NH_3-Ar转动激发的半经典理论计算

Semiclassical Calculation of Rotational Excitation of NH3Scattering with Ar

半经典方法以其优越于纯量子力学方法的特性特别适用于大分子散射的研究．将氨分子看作一个刚性转子，不考虑它的反演运动．体系的自由度用经典的作用量———角变量来描述，利用修正的ａｂｉｎｉｔｉｏ势在两种不同的能量条件下计算了ＮＨ３—Ａｒ散射体系转动激发的态－态跃迁的积分散射截面．计算结果与密耦合计算结果以及实验结果符合得较好，从而说明该半经典方法适用于ＮＨ３—Ａｒ散射体系．

A semiclassical approach is applied to calculating the state-to-state cross sections of rotational excitation of ammonia molecule scattering with argon atom. Semiclassical theory is more useful in the studying heavy molecular scattering. Ammonia molecule is regarded as a rigid symmetric top, and argon a structureless atom. The inversion motion of ammonia is not taken into account. It makes use of classical action-angle variables to describe the degrees of freedom of the system. The scaled ab initio potential is used, and at two different energies the computing of total cross sections are performed by using Monte-Carlo procedure. Good agreements with close coupling calculations and crossed molecular beam experiment are obtained. The semiclassical approach thus appears to be valid for ammonia-argon scattering system.