0.5 eV时H++D2(v=0,j=0) 反应的微分、积分截面

基于ab initio势能面(KBNN PES)[1],用耦合通道超球坐标理论研究了碰撞能等于0.5 eV时H D2(v=0,j=0)的积分,微分截面.对于反应性碰撞,计算的积分截面表明由于深势阱的存在使得这一绝热反应产物的分布表现出一种近似的统计行为.计算的微分截面反映该体系存在着长寿命的中间络合物;对于非反应性碰撞(传能过程),平动—平动传能过程更有效,且其积分截面随着转动量子数的增大而显著减少.通过反应性碰撞和非反应性碰撞积分截面的比较,发现在低能碰撞情况,非反应性碰撞更容易进行.     

计算中低能量电子与水分子弹性散射微分截面

运用耦合通道光学势方法计算了在中低能量下的电子与水分子碰撞弹性散射微分截面,其中靶的极化效应被包含在一个从头算的等价局域势中.随后将计算结果与实验值和其它理论计算结果进行了比较.结果显示这种计算方法对于电子与极化分子体系碰撞是非常适用的.     

He-NO碰撞体系微分截面的理论计算

首先用Huxley势函数形式拟合了在RCCSD(T)/aug-cc-pVTZ+bf理论水平下计算的He-NO相互作用能数据，获得了He原子与NO分子相互作用的各向异性势，然后采用密耦近似方法计算了He-NO碰撞体系的总微分截面、弹性微分截面和非弹性微分截面，并总结了微分散射截面的变化规律. 结果表明，拟合势不但表达形式简洁，而且较好地描述了He-NO系统相互作用的各向异性特征；利用碰撞体系分子间势的量子化学从头计算结果,可解决势能参数难以确定的问题，对进一步研究原子与分子碰撞机理有一定参考价值. 关键词： 各向异性势 势能参数 密耦近似 微分截面     

He-N2碰撞体系散射截面的理论研究

本文运用量子化学从头计算MP2方法6-311 G(3df,2p)基组,计算了He-N2相互作用的势能,拟合出He原子与N2分子相互作用的各向异性势函数,其势函数参数:势能球平均势阱位置、势阱深度、势能零点位置与通过散射实验数据分析的ESMSV(Exponential-Spline-Morse-Spline-Van der waals)势比较吻合.然后,用公认精确度高的密耦方法计算了He原子与N2分子碰撞体系的总微分截面、弹性微分截面、转动激发的非弹性微分截面和积分截面,计算结果与实验数据符合得较好.     

核子与镜象核~3H和~3He弹性散射中电荷对称破环效应

采用微观的动量空间光学势及R.Crespo和J．A．Tostevin建议的处理动量空间库仑作用的方法,计算了500MeV的核子与镜象核3H和3He弹性散射微分截面,截面比r1,r2和超比R．理论计算结果r1,r2和R均不等于1,显示出由于p-核库仑作用直接引起的电荷对称破坏效应．     

Shape resonances of oriented molecules: ab initio theory and experiment on hydrocarbon molecules

We report ab initio calculations of the x-ray absorption cross section for the near edge x-ray absorption fine structure of C2H6, and C2H4, and C2H2 at the C K-edge, based on a full multiple scattering formalism. The angular dependence of the electric dipole transition in the calculations as well as the angular dependent experiments for the oriented molecules give a good opportunity to compare both. The resonance can be assigned to a sigma(*) shape resonance. The multiple scattering formalism and the experiment agree well and thereby support the existence of such features in the spectra.     

Total differential scattering cross section of Ar+-Ar at 15 to 400 keV

We report on the measurement of the total differential scattering cross section of Ar⁺-Ar at laboratory energies between 15 and 400 keV. Using an ab initio relativistic molecular program which calculates the interatomic potential energy curve with high accuracy, we are able to reproduce the detailed structure found in the experiment.     

运用球高斯分布极化势研究低能电子与H2 分子碰撞的振动激发动量迁移散射截面

用最近改进的球高斯分布(distributed spherical Gaussian,DSG)极化势模型,在振动密耦合框架下和基于量子力学从头计算的静电势、交换势的基础上,研究了低能电子与H₂分子碰撞振动激发的动量迁移散射截面(momentum transfer cross section,MTCS).通过包含18个振动波函数、5个分波和16个分子对称性,得到了0<E≤10 eV时收敛性很好的ν=0→ν'=0,1,2,3等几个振动跃迁通道和总的MTCS,并与其他实验和理论得到的值进行了比较和分析. 关键词： 2分子碰撞')" href="#">H₂分子碰撞 动量迁移散射截面 振动激发 球高斯分布极化势     

Efective Parameters on Energy Losses of Fast Electron in Fusion Mediums

The stopping and scattering of fast electrons in a dense plasma relevant to inertial confinement fusion(ICF)are investigated numerically with the latest improved cross section equations.Binary and collective efects are considered to determine beam transport parameters such as range,penetration depth,spreading processes as straggling and blooming versus electron energy and plasma parameters.Blooming and straggling efects,which act as consequences of scattering with statistical assumption in collisions,lead to a non-uniform,extended region of energy deposition.Finally the mean angle of deflections is calculated for diferent plasma energies.     

