乙炔分子的低能电子弹性散射研究

本文采用R矩阵方法研究低能电子与乙炔分子的弹性散射截面及其动力学过程.研究采用静态交换势模型(SE)和静态交换加极化势模型(SEP)两种方法.结果显示当前SEP模型预测的弹性散射截面与已有的实验值和理论结果符合的很好.SE模型预测了一个位于4.75 eV,宽度为3.0 eV的π形状共振态.该共振态在SEP模型中的位置降低为2.65 eV,宽度为1.5 eV.它来自B_(2g)和B_(3g)对称性贡献,理论预测共振态位置与实验值符合的很好.我们讨论了考虑不同的虚轨道对共振态的影响,说明预测精确的共振态的位置需要准确的处理极化效应.基于SEP模型得到的K矩阵元,我们使用POLYDCS代码计算的散射微分截面(DCS),和实验值符合的较好.除此之外,我们还报道了2 eV时转动分辨的态-态微分截面.     

基态H和Br原子的低能弹性碰撞研究

利用分波法研究了低温及极低温下基态H和Br原子沿HBr(X1Σ+)分子相互作用势发生的弹性碰撞. 在1.0×10-11-1.0×10-3 a.u.的碰撞能区内通过数值求解原子-原子碰撞的薛定鄂方程, 计算了这一弹性碰撞的总截面和各分波截面, 讨论了各分波截面对总弹性截面的贡献. 结果表明在非常低的温度下这一弹性散射的总截面值很大、且几乎为一常数. 分析指出在极低能区内总弹性截面的形状主要由s分波截面的形状决定. 在总弹性截面上存在着2个较强的形状共振, 一个位于2.276×10-4 a.u., 另一个位于4.440×10-4 a.u. 计算表明前者主要来自于f和g分波的联合贡献, 后者主要来自于l = 5和l = 7分波的联合贡献. 虽然在f分波上还存在一个形状共振、且在直到l = 8的其它分波中也都存在强度不同的形状共振, 但它们都被淹没在较强的总弹性截面中. 同时计算还表明, 高于l = 10的分波对总弹性截面已无实质贡献.     

惰性气体原子对2500eV电子的绝对弹性散射微分截面

在入射电子能量为2500eV，散射角为4°—15°的条件下测量了氦、氖、氩的相对弹性散射微分截面，并采用非弹性散射的广义振子强度为标准进行刻度，得到了2500eV能量下的绝对弹性散射微分截面值.所得结果与前人的理论和实验结果作了比较. 关键词：     

BeCl_2分子的低能电子弹性散射研究

基于R矩阵理论方法,通过构建BeCl_2分子的静态交换势模型(SE),静态交换加极化势模型(SEP)和密耦合模型(CC),在0-10 eV能量范围内首次研究了低能电子与BeCl_2分子的散射动力学过程,预测了弹性散射积分截面,并在三种模型中分别发现一个来自B_(2u)和B_(3u)对称性贡献的势形共振态.讨论了这些共振态随着极化效应的变化,获得了收敛的截面和共振态结果.进一步使用POLYDCS程序首次计算了电子与BeCl_2分子的散射微分截面(DCS)以及动量转移截面(MTCS).当前研究结果将为天体物理和等离子体物理提供重要的截面数据.     

电子氢原子碰撞电离能量微分截面和总截面的理论计算

利用扭曲波玻恩交换（ＤＷＢＥ）近似方法对电子－氢原子碰撞电离截面进行了计算，计算所得总截面和能量微分截面均与最新的实验结果进行了比较，比较结果显示本计算与实验有较好的符合。还给出了能量微分截面的高斯拟合公式，文中对实验与理论计算存在的一些差距进行了讨论。 关键词：     

快中子在Li核上的弹性散射微分截面

用伴随粒子飞行时间法测量了14.7MeV中子在⁶Li和⁷Li核上的弹性散射截面,并用蒙特卡罗方法对中子在样品中的通量衰减、多次散射作了修正.本文工作与他人工作以及理论数据作了比较.给出了截面的勒让德系数;截面实验点总误差在10%到15%之间,其中统计误差为1%-5%.     

H＋F弹性碰撞微分截面的计算

采用经典力学的方法对Ｈ与Ｆ碰撞动力学问题进行了研究,计算了碰撞的轨迹,偏转函数和微分截面。ＨＦ（Ｘ＾１Σ＾＋）的势能函数采用Ｍｕｒｒｅｌ－Ｓｏｒｂｉｅ函数形式。     

14.2MeV中子在锆上弹性散射的微分截面

用伴随粒子飞行时间方法,在10°—140°范围内测量了14.2MeV中子在Zr上的弹性散射微分截面.用蒙特卡洛方法对中子在样品中的通量衰减,多次散射及有限角分辨进行了修正;并将测量数据与光学模型理论计算及他人的结果作了比较.     

类氦离子的电子碰撞电离微分截面

本文主要利用扭曲波玻恩交换近似方法(DBE)计算类氦离子在电子碰撞下,相应不同的末态电子能量分配的电离截面(能量微分截面)。发现对这些微分截面在不同靶电荷及入射能量下,都可用带两个参数的高斯函数αexp(β(x—0.5)²)很好地拟合。还给出两个拟合参数随靶电荷和入射能量的变化曲线,以及讨论了在库仑波玻恩交换近似(CBE)和DBE两种不同近似下所得参数值的差别。计算结果也表阴,在低靶电荷和低入射能量时用DBE计算的必要性。 关键词：     

Elastic Collisions Between two Ground-State P and D Atoms at Low and Ultralow Temperatures

The PD（X^3∑^-） interaction potential is constructed using the CCSD（T） theory and the basis set, augcc-pV5Z. Using this potential, the spectroscopic parameters are accurately determined. The present Do, De, Re, ωe, ωeχe, αe, and Be are of 3.056 99 eV, 3.161 75 eV, 0.142 39 nm, 1701.558 cm^-1, 23.6583 cm^-1, 0.085 99 cm^-1, and 4.3963 cm^-1, respectively, which almost perfectly conform with the measurements. A total of 26 vibrational states is predicted when J = 0 by solving the radial Sehrodinger equation of nuclear motion. The complete vibrational levels, classical turning points, initial rotation and centrifugal distortion constants when J = 0 are reported for the first time, which favorably agree with the experiments. The total and various partial-wave cross sections are calculated for the elastic impact between two ground-state P and D atoms at 1.0 × 10^-12 - 1.0 × 10^-4 a.u. when they approach each other along the PD（X^3∑^-） potential. No shape resonances exist in the total elastic cross sections, though the peaks can be found for each partial wave until l=6. The shape of the total elastic cross sections is dominated by the s partial wave at very low temperatures. Due to the weakness of the shape resonances of each partial wave, they are all passed into oblivion by the strong total elastic cross sections.     

丝氨酸异构体的电子-分子形状共振态及其解离动力学理论研究

Shape resonances of electron-molecule system formed in the low-energy electron attachment to four low-lying conformers of serine (serine 1, serine 2, serine 3, and serine 4) in gas phase are investigated using the quantum scattering method with the non-empirical model potentials in single-center expansion. In the attachment energy range of 0-10 eV, three shape resonances for serine 1, serine 2, and serine 4 and four shape resonances for serine 3 are predicted. The one-dimensional potential energy curves of the temporary negative ions of electron-serine are calculated to explore the correlations between the shape resonance and the bond cleavage. The bond-cleavage selectivity of the different resonant states for a certain conformer is demonstrated, and the recent experimental results about the dissociative electron attachment to serine are interpreted on the basis of present calculations.     

Elastic scattering of two ground-state N atoms

An interaction potential for an N₂(X¹σ_g⁺) molecule is constructed by using the highly accurate valence internally contracted multireference configuration interaction method and the largest basis set, aug-cc-pV6Z, in the valence range. The potential is used to investigate the elastic scattering of two N atoms at energies from 1.0× 10^-11 to 1.0× 10^-4 a.u. The derived total elastic cross sections are very large and almost constant at ultralow temperatures, and the shape of total elastic cross section curve is mainly dominated by the s-partial wave at very low collision energies. Three shape resonances are found in the total elastic cross sections. Concretely, the first one is very sharp and strong. It results from the g-partial-wave contribution and the resonant energy is 3.645× 10^-6 a.u. The second one is contributed by the h-partial wave and the resonant energy is 1.752× 10^-5 a.u. This resonance is broadened by those from the d- and f-partial waves. The third one comes from the l = 6 partial wave contribution and the resonant energy is 3.522× 10^-5 a.u. This resonance is broadened by those from the g- and h-partial waves. The N₂(X¹σ_g⁺) molecular parameters, which are determined at the current theoretical level, achieve very high accuracy due to the employment of the largest correlation-consistent basis set in the valence range.     

