Elastic scattering of two H（^2Sg） and N（^4Su） atoms at low temperatures and accurate spectroscopic parameters of NH （X^3∑^-） radical

This paper reports that the interaction potential for the X3Z- state of NH radical is constructed at the CCSD（T）/ cc-PV6Z level of theory. Using this potential, this paper calculates the spectroscopic parameters （De, Re, ωe, ωeχe, αe and Be） and their values are of 3.578eV, 0.10368nm, 3286.833cm^-1, 78.433cm^-1, 0.6469cm^-1 and 16.6735cm^-1 respectively, which are in excellent agreement with the experiments. Then the total of 14 vibrational states has been found when J=0 by solving the radial Schrodinger equation of nuclear motion. For each vibrational state, the vibrational manifolds are reported for the first time. And last, the total cross sections, s-wave, p-wave and d-wave cross sections are computed for the elastic collisions between two ground-state atoms （hydrogen and nitrogen） at low temperatures. It finds that the total elastic cross sections are dominated by s-wave scattering when the collision energy is below 10^-6a.u. The pronounced shape resonance is found at energy of 6.1 × 10^-6a.u. Calculations have shown that the shape resonance comes from the p-wave contributions.     

Molecular constants of LiCI（X^1∑＋） and elastic collisions of two ground-state Cl and Li atoms at low and ultralow temperatures

Interaction potentials for LiCI（X^1∑＋） are constructed by the highly accurate valence internally contracted multireference configuration interaction in combination with a number of large correlation-consistent basis sets, which are used to determine the spectroscopic parameters （D0, De, Re, ωe, ωeχe, Be and αe）. The potentials obtained at the basis sets, i.e., aug-cc-pV5Z-JKFI for Cl and cc-pV5Z for Li, are selected to study the elastic collision properties of Li and Cl atoms at the impact energies from 1.0 ×10^-12 to 1.0× 10-4 a.u. The derived total elastic cross sections are very large and almost constant at ultralow temperatures, and their shapes are mainly dominated by the s-partial wave at very low impact energies. Only one shape resonance can be found in the total elastic cross sections over the present collision energy regime, which is rather strong and obviously broadened by the overlap contributions of the abundant resonances coming from various partial waves. Abundant resonances exist for the elastic partial-wave cross sections until l= 22 partial waves. The vibrational manifolds of the LiCI（X^1∑＋） molecule, which are predicted at the present level of theory and the basis sets cc-pV5Z for Li and the aug-cc-pV5Z-JKFI for Cl, should achieve much high accuracy due to the employment of the large correlation-consistent basis sets.     

Investigations on molecular constants of the CD（X^2∏） radical and elastic collisions between ground-state C and D atoms at low temperatures

The potential energy curve of the CD(X~2Π) radical is obtained using the coupled-cluster singles-doublesapproximate-triples [CCSD(T)] theory in combination with the correlation-consistent quintuple basis set augmented with diffuse functions,aug-cc-pV5Z.The potential energy curve is fitted to the Murrell-Sorbie function,which is used to determine the spectroscopic parameters.The obtained D0,De,Re,ωe,ωeχe,αe and Be values are 3.4971 eV,3.6261 eV,0.11197 nm,2097.661 cm 1,34.6963 cm 1,0.2083 cm 1 and 7.7962 cm 1,respectively,which conform almost perfectly to the available measurements.With the potential obtained at the UCCSD(T)/aug-cc-pV5Z level of theory,a total of 24 vibrational states have been predicted for the first time when J = 0 by solving the radial Schr¨odinger equation of nuclear motion.The complete vibrational levels,the classical turning points,the inertial rotation constants and centrifugal distortion constants are reproduced from the CD(X~2Π) potential when J = 0,and are in excellent agreement with the available measurements.The total and the various partial-wave cross sections are calculated for the elastic collisions between the ground-state C and D atoms at energies from 1.0×10 11 to 1.0×10 4 a.u.when the two atoms approach each other along the CD(X~2Π) potential energy curve.Only one shape resonance is found in the total elastic cross sections,and the resonant energy is 8.36×10 6 a.u.The results show that the shape of the total elastic cross section is mainly dominated by the s partial wave at very low temperatures.Because of the weak shape resonances coming from higher partial waves,most of them are passed into oblivion by the strong total elastic cross sections.     

Elastic collisions between Si and D atoms at low temperatures and accurate analytic potential energy function and molecular constants of the SiD（χ^2П） radical

Interaction potential of the SiD(X2Π) radical is constructed by using the CCSD(T) theory in combination with the largest correlation-consistent quintuple basis set augmented with the diffuse functions in the valence range. Using the interaction potential, the spectroscopic parameters are accurately determined. The present D0, De, Re, ωe, αe and Be values are of 3.0956 eV, 3.1863 eV, 0.15223 nm, 1472.894 cm-1, 0.07799 cm-1 and 3.8717 cm-1, respectively, which are in excellent agreement with the measurements. A total of 26 vibrational states is predicted when J=0 by solving the radial Schro¨dinger 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 available experiments. The total and various partial-wave cross sections are calculated for the elastic collisions between Si and D atoms in their ground states at 1.0×10-11–1.0×10-3 a.u. when the two atoms approach each other along the SiD(X2Π) potential energy curve. Four shape resonances are found in the total elastic cross sections, and their resonant energies are of 1.73×10-5, 4.0×10-5, 6.45×10-5 and 5.5×10-4 a.u., respectively. Each shape resonance in the total elastic cross sections is carefully investigated. The results show that the shape of the total elastic cross sections is mainly dominated by the s partial wave at very low temperatures. Because of the weakness of the shape resonances coming from the higher partial waves, most of them are passed into oblivion by the strong s partial-wave elastic cross sections.     

