MQCT. I. Inelastic Scattering of Two Asymmetric-Top Rotors with Application to H2O + H2O
MQCT. I. Inelastic Scattering of Two Asymmetric-Top Rotors with Application to H2O + H2O
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DOI：
10.1021/acs.jpca.7b03554
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发表时间：
2017-07-06
影响因子：
2.9
通讯作者：
Babikov, Dmitri
中科院分区：
文献类型：
--
作者：
Semenov, Alexander;Babikov, Dmitri
建立了两个不对称顶转子分子非弹性碰撞的混合量子/经典理论。在这种方法中，分子（内部）的旋转状态之间的量子态到态转换使用依赖于时间的薛定谔方程进行量子力学处理，而它们的相对平移运动（负责散射）则使用平均轨迹方法进行经典处理。提出了过渡矩阵元素公式的两种版本：一种直接的方法是在所有内部自由度上使用数值多维正交，另一种更标准的分析方法是在球谐基集上使用PES展开。提出了对相同分子散射情况的适应，并将其应用于两个水分子H2O + H2O的旋转激发，使用最新文献中的PES。在较宽的能量范围内，计算了从系统基态到若干低洼激发态的碰撞激发。计算的不透明度函数分析显示了一个相当不寻常的散射机制，主要是由一个强各向异性的远程相互作用（偶极子-偶极子）。对耦合状态（CS）近似进行了测试，发现与该方法的完全耦合版本在半定量上（在2因子范围内）一致。弹性散射的微分截面显示一个非常窄的正向散射峰。
A mixed quantum/classical theory (MQCT) for the inelastic collision of two asymmetric-top rotor molecules is developed. In this method, the quantum state-to-state transitions between the rotational states of molecules (internal) are treated quantum mechanically using the time-dependent Schrodinger equation, whereas their relative translational motion (responsible for scattering) is treated classically, using the average trajectory approach. Two versions of the formula for transition matrix elements are presented: a straightforward approach that uses numerical multidimensional quadrature over all the internal degrees of freedom and a more standard analytic approach that uses the expansion of the PES over the basis set of spherical harmonics. Adaptation to the case of identical molecules scattering is presented and is applied to the rotational excitation of two water molecules, H2O + H2O, using the PES from recent literature. Calculations of collisional excitation from the ground state of the system into a number of low-lying excited rotational states are carried Out in a broad range of energies. Analysis of computed opacity functions shows a rather unusual scattