Dashevskaya E I, Litvin I, Nikitin E E, Troe J
Department of Chemistry, Technion-Israel Institute of Technology, Haifa 32000, Israel.
J Chem Phys. 2006 Oct 21;125(15):154315. doi: 10.1063/1.2357951.
A semiclassical version of the quantum coupled-states approximation for the vibrational relaxation of diatomic molecules in collisions with monatomic bath gases is presented. It is based on the effective mass approximation and a recovery of the semiclassical Landau exponent from the classical Landau-Teller collision time. For an interaction with small anisotropy, the Landau exponent includes first order corrections with respect to the orientational dependence of the collision time and the effective mass. The relaxation N(2)(v=1)-->N(2)(v=0) in He is discussed as an example. Employing the available vibrationally elastic potential, the semiclassical approach describes the temperature dependence of the rate constant k(10)(T) over seven orders of magnitude across the temperature range of 70-3000 K in agreement with experimental data and quantum coupled-states calculations. For this system, the hierarchy of corrections to the Landau-Teller conventional treatment in the order of importance is the following: quantum effects in the energy release, dynamical contributions of the rotation of N(2) to the vibrational transition, and deviations of the interaction potential from a purely repulsive form. The described treatment provides significant simplifications over complete coupled-states calculations such that applications to more complex situations appear promising.
本文提出了一种半经典版本的量子耦合态近似方法，用于描述双原子分子与单原子浴气碰撞时的振动弛豫。该方法基于有效质量近似，并从经典的朗道 - 泰勒碰撞时间恢复半经典朗道指数。对于具有小各向异性的相互作用，朗道指数包括碰撞时间和有效质量的取向依赖性的一阶修正。以He中N₂(v = 1)→N₂(v = 0)的弛豫为例进行了讨论。利用现有的振动弹性势，半经典方法描述了速率常数k₁₀(T)在70 - 3000 K温度范围内七个数量级的温度依赖性，与实验数据和量子耦合态计算结果一致。对于该系统，按重要性顺序对朗道 - 泰勒传统处理的修正层次如下：能量释放中的量子效应、N₂旋转对振动跃迁的动力学贡献以及相互作用势与纯排斥形式的偏差。所描述的处理方法比完整的耦合态计算有显著简化，因此在更复杂情况下的应用前景广阔。
