Decay of Rydberg states in the field of a highly charged ion

The quasi-stationary spectrum of highly excited (Rydberg) states in the field of a multiply charged ion is calculated in the asymptotic region. The result is used to obtain the electron transfer cross section, within the decay approximation, for the process.     

Ionization of Hydrogen and Helium Atoms in Collisions with Relativistic Structural Heavy Ions

Based on the eikonal approximation, cross sections for single and double ionization of hydrogen and helium atoms in collisions with structural multiply charged heavy ions moving with relativistic velocities are calculated. In the present paper, the structural ions are taken to mean the ions with partially filled electronic shells. It is demonstrated that a consideration of the ion charge extension may noticeably change the corresponding cross sections compared to the cross sections for ionization by point ions having the same charges and energies.     

Neutralization of H− ions in collisions with fast, multiply charged ions

The neutralization of H⁻ ions in collisions with fast, multiply charged ions is considered in the parameter region where the Born approximation applies. An analytical formula is obtained for the H⁻ neutralization cross section in such collisions. Zh. Tekh. Fiz. 69, 1–4 (July 1999)     

One-electron capture from the inner shells in atom-multicharged ion collisions

The electron capture from the inner atomic shells by multiply charged ions at intermediate and high collision energies is considered. The cross section scaling laws, as well as the reduced energy parameter, are discussed. Universal curves for the reduced cross section versus the reduced collision energy are presented for electron capture from the K, L and M shells of Ar atoms colliding with multiply charged ions. A comparison of theoretical results with the existing experimental data is given.     

Leading log radiative corrections to deep inelastic neutral and charged current scattering at HERA

TheO(α) radiative corrections for neutral and charged current deep inelastic scattering are calculated in the leading log approximation. The numerical results are found to agree within a few per cent with the results of a completeO(α) calculation by Bardin et al. It is demonstrated that both for the leading log and completeO(α) calculation all light quark mass terms can be eliminated from the cross section.     

CHARGE EXCHANGE CROSS SECTIONS FOR MULTIPLY CHARGED IONS COLLIDING WITH HYDROGEN ATOM

An empirical relation is proposed for the charge-exchange cross section of multiply charged ions colliding with hydrogen atom. This relation, useful for incident energy E in the range 10 keV/a.m.u.<E≤24 keV/a.m.u. has been tested for different charge states of C, N, O, He, Li and Fe.     

Inelastic scattering of charged particles by atoms using the Thomas-Fermi statistical method

We describe a method of calculating the differential cross section for the inelastic scattering of charged particles by atoms based on the statistical model of the atom. For the most general form of the potential of the atom we obtain an analytical expression for the differential (with respect to the energy of the electron ejected from the atom) cross section of inelastic scattering. It is shown that the statistical method of Thomas-Fermi is applicable when the energy of the ejected electron is sufficiently high.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 92–96, September, 1986.     

Resonance inelastic scattering of an x-ray photon by a Ne-like atomic ion

The absolute values and the shape of the double differential cross sections of the resonance inelastic scattering of a linearly polarized x-ray photon in the energy region of the ionization threshold of the deep 1s shell of the Ne atom and the Si⁴⁺ and Ar⁸⁺ neon-like ions are calculated in the nonrelativistic approximation for the wave functions of one-electron states and in the dipole approximation for the scattering probability amplitude. The multiparticle effects of radial relaxation of electronic shells in the field of a deep vacancy and of stabilization of the deep vacancy as a neutral atom transforms to a multiply charged positive ion, as well as the effect of the spin-orbit splitting of the 2p valence shell, are taken into account. The calculation results are predictive in character.     

Tagged-photon events in polarized deep inelastic scattering

Deep inelastic scattering events of a longitudinally polarized electron by a polarized proton with a tagged collinear photon radiated from the initial-state electron are considered. The corresponding cross section is derived in the Born approximation. The model-independent radiative corrections to the Born cross section are also calculated. The obtained result is applied to the elastic scattering.     