The differential interference angle of ^2∏[Case（a）] diatom on rotational energy transfer in NO（X^2∏） collision with He,Ne and Ar system

To study theoretically the relationship between the differential interference angle and the scattering angle in collisional quantum interference （CQI）, we have investigated the differential interference angle of the atom-diatomic [case（a）] molecule system in detail. For the 2∏ electronic state in Hund＇s case （a）, the degree of the differential interference is also discussed. The differential interference angles of NO（X^2∏） are calculated quantitatively for the rotational energy transfer in Hund＇s case （a） induced by collision with He, Ne and Ar atoms. The method to calculate the differential interference angle is presented. Several factors that affect the differential interference angle are investigated. Finally the variation of the differential interference angle with the impact parameter and relative velocity is discussed.     

Experimental study of cross-section ratios in the collisions of Cq＋ and oq＋（q= 1-4） on atomic helium in strong-interaction region

We have measured the cross-section ratios of helium induced by C^q+ and O^q+ (q=1-4) in an energy range from 20 keV/amu to 500 keV/amu, and obtained the two-dimensional spectra by employing the coincidence method combined with the MPA-3 data acquisition system. Hence, we obtain the ratios of total single-ionization cross-sections (SI, SC, SLSI, and DLSI), total double-ionization cross-sections (DI, DC, TI, SLDI, and DLDI) and cross-sections of every process (SI, SC, SLSI, DLSI, DI, DC, TI, SLDI, and DLDI), which induce the single-ionization and double-ionization, to the total cross sections respectively. The competitive relations between the reaction-channels and the experimental data law of each reaction-channel are revealed explicitly, and the qualitative explanations involved in those results are also presented accordingly.     

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.     

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.     

Accurate calculation of the elastic scattering properties of ^7Li atoms at ultralow temperatures

The elastic scattering properties for collisions between two ^7Li atoms are investigated in the cold and ultracold regimes separately. Based on recent theoretical and experimental results, we present the improved hybrid potentials for the singlet X^1 ∑g^＋ and triplet a^3 ∑u^＋ ground states of the Li2, Our calculated values for the scattering lengths α and the effective ranges re are compared with previous ones, and found them to be in good agreement. The scattering lengths are 34.6α0 for the singlet state and -27.6α0 for the triplet state. Shape resonances occur in the collisions at low energies. We also calculate the total cross sections and the energy positions of shape resonances for both X^1 ∑g^＋ and a^3 ∑u^＋ states.     

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.     

超冷温度下钾和铯原子间弹性散射特性的精确计算

本文分别用量子方法和半经典方法计算了超冷钾和铯原子之间弹性碰撞的s波散射长度,有效力程和p波散射长度等散射参数. 超冷温度下³⁹K-¹³³Cs原子间的弹性散射截面主要为s波贡献,随着碰撞能量的增加散射截面有丰富的形状共振出现, 计算发现单重态和三重态截面分别存在显著的g波和d波形状共振.另外,本文应用简并内态近似方法获得了⁴¹K-¹³³Cs 超精细态相互作用时的s波散射长度.     

Investigation of analytical harmonic frequency and potential energy function,vibrational levels for the X^2∑^＋ and A^2Л states of CN radical

This paper calculates the equilibrium structure and the potential energy functions of the ground state （X^2∑^＋） and the low lying excited electronic state （A^2Л） of CN radical are calculated by using CASSCF method. The potential energy curves are obtained by a least square fitting to the modified Murrell-Sorbie function. On the basis of physical theory of potential energy function, harmonic frequency （ωe） and other spectroscopic constants （ωeχe, βe and αe） are calculated by employing the Rydberg-Klei-Rees method. The theoretical calculation results are in excellent agreement with the experimental and other complicated theoretical calculation data. In addition, the eigenvalues of vibrational levels have been calculated by solving the radial one-dimensional SchrSdinger equation of nuclear motion using the algebraic method based on the analytical potential energy function.     

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.     

中低速C3+与He，Ne，Ar原子相互作用过程中单电子转移绝对截面的测量

实验测量了1.7v₀—4.2v₀(v₀为玻尔速度,v₀=2.19×10⁸cm/s)的C³⁺与He,Ne,Ar原子碰撞过程中单电子转移绝对截面.将实验结果与多体经典轨道蒙特卡罗模拟计算结果做了比较,发现测量结果与多体经典轨道蒙特卡罗模拟计算结果在趋势上相符.当入射离子速度在1.7v₀—2 关键词： 离子-原子碰撞 单电子转移 绝对截面     

Cross sections of Oq+（q=1-4） electron loss in collisions with He,Ne and Ar

Electron-loss cross sections of O q+(q = 1 4) colliding with He,Ne and Ar atoms are measured in the intermediate velocity regime.The ratios of the cross sections of two-electron loss to that of one-electron loss R 21 are presented.It is shown that single-channel analysis is not sufficient to explain the results,but that projectile electron loss,electron capture by the projectile and target ionization must be considered together to interpret the experimental data.The screening and antiscreening effects can account for the threshold velocity results,but cannot explain the dependence of the ratio R 21 on velocity quantitatively.In general,the effective charge of the target atom increases with velocity increasing because the high-speed projectile ion can penetrate into the inner electronic shell of target atom.Ne and Ar atoms have similar effective charges in this velocity regime,but He atoms have smaller ones at the same velocities due to its smaller nuclear charge.