惰性气体氦、氖、氩原子与氢(氘、氚)分子碰撞截面的理论计算

原子分子相互作用在许多物理过程中都十分重要.原子分子碰撞过程中转动激发截面的研究是确定原子与分子间相互作用的理想方法,许多理论和实验工作者在这方面做了大量工作,并得到理论和实验数据.本文用密耦近似计算了惰性气体He、Ne、Kr与h2、D2、T2碰撞的弹性和转动激发截面,原子入射能量分别为0.05 eV、0.15eV、0.20eV和0.25eV.     

ANGULAR DISTRIBUTION OF INELASTIC COLLISIONS BETWEEN HELIUM AND H 2

１ＦＯＲＭＵＬＡＴＩＯＮＷｅａｓｕｍｅｔｈｅｅｌｅｃｔｒｏｎｉｃｍｏｔｉｏｎｈａｓｂｅｅｎｓｅｐａｒａｔｅｄｏｕｔｂｙｔｈｅＢｏｒｎＯｐｐｅｎｈｅｉｍｅｒａｐｐｒｏｘｉｍａｔｉｏｎ．Ｃｏｎｔｒｉｂｕｔｉｏｎｓｏｆｅｌｅｃｔｒｏｎｉｃａｎｇｕｌａｒｍ...     

低能氖原子与H2(D2、T2)分子碰撞微分截面的研究

用密耦方法及Tang-Toennies势模型计算了Ne-H2(D2、T2)碰撞体系的转动激发碰撞截面,得到了H2分子的对称同位素替代情形下Ne-H2(D2、T2)三碰撞体系总截面及微分截面的变化规律.     

Rb(7S-5D)-H2,He能量转移截面与温度的关系

脉冲激光双光子激发Rb(5S)态到Rb(5D)或Rb(7S)态,在样品池条件下,利用原子荧光光谱方法测量了Rb(7S-5D)-H2,He碰撞能量转移截面与池温的关系.利用三能级模型的速率方程分析.通过测量在不同H2或He密度下的直接荧光与转移荧光的时间积分强度比,在353～493 K温度范围内得到了Rb(7S-5D)-H2,He的反应与非反应碰撞能量转移截面.对于Rb(7S)+H2→Rb(5D)+H2,其转移截面随温度的增加而减小,而其逆过程的转移截面则随温度的增加而增加.对于与He的碰撞,在不同温度下7S-5D的转移截面均符合细致平衡原理,7S,5D态与H2的碰撞速率系数是反应与非反应速率系数之和,利用实验数据可以分别确定反应与非反应截面,7S态的平均反应截面与5D态平均反应截面之比约为1.5.Rb(7S)与H2的反应活动性大于Rb(5D).     

He^＋＋H^—和Li^＋＋D^—碰撞的电荷转移截面计算

用多通道Ｌａｎｄａｕ－Ｚｅｎｅｒ方法计算了Ｈｅ＋＋Ｈ－和Ｌｉ＋＋Ｄ－低能碰撞过程中电荷转移截面，碰撞体系的初态与末态间的耦合矩阵元由渐近方法得到。计算结果与最近的实验结果进行了比较     