Elastic collisions of sulfur and hydrogen in their ground states at low temperatures and spectroscopic parameters of SH（X^2∏） radical

This paper constructs the interaction potential of the SH（X^2∏） radical by using the coupled-cluster singlesdoubles-approximate-triples theory combining the correlation-consistent quintuple basis set augmented with the diffuse functions, aug-cc-pV5Z, in the valence range. Employing the potential, it accurately determines the spectroscopic parameters. The present De, Re, ωe, ωeχe, ae and Be values are of 3.7767eV, 0.13424nm, 2699.846 cm^-1, 47.7055 cm^-1, 0.2639cm^-1 and 9.4414 cm^-1, respectively, which are in excellent agreement with those obtained from the measure- ments. A total of 19 vibrational states has been found when J = 0 by solving the radial SchrSdinger equation of nuclear motion. The complete vibrational levels, classical turning points, initial rotation and centrifugal distortion constants when J = 0 are reported for the first time, which are in good accord with the experimental results. The total and various partial-wave cross sections are computed for the elastic collisions of sulfur and hydrogen in their ground states at low temperatures when two atoms approach each other along the SH（X^2∏） potential energy curve. Over the impact energy range from 1.0×10^-11 to 1.0×10^-4 a.u., eight shape resonances have been found in the total elastic cross sections. For each shape resonance, the resonant energy is accurately calculated. Careful investigations have pointed out that these resonances result from the 1 = 0, 1, 2, 3, 4, 6, 7, 8 partial-wave contributions.     

Elastic electron scattering with CH2Br2 and CCl2Br2: The role of the polarization effects

We present elastic electron scattering cross sections with holmethane molecules CH₂Br₂ and CCl₂Br₂ in the low-energy region ranging from 0.01 eV to 20 eV. The calculations are performed with the R-matrix method in static-exchange plus polarization (SEP) and close-coupling (CC) approximations. The integral, differential, and momentum transfer cross sections are calculated. The convergence of the obtained cross sections is checked at four different levels of SEP approximation. The predicted positions of the resonances agree well with available results. The precise resonance parameters are found to be sensitive to the treatment of polarization effects employed. We find that the polarization has a substantial effect on the cross sections, and this effect becomes even more important for lower impact energies.     

Elastic scattering for the system 11Be + 209Bi at Coulomb barrier energies

The elastic scattering process for ¹¹Be ions impinging on a ²⁰⁹Bi target was studied in the energy range around the Coulomb barrier. The angular distributions of the ¹¹Be scattered particles were analyzed within the optical model framework in order to evaluate the reaction cross section, which turned out to be much larger than the fusion one, especially in the sub-barrier region. The comparison with the system ⁹Be + ²⁰⁹Bi showed that the reaction cross section is larger for the reaction ¹¹Be + ²⁰⁹Bi in the energy range around the Coulomb barrier, while they are rather similar at higher bombarding energies. This result suggests that direct processes related to the ¹¹Be halo structure and lower binding energy are more relevant at near-barrier energies.     

超低温下钠原子散射特性研究

超低温下钠原子的散射特性对原子间的相互作用势非常敏感.本文基于构造精确的原子间相互作用势,详细研究了在超冷温度下处在超精细态|F=2,mF=2〉下23Na原子的弹性散射特性.我们分别用Numerov和半经典方法计算了散射长度和有效程,得到了较满意的结果.低能散射截面有丰富的共振现象产生,我们发现并给出了d-波和g-波形状共振的能级位置和共振宽度;此外,我们还对仅两个分波有贡献情况下的微分散射截面进行了理论计算.     

Resonances and Threshold Phenomena in Low-Energy Electron Collisions with Hydrogen Halides: New Experimental and Theoretical Results

Low-energy electron collisions with HCl and HBr and the deuterated compounds have been investigated by experimental and theoretical methods. New experimental results have been obtained on relative differential cross-sections for vibrational excitation and dissociative electron attachment. Measurements with high energy resolution for rotationally cooled molecules have revealed, in addition to shape resonance, threshold peaks and Wigner cusps, the existence of surprisingly sharp oscillatory structures in the elastic and v = 0 1 vibrational excitation cross-sections in a narrow range below the dissociative attachment threshold. The theoretical analysis is based on an improved nonlocal resonance model which has been constructed on the basis of ab initio fixed-nuclei scattering phase shifts for HCl and HBr and accurate ab initio calculations of the bound part of the HCl^– and HBr^– potential-energy functions. The high degree of agreement which has been obtained between experiment and theory for all channels indicates that the mechanisms responsible for the rich threshold structures in the collision cross-sections are completely understood.