Effective Parameters on Energy Losses of Fast Electron in Fusion Mediums

The stopping and scattering of fast electrons in a dense plasma relevant to inertial confinement fusion (ICF) are investigated numerically with the latest improved cross section equations. Binary and collective effects are considered to determine beam transport parameters such as range, penetration depth, spreading processes as straggling and blooming versus electron energy and plasma parameters. Blooming and straggling effects, which act as consequences of scattering with statistical assumption in collisions, lead to a non-uniform, extended region of energy deposition. Finally the mean angle of deflections is calculated for different plasma energies.     

Low energy elastic differential electron scattering from H2O

Normalized differential cross sections for elastic (rotationally averaged) electron scattering from gaseous water (H2O) are obtained using the relative flow method against helium with a thin aperture collimating source of gas instead of a tube. This method obviates the use of gas kinetic molecular diameters for helium or water. Our measurements are found to be largely in quantitative disagreement with past differential elastic electron scattering measurements and suggest that present recommended electron scattering total cross sections for water be revised.     

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.     

Model differential cross section of elastic scattering of electrons by atoms in the Monte Carlo simulation of the passage of electrons in a substance

A new model differential cross section is proposed for describing elastic scattering of electrons in simulating the passage of electrons through a substance by the Monte Carlo method. This differential cross section correctly describes the first and second transport scattering cross sections, but is characterized by the total elastic scattering cross section much smaller than the actual value of the total elastic scattering cross section. The application of this differential cross section makes it possible to considerably reduce the number of elastic collisions in the Monte Carlo simulation of passage of electrons in a substance and to model the passage of high-energy electrons using the individual collision model.     

Nondipole effects in photo-double-ionization of He by a vuv photon

We present a dynamical model-independent, ab initio parametrization of the quadrupole transition amplitude for photo-double-ionization of He. An asymmetry of the triple differential cross section induced by the nondipole corrections is discussed and shown to be significant even for an excess energy as low as 80 eV. We provide predictions for two different kinds of experiments in which nondipole effects should be observable with current experimental capabilities.     

Ar-H2(D2, T2)碰撞体系的振转相互作用势及散射截面的理论计算

用量子力学从头算的耦合族CCSD(T)方法, 使用相关一致基组aug-cc-pV5Z并加3s3p2d1f1g高斯键函数计算了Ar原子与H₂分子的振转相互作用和电荷分布, 采用Boys和Bernardi提出的均衡法消除了基组重叠误差(BSSE). 然后用Tang-Toennies势能函数拟合得到Ar-H₂体系相互作用势的解析表达式. 在该相互作用势下, 用密耦方法计算了Ar原子入射能量为83 meV时, Ar-H₂(D₂, T₂)碰撞体系的散射截面. 计算Ar-D₂体系的微分截面与实验值比较符合很好. 计算结果及分析表明, 在长程吸引势的散射中, 色散能起主要作用; 在短程排斥势的散射中, 交换能起重要作用. 当碰撞参数在0.27 nm至0.47 nm的范围时, Ar-H₂(D₂, T₂)碰撞体系的径向偶极发生两次转向.     

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.     

Electron Raman scattering of a hydrogenic impurity in a disc-shaped quantum dot

We have carried out the theoretical calculation of the differential cross section for the electron Raman scattering process associated with a hydrogenic impurity in a disc-shaped quantum dot (QD). We consider the impurity states confined in a disc-shaped QD with parabolic potential in the presence of an external electric field. Effects of the electric field and the confinement strength on the differential cross section are investigated. We make a comparison about the Raman intensity between with and without the Coulomb interaction. We found that the differential cross section of the hydrogenic impurity in a disc-shaped QD dependent strongly on the confinement strength, the external electric field intensity and the Coulomb interaction.     

Quantum effects in the differential cross Ssctions for the insertion reaction N(2D) + H2

The quantum (QM) scattering theory has been difficult to apply to the family of insertion reactions and the approximate quasiclassical trajectory (QCT) method or statistical calculations were mostly applied. In this Letter, we compare the experimental differential cross sections for the title insertion reaction with the results of QM and QCT calculations on an ab initio potential energy surface. The QM results reproduce well the crossed beam experiment, while a small, but significant, difference in the QCT ones points to quantum effects, possibly the occurrence of tunneling through the combined potential and centrifugal barrier.     

Ab initio many-body calculations of the (3)H(d,n)(4)He and (3)He(d,p)(4)He fusion reactions

We apply the ab initio no-core shell model combined with the resonating-group method approach to calculate the cross sections of the (3)H(d,n)(4)He and (3)He(d,p)(4)He fusion reactions. These are important reactions for the big bang nucleosynthesis and the future of energy generation on Earth. Starting from a selected similarity-transformed chiral nucleon-nucleon interaction that accurately describes two-nucleon data, we performed many-body calculations that predict the S factor of both reactions. Virtual three-body breakup effects are obtained by including excited pseudostates of the deuteron in the calculation. Our results are in satisfactory agreement with experimental data and pave the way for microscopic investigations of polarization and electron-screening effects, of the (3)H(d,γn)(4)He bremsstrahlung and other reactions relevant to fusion research.