激发态Li原子和基态Ar原子的相互作用势及低能弹性碰撞

摘要

在MRCI+Q/ang-cc-PCVQZ+DK理论基础上对LiAr第一激发态(A2Π)的势能曲线进行了理论计算,采用HFD(Hartree-Fock dispersion)解析势能函数对得到的势能曲线进行拟合,并得到了相应的光谱常数,计算结果与实验值和大部分理论计算值符合得很好.通过求解核运动的薛定谔方程完整地获得了每个电子态下J =0时的振动能级Ev、转动惯量Bv和6个离心畸变常数(Dv , Hv , Lv , Mv , Nv , Ov ).然后采用分波法研究了低温及极低温度下激发态Li原子和基态Ar原子沿LiAr相互作用势的弹性碰撞,在1.0×10−12—3.45×10−6 eV碰撞能区内通过数值计算得到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截面的影响.结果表明：在入射能量低于10−9 eV时弹性散射的总截面值很大且几乎为一常数,总弹性截面的形状主要由s分波决定,但是随着碰撞能量的增加,s分波对总截面的贡献不断减少,高阶分波对散射截面的贡献逐渐增大.%The potential energy curve (PEC) for the first excited state (A2Π) of LiAr is calculated using the multireference configuration interaction method in combination with the basis set, ang-cc-PCVQZ. The Davidson correlation (+Q) and the scalar relativistic effect (+DK) are taken into account in the calculations. And PEC is fitted to analytical Hartree-Fock-dispersion potential function, thereby determining the spectroscopic parameters. These obtained parameters are in excellent agreement with the available experimental and theoretical values. By solving the radial Schrödinger equation of nuclear motion, the vibration levels, rotary inertia and six centrifugal distortion constants (Dv , Hv , Lv , Mv , Nv , Ov) are obtained for the first time. The elastic collisions between the excited-state Li and the ground-state Ar atoms are investigated at low and ultralow temperatures when the two atoms approach to each other along the LiAr (A2Π) interaction potential. The total and various partial-wave cross sections are calculated at energies from 1.0 × 10−12 to 1.0 × 10−3 eV by numerical calculation. The effect of each partial-wave cross section on the total elastic cross section is discussed carefully. The results show that the total elastic cross section is very large and almost constant at ultralow temperatures, and its shape is mainly dominated by the s-partial wave. But with the increase of collision energy, contribution of s-partial wave to the total cross section decreases and the contribution of higher-order partial wave to scattering cross section increases gradually.