Scattering of excitons by excitons in semiconducting quantum well structures

We have theoretically investigated the scattering of excitons by excitons in a two-dimensional semiconducting quantum well system. The scattering cross sections have been calculated using the Born approximation for both the elastic and inelastic scattering of the excitons by excitons. The threshold for inelastic scattering is increased over the value in a bulk semiconductor because of the enhancement of the exciton binding energy by its confinement. The behavior of the scattering cross section as a function of the energy of relative motion of the excitons is different than in the bulk and the cross section is a more sensitive function of the ratio of the electron and hole masses than in the bulk.     

(e,2e)反应中冲量近似的理论研究

利用冲量近似理论和玻恩近似方法, 以氢原子(1s)为例, 在共面不对称几何条件下用多种模型分别计算了若干入射能、 散射角情形下电子碰撞电离(e, 2e) 反应的三重微分散射截面. 与其他的理论方法和实验数据进行了比较, 分析了曲线结构差异及原因, 对其适用范围进行了研究, 并探讨了交换效应的贡献, 验证了早期的研究. 关键词： 扭曲波冲量近似 平面波冲量近似 三重微分截面     

Thermal effects on neutrino-nucleus inelastic scattering in stellar environments

Thermal effects for inelastic neutrino-nucleus scattering off even-even nuclei in the iron region are studied. Allowed and first-forbidden contributions to the cross sections are calculated within the quasiparticle random-phase approximation, extended to finite temperatures within the Thermo-Field-Dynamics formalism. The GT₀ strength distribution at finite temperatures is calculated for the sample nucleus ⁵⁴Fe. The neutral-current neutrino-nucleus inelastic cross section is calculated for relevant temperatures during the supernova core collapse. The thermal population of the excited states significantly enhances the cross section at low neutrino energies. In agreement with studies using a large scale shell-model approach the enhancement is mainly due to neutrino up-scattering at finite temperatures.     

Electron capture by slow multiply charged Ar and Ne ions from atomic hydrogen

At collision energies below 15 keV total charge transfer cross sections have been measured for multiply charged Ar^ζ+(2≦ζ≦6) and Ne^ζ+(2≦ζ≦4) ions colliding with atomic hydrogen. A Wood discharge was used to provide a hydrogen target with a sufficiently high degree of dissociation. Results are compared with measurements performed at higher energies and with theoretical calculations. For ζ=2 cross sections in atomic hydrogen are much smaller than in the molecular case, for ζ>2 the ratio of these cross sections varies between 0.7 and 1.6.     

He同位素对He-NO碰撞体系微分截面的影响

用密耦近似方法计算了同位素He原子与NO分子碰撞体系的总微分截面、弹性微分截面和非弹性微分截面,总结了同位素He原子对He-NO碰撞体系微分截面的影响. 计算结果表明：在同一入射能量下,随着入射同位素He原子质量增加,总微分截面在0°时的角分布逐渐增大;同位素He原子与NO分子碰撞发生的彩虹现象越明显. 同时,体系约化质量增加的效应大于相对碰撞速度减小的效应,使散射振荡间隔逐渐减小. 关键词： He-NO 密耦近似 微分截面 同位素效应     

Emission in the final state in processes with the production of charged pions and light leptons

The Drell-Yan form is proposed for the decay widths of heavy quarks and cross sections for high-energy scattering with the production of charged pions and light leptons including radiative corrections in the final state in the leading logarithmic approximation. The corresponding spectral distributions are given in terms of the convolution of the cross section (decay width) in the Born approximation with the structure functions of pions and leptons. The pion structure function is given in the explicit form.     

Effect of elastic scattering on the kinetics of mesic atom formation

The differential, total and transport elastic cross sections are calculated with an adiabatic effective (µ^––H) potential and with regard to inelastic transitions. The elastic cross section is greater than the inelastic one by an order of value in the atomic-capture energy region. The excess increases with particle mass. The effect of the elastic scattering on the energy distribution of Coulomb capture is considered within the approximation of continuous elastic energy losses. An appreciable increase of the capture probability due to elastic scattering is obtained in the low-energy region.     

