) are evaluated by variational calculations using superposition of configurations in the Breit-Pauli approximation. The strong ²F_7/2-⁴F_7/2 relativistic mixing is discussed in terms of level designation and doublet-quartet intensity transfer. A detailed comparison of the results with other theories and with the NIST measurements of branching fractions, combined with lifetime measurements, confirms problems on the experimental side.     

Photoionization branching ratios and asymmetry parameters for inner- and outer-valence shells of H2S in the 18–70 eV energy range

Branching ratios, asymmetry parameters and relative partial cross sections have been obtained for photoionization of the outer and the inner valence shells of H₂S. These measurements were made in the photon energy range 18–70 eV using synchrotron radiation. Our results are compared to a set of calculations using a developed extension of the self-consistent field-Xα scattered-wave method to the continuum states. This comparison shows a qualitative agreement between the experimental and calculated β curves of the outer valence shells. The largely predominant sulfur 3p contribution to the outer valence orbitais 2b₁, 5a₁, 2b₂ is revealed in the corresponding β curves by a Cooper minimum also predicted in the same energy range for the β(3p) of the atomic sulfur. This comparison also shows discrepancies in the branching ratios curves and we suggest that this theoretical framework is better adapted to predict photoionization processes in the outer valence shells than in the inner ones.     

Crystal field splittings and luminescence properties for Nd3+, Er3+ and Dy3+ in yttrium orthoaluminate (YAlO3)

This report contains information appropriate for a theoretical analysis of the optical spectra of triply ionized lanthanides in YAlO₃. Starting with the best-fit crystal field parameters, the crystal field splitting schemes, multiplet-to-multiplet line strengths, radiative lifetimes, branching ratios, line-to-line square matrix elements and g-factors for the triply ionized Nd, Er and Dy in YAlO₃ have been calculated. In this paper detailed discussions were made on the luminescence properties of the principal transitions of Nd-doped YAlO₃ emanating from the metastable ⁴F_{$\text{3}\text{2}$} state to Stark components of multiplets of the ground ⁴I_J term and compared to similar results of Y₃Al₅O₁₂ (YAG). The line-to-line branching ratios were calculated including J-mixing effects. In the calculations, only electric dipole transitions were considered because of odd-parity. The results predicted some interesting differences in the optical behavior of Nd³⁺ in these two host materials. It has been observed that there is a reasonable agreement between the theoretical data and those reported experimentally for YAlO₃ and YAG. The theoretical studies undertaken here were chosen to supplement or extend the optical data for these two host materials.     

Reversible hydrogen-storage functions for mixtures of Li3N and Mg3N2

The hydriding and dehydriding reactions occurring in mixtures of lithium and magnesium nitrides (Li₃N and Mg₃N₂) were investigated for the first time in fixed composition ratios. A mixture of Li₃N–20 at.%Mg₃N₂ after heat treatment at 833 K was hydrogenated at 523 K in 35 MPa according to the following overall reaction: 4Li₃N+Mg₃N₂+12H₂ 12LiH+3Mg(NH₂)₂. This reaction is one of the candidates for reversible hydrogen-storage functions in which 9.1 mass% of hydrogen can be stored in the solid state. PACS 81.05.Zx; 71.20.Ps; 82.30.-b     

Bi2O3-Y2O3系高氧离子导体的离子电导和电子电导的研究

用交流电桥法研究了Bi₂O₃-Y₂O₃体系含22.5—30mol％Y₂O₃烧结试样在po₂值由1至10^-21atm范围内氧离子的电导率,实验证明该种材料的氧离子电导率比同温度下ZrO₂基固体电解质高若干倍;用这种材料作为固体电解质组成氧浓差电池,电池电动势和理论电动势的比值E/E₀等于1或接近1,说明这种材料几乎为纯氧离子导体,p型电子空穴导电性很小;用库伦滴定抽氧法测定了含Y₂O₃ 27.5mol％样品的电子导电特征氧分压,其值为lgp_e＇=(-767000/T)+655,电子导电性极小。可期望为一种新型氧离子导体材料。 关键词：     

Theoretical study on the kinetics for OH reactions with CH3OH and C2H5OH

Kinetics and mechanisms for reactions of OH with methanol and ethanol have been investigated at the CCSD(T)/6-311 + G(3df, 2p)//MP2/6-311 + G(3df, 2p) level of theory. The total and individual rate constants, and product branching ratios for the reactions have been computed in the temperature range 200-3000 K with variational transition state theory by including the effects of multiple reflections above the wells of their pre-reaction complexes, quantum-mechanical tunneling and hindered internal rotations. The predicted results can be represented by the expressions k₁ = 4.65 × 10⁻²⁰ × T^2.68 exp(414/T) and k₂ = 9.11 × 10⁻²⁰ × T^2.58 exp(748/T) cm³ molecule⁻¹ s⁻¹ for the CH₃OH and C₂H₅OH reactions, respectively. These results are in reasonable agreements with available experimental data except that of OH + C₂H₅OH in the high temperature range. The former reaction produces 96-89% of the H₂O + CH₂OH products, whereas the latter process produces 98-70% of H₂O + CH₃CHOH and 2-21% of the H₂O + CH₂CH₂OH products in the temperature range computed (200-3000 K).     