基态S和D原子的低能弹性碰撞及SD(X~2Ⅱ)自由基的准确相互作用势与分子常数

使用Gaussian03程序包提供的CCSD(T)理论及Duning等的相关一致基cc-pVnz和aug-cc-pVnZ(n=2,3,4,5),对SD(X~2Ⅱ)自由基的平衡核间距、谐振频率及相互作用势进行了计算,并拟合出了相应的光谱常数.在CCSD(T)/aug-cc-pV5Z理论水平下,光谱常数D_0,D_e,D_e,R_e,ω_e.a_e,B_o及B_e的值分别为3.65730 eV,3.77669 eV,0.13424 cm~(-1),1938.372 cm~(-1),0.09919 cm~(-1),4.88585 cm~(-1)和4.8872 cm~(-1),均与已有的实验结果相符很好.利用在CCSD(T)/aug-cc-pv5Z理论水平下获得的相互作用势,在绝热近似下通过数值求解双原子分子核运动的径向薛定谔方程,找到了J=0时SD(X~2Ⅱ)自由基的全部23个振动态,完整地求出了每一振动态的振动能级及相应的经典转折点、惯性转动常数和离心畸变常数;在1.0×10~(-11)-1.0×10~(-4)a.u.的碰撞能区内通过数值求解原子.原子散射的径向薛定谔方程,研究了基态S原子和基态D原子沿sD(X~2Ⅱ)相互作用势的弹性碰撞,计算了这一弹性碰撞的总截面和各分波截面,分析了各分波截面对总截面的影响.结果表明:总截面的形状主要由S分波截面决定,尽管直到l=4的各分波截面均有形状共振存在,但由于其强度都较弱,全部被湮没在较强的总弹性截面中.

Abstract：

The equilibrium internuclear separations, harmonic frequencies and interaction potentials have been calculated by employing the CCSD(T) theory in combination with the series of the correlation-consistent basis sets, cc-pVnZ and aug-ce-pVnZ (n = 2, 3, 4, 5), of Dunning and co-workers. The potential energy curves are all fitted to the Murrell-Sorbie functions, which are used to determine the spectroscopic parameters. At the CCSD(T)/aug-cc-pV5Z level of theory, the values of D_0, D_e, R_e, w_e, a_e,B_0 are 3.65730 eV, 3.77669 eV, 0.13424 cm~(-1), 1938.372 cm~(-1), 0.09919 cm~(-1) , 4.88585 cm~(-1) and 4.8872 cm~(-1), respectively, which conform almost perfectly with the available measurements. With the analytic interaction potential obtained at the CCSD(T)/aug-cc-pV5Z level of theory, a total of 23 vibrational states has been predicted for the first time when the rotational quantum number J is set to equal zero (J = 0) by solving the radial Schrodinger equation of nuclear motion. The complete vibrational levels, classical turning points, inertial rotation and centrifugal distortion constants are reproduced from the SD (X~2Ⅱ) potential when J = 0. The total and various partial-wave cross sections are calculated for the elastic collisions between the ground-state S 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 SD(X~2Ⅱ) interaction potential. No shape resonances can be found in the total elastic cross sections. 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 various partial waves, they are all covered up by the strong total elastic cross sections.     

Rotational inelastic scattering of Li-N2 and Li-CO systems

A non-perturbative approach to rotationally inelastic scattering is discussed. The method is applicable regardless of the magnitude of the coupling strength for a certain class of potential functions if the energy transfer is either small or equal to zero. Various cross sections for rotational transition (0 → 2) are calculated for Li-N₂ and Li-CO systems with an assumption that the diatomic molecules are rigid. With reasonable choice of potential parameters, the calculated elastic differential cross sections agree well with the available experimental results. The inelastic differential cross sections are found peaked in the backward hemisphere for both systems.     

采用量子波包方法和准经典轨线方法研究S(~3P)+HD反应

利用量子波包方法和准经典轨线方法在一个新的3A′′势能面上研究了S(3P)+HD→SD+H和SH+D反应的动力学性质.计算得到了两个反应通道在碰撞能为0.8—2.2 eV范围内的J=0反应几率、积分反应截面、内同位素因子和产物转动取向因子.这些结果揭示了S(3P)+HD反应非常明显的内同位素效应.通过对势能面和反应轨线的分析,我们发现了SD+H反应通道一个新的反应机制.S(3P)+HD反应的内同位素效应可以利用新发现的反应机制和反应的质量组合来进行解释.     