20MeV以下快中子与56Fe非弹性散射截面的分歧研究

56Fe的非弹性散射截面在核装置中子输运计算中扮演着重要的角色,但无论从实验数据还是从评价数据,非弹性散射截面都存在很大分歧,它的数据直接影响到核装置的设计、建造与运行维护。本工作从实验数据本身出发,深入分析了不同实验室测得的847 keV的γ产生截面的分歧,经转化后补充非弹性散射截面的实验空白能区,并同时利用满足全截面、去弹截面等截面自洽关系的评价方法推荐了高精度的快中子与56Fe的非弹反应截面结果。积分检验表明,新的非弹截面的改进使得评价数据与积分实验结果一致,较CENDL-3.1的评价数据结果有显著改善。Knowledge about the inelastic scattering cross section of 56Fe is very important in neutron transportation calculation. However there are great discrepancies not only between experimental data but also between evaluated data. More detail analysis was performed for inelastic scattering cross section in the fast range up to 20 MeV where there are significant differences among the main evaluated libraries, mainly caused by the different inelastic scattering cross section measurements. The large discrepancies on 56Fe(n, n₁'γ) cross section which could fill the neutron energy blank of the 56Fe(n,inl) were clarified and were converted to the inelastic scattering cross section of 56Fe. And the high-quality results were evaluated by using the unitarity constrain among total cross section, noelastic reaction and other reactions. The integral experiment result indicates that the new evaluated result of inelastic cross section brings greater improvement than that of CENDL-3.1.     

Electron-impact ionization and dissociative ionization of sulfur in the gas phase

We describe the methods and the results of investigation of the yield of positive ions formed as a result of electron-impact ionization of sulfur. The ionization energy for the basic molecule and the energies corresponding to the emergence of fragment ions are obtained from the ionization efficiency curves. The dynamics of formation of molecular sulfur ions in the temperature range 320–700 K is investigated. The energy dependences of efficiency S _n of the ion formation for n = 1–6 are analyzed, and their appearance energies are determined. The total cross section of sulfur ionization by a monochromatic electron beam is also investigated. Using the linear approximation method, we marked out features on the ionization function curve, which correspond to the ionization and excitation energies for multiply charged ions. The total cross section of the formation of negative sulfur ions is measured in the energy range 0–9 eV.     

中子与116,118,120,122,124Sn反应非弹性散射的理论计算和分析

应用现有的中子与原子核Sn及其同位素反应的总截面,去弹性散射截面,弹性散射截面和弹性散射角分布的实验数据,获得一组普适的中子与Sn及其同位素反应的光学模型势参数.利用这组光学模型势参数,扭曲波玻恩近似理论,核反应Hauser-Feshbach理论和预平衡反应的激子模型,计算和分析了中子与^{116,118,120,122,124}Sn反应分离能级的非弹性散射截面和角分布.理论计算与实验数据进行了分析比较.     

中等光强纳秒激光电离苯团簇产生多价碳离子的数值模拟和实验研究

飞秒强激光与团簇相互作用产生多价离子的现象已被广泛报道,然而近期多个研究小组发现当功率密度低至1010W/cm2的纳秒激光照射团簇时,同样也观察到了多价离子的存在.虽然可以用"多光子电离引发-逆韧致吸收加热-电子碰撞电离"电离机理对这种现象进行解释,但是缺乏相应的数值模拟.建立了一个简化的数值模型,根据有质动力势Up计算团簇内电子能量,再由Lotz公式计算出相应的电离截面,最后由动力学反应速率方程计算出团簇内多价碳离子随时间的演变.详细分析了团簇尺寸、电子密度等关键参数对多价离子产生的影响.数值模拟结果表明:团簇电离在小于0.7 ns时间尺度内完成,C2+,C3+和C4+多价离子强度达到平衡后,离子相对强度由大到小依次为C2+,C3+,C4+,这与实验结果相一致;多价离子的价态随着团簇尺寸的增加而升高,半径为5.6 nm的苯团簇比半径为3 nm的苯团簇更容易产生高价态的离子,这也与实验结果相一致.