Spectroscopy of Ca3(BO3)2: Dy crystal

Dy³⁺: Ca₃(BO₃)₂ crystal was grown successfully by the Czochraski technique. The absorption spectrum was measured and its absorption peaks were assigned. The Judd-Ofelt intensity parameters were found to be Ω₂=5.216×10⁻²⁰, Ω₄=1.858×10⁻²⁰, Ω₆=0.623×10⁻²⁰ cm². The spectroscopic parameters of this crystal such as the oscillator strengths, radiative transition probabilities, radiative lifetime as well as the branching ratios were calculated. Also, room temperature luminescence decay curve in correspondence with the emission line ⁴F_9/2→⁶H_13/2 centered at 575 nm was measured.     

Spectroscopic analysis and laser parameters of Nd3+ in Ca3Sc2Ge3O12 garnet crystals

3 Sc₂Ge₃O₁₂ (CaSGG) single crystals with the garnet structure have been grown by means of the flux growth technique. The doping with Nd³⁺ and Mg²⁺ (as charge compensator) yields samples suitable for optical spectroscopy experiments. The absorption and emission properties have been measured at temperatures ranging from 10 to 298 K. The emission spectra give evidence of the presence of non-equivalent Nd³⁺ sites. The decay time of the 1.06-μm emission band has been measured as a function of temperature and incident power. The intensities of the 298 K absorption transitions have been analyzed by means of the Judd–Ofelt theory. The radiative lifetimes, the branching ratios (β), and the spontaneous emission probabilities have been evaluated for the ⁴F_3/2 excited state using the calculated intensity parameters. The stimulated-emission cross sections and the branching ratios have been estimated from the experimental data for the most important laser transitions indicating that this crystal can be considered an interesting material for solid-state laser applications. Received: 2 June 1998 / Revised version: 28 October 1998 / Published online: 24 February 1999     

Chloromethane surface chemistry on Fe3O4(1 1 1)-(2 × 2): A thermal desorption spectrometry comparison of CCl4, CBr2Cl2, and CH2Cl2

The surface chemistry of CBr₂Cl₂ on the Fe₃O₄(1 1 1)-(2 × 2) selvedge of single-crystal α-Fe₂O₃(0 0 0 1) has been investigated using temperature programmed reaction and desorption (TPR/D) measurements. The spectra obtained in this case show that strong chemisorption occurs and that a series of adsorbed halogenated reaction products are present. By comparison, studies of the adsorbed phase of CH₂Cl₂ show that only physisorption occurs. The TPR/D spectra of CBr₂Cl₂ show that dissociative formation of CCl₂ followed by its reaction with lattice oxygen is central to the monolayer reaction chemistry in this chloromethane. The branching ratios of the various desorbed products are compared with those obtained from CCl₄ adsorbed on the same (2 × 2) surface.     

Ion-electron coincidence study of the thermal He(23S) + H2 Penning reaction

A new Penning-electron-Penning-ion coincidence method is described. It is applied to the study of the thermal reaction of He(2³S) with H₂. The main results reported are separate electron energy spectra that are coincident with the three different ions formed: HeH₂⁺, HeH⁺ and H₂⁺. Based on these results it is shown that the Penning reaction of the He(2³S)/H ₂ system proceeds in two well-separated steps: (i) ionization at distances R (HeH₂) ? 6a₀ in which H₂⁺ (v) is formed in different vibrational states; and (ii) reactive collision of H₂⁺ (v) with He. For the second step the variation of the branching ratios with vibrational quantum numbers v = 0 to v = 10 is derived, and it is shown that these branching ratios may be regarded as relative vibrational-energy-dependent cross-sections for the collision of H₂⁺ (v) with He at an average relative kinetic energy of ～20 meV.     

A study of np annihilations around 0.65 GeV/c

$\text{n}\text{p}$ annihilations with ? 3 prongs with an incident antineutron momentum between 0.5 and 0.8 GeV/c are analysed. We present the topological branching ratios and cross sections, the resonance production rates and possible ?-ω interference effects.     

Charmonium-the 1P1 state

Based on a model which gives agreement with the observed hyperfine and fine splitting of the charmonium states, we predict the mass of ¹p₁ to be 3372 MeV, substantially lower than any previous predicted values. We have also estimated branching ratios and decay rates for the production of this state via channels which become accessible because of its low mass.     

MULTIPHOTON IONIZATION MASS SPECTRA OF n-C3H7I AND i-C3H7I AT 532 nm

Multiphoton Ionization (MP) Mass Spectra of n-C₃H₇I AND i-C₃H₇I are obtained using a time-offlight mass spectrometer at 532 nm. No parentions are observed in MPI of both isomers. N-propyl cation dissociates more extensively than isopropyl cation. The C₂H⁺₅(M/Z=29) ion is observed instead of C₂H⁺₄(M/Z=28) ion in MPI of n-C₃H₇I, in contrast to i-C₃H₇I. It is found that parent molecules are first two-photon resonantly excited to A-band, then go through dissociation. Fragment ions are produced by ionization and dissociation of neutral fragments. We present directly the diss ociation pathways of n-propyl cation according to the results proposed by Levine using maximum entropy formalism. Moreover, those of isopropyl cation are discussed in this paper through branching ratio analyses.     

Core polarisation effect on the 3p 1/2, 3p 3/2, 2f 5/2, 2f 7/2 and 1i 13/2 proton states of209Bi

The weak fragments of the 3p_1/2, 3p_3/2, 2f_5/2, 2f_7/2 and 1i_13/2 proton states of²⁰⁹Bi as seen in the²⁰⁸Pb (³He,d) reaction can be explained with the coupling of the renormalised proton states and the vibrational states of²⁰⁸Pb. The energies of the zerothorder proton shell-model states as well as the collective admixtures of the weak fragmented proton states of²⁰⁹Bi have been deduced from the core-particle coupling model.