He与HD、HT、DT碰撞的转动激发研究

采用Tang-Toennies势模型,通过坐标变换,得到了氦原子与氢的非对称同位素替代分子体系在质心坐标系中的势能函数.在此基础上,计算了上述体系的低能碰撞转动激发截面.文中最后讨论了氦原子与氢的非对称同位素替代体系碰撞的微分截面的变化规律     

闭通道对氦氢碰撞激发分波截面影响的研究

采用精确度较高的密耦近似方法计算了不同能量下的氯原子与氢分子碰撞体系的振转激发分波截面.在计算时依次考虑了入射通道中耦合态的数目为开通道数加上1个闭通道数,2个闭通道数,3个闭通道数,直到7个闭通道数的情况.结果表明:在研究氦氢碰撞体系的弹性碰撞、纯转动激发时,可以只考虑1个闭通道的影响,但在研究振转激发分波截面时,至少要考虑5个闭通道,才能得到比较准确的计算结果.     

Close coupling calculations for excitation partial cross sections in Ne--HF collisions

This paper reports that an exact quantum close coupling calculation is carried out for rotational excitation in Ne HF collisions on the available anisotropic potential. Partial cross sections are obtained separately at the incident energies of 48.35, 75, 120 and 150meV. The reliability of the results is demonstrated by comparison with previously published theoretical findings. Based on the calculations, the effect of the potential energy surface on the excitation partial cross sections is discussed in detail.     

Quantum stereodynamics study for the reaction F + HD

This paper studies the quantum stereodynamics of the F + HD(υ = 0, j = 0) → HD + F/HF + D reaction at the collision energies of 0.52 and 0.87~kcal/mol. The quantum scattering calculations, based on Stark-Werner potential energy surfaces, show that the differential cross sections for the HF(υ' = 2) + D and DF(υ' = 3) + H channels are consistent with the recent theoretical results. Furthermore, the product rotational angular momentum orientation and alignment have been determined for some selected rovibrational states of the HF + D and DF + H channels.     

Quantum calculations of rotational and NMR relaxation,depolarized Rayleigh and rotational Raman line shapes for H2(HD)−He mixtures

The two ab initio vibrotor potentials of H₂?He previously published by Meyer, Hariharan, and Kutzelnigg have been composed in one potential grid. After using this potential in close coupled scattering calculations we have subsequently obtained rotational relaxation cross sections for para- and ortho-H₂, NMR relaxation times for ortho-H₂, depolarized Rayleigh line broadening cross sections for para-, ortho-, and normal-H₂, and rotational Raman line width and shift cross sections for S₀(0), S₀(2) transitions, at temperatures between 20 and 450 K. The agreement with previous and more recent measurements has been found completely satisfying, with the exception of the rotational relaxation cross sections of para-H₂. Throughout the paper previous results derived from the multiple property fit of Shafer and Gordon have been included for comparison. The new ab initio potential is obviously better, except for the rotational relaxation cross sections. The interaction potential of HD?He transformed from the new H₂?He potential is also presented in this paper. It has been used recently in a very successful application of the Waldmann-Snider kinetic theory describing transport, relaxation, and reorientation phenomena in magnetic fields. Therefore, only the rotational relaxation cross sections, converged up to about 400 K, have been presented in this paper.     

Some Observations about the MOLSCAT

For calculation of cross sections for collisional transitions between rotational levels in a molecule,a computer code,MOLSCAT is available.For the transitions between rotational levels in H_2 CS due to collisions with He atom,we have calculated cross sections under the CS approximation,for example,for total energy 11 cm~(-1).The calculations have been done for the single energy 11 cm"1 and for ten combinations.We have found that the cross sections for the single energy 11 cm~(-1),differ from those in the first seven combinations,but are in agreement with those in the last three combinations.The reason for the difference in the results appears that the MOLSCAT uses the intermediate data of calculations for one energy,in the calculations for other energies.The agreement with the last three combinations may be understood that when the energy of combination is in the decreasing trend,the cross sections for the first(common)energy are equal.It may be suggested to run the MOLSCAT for a single energy at a time.     

Positive parity states in Er

The positive parity states in ¹⁶⁷Er are described in terms of the rotational model, where the particle-rotation coupling is taken into account. The moment of inertia, the Fermi energy and the coupling strength are determined by fitting the energies. The wave functions thus obtained are used to calculate the (d, p) stripping and (d, t) pick-up cross sections and branching ratios. The results obtained are in agreement with experimental data.     

Magnetic trapping and Zeeman relaxation of NH (X3Sigma-)

NH radicals are magnetically trapped and their Zeeman relaxation and energy transport collision cross sections with helium are measured. Continuous buffer-gas loading of the trap is direct from a room-temperature molecular beam. The Zeeman relaxation (inelastic) cross section of magnetically trapped electronic, vibrational, and rotational ground state NH molecules in collisions with 3He is measured to be 3.8+/-1.1 x 10(-19) cm(2) at 710 mK. The NH-He energy transport cross section is also measured, indicating a ratio of diffusive to inelastic cross sections of gamma=7 x 10(4), in agreement with recent theory [R. V. Krems, H. R. Sadeghpour, A. Dalgarno, D. Zgid, J. K?os, and G. Cha?asiński, Phys. Rev. A 68, 051401 (2003)10.1103/PhysRevA.68.051401].     

Isotope effect and Coriolis coupling effect forthe Li + H(D)Cl → LiCl + H(D) reaction

A time-dependent quantum wave packet method is used to investigate the dynamics of the Li + H(D)Cl reaction based on a new potential energy surface(J. Chem. Phys. 146 164305(2017)). The reaction probabilities of the Coriolis coupled(CC) and centrifugal sudden(CS) calculations, the integral cross sections, the reaction rate constants are obtained. The rate constants of the Li + HCl reaction are within the error bounds at low temperature. A comparison of the CC and CS results reveals that the Coriolis coupling plays an important role in the Li + H(D)Cl reaction. The CC cross sections are larger than the CS results within the entire energy range, demonstrating that the Coriolis coupling effect can more effectively promote the Li + DCl reaction than the Li + HCl reaction. It is found that the isotope effect has a great influence on the title reaction.     

基于Ne-HBr从头算CCSD(T)势的散射截面

利用非线性最小二乘法拟合在CCSD(T)/aug-cc-pVQZ理论水平下计算的相互作用能,得到了基态Ne-HBr复合物相互作用势的解析表达式.基于拟合的从头算CCSD(T)势,通过收敛的密耦计算得到了入射能量分别为40,60,80和100 meV时,Ne-HBr散射的微分截面和分波截面,详细讨论了态-态转动激发截面对总非弹性散射截面的影响和散射截面随能量的变化趋势.希望研究结果对该体系的散射实验和进一步的理论研究能提供参考信息.     

准经典轨线法研究交换反应H(D)+SH/SD的动力学性质

硫在氢气中的燃烧反应在气象化学、燃烧反应和大气污染中都扮演着重要的角色, 近年来一直受到广泛关注, 其逆反应也渐渐成为人们的研究对象. 以Lü 等得到的精确势能面(Lü S J, Zhang P Y, Han K L, He G Z 2012 J. Chem. Phys. 136 94308) 为基础, 用准经典轨线法对交换反应H(D)+SH/SD的动力学性质进行了研究. 计算了包括反应截面、速率常数、不透明函数、产物振动和转动分布等在内 的标量性质和包括产物散射方向、转动角动量定向和取向性质在内的矢量性质. 详细分析了碰撞能量和同位素效应对反应H(D)+SH/SD 的动力学性质的影响. 结果表明, 随着碰撞能量的增加, 反应截面逐渐增大, 产物的后向散射逐渐减弱, 产物转动角动量的取向和定向性质逐渐增强; 另外, 同位素效应对反应的动力学性质也有明显的影响. 以反应动力学性质和势能面为基础, 详细讨论了反应H(D)+SH/SD 的反应机制. 关键词： 准经典轨线 反应截面 速率常数 振动-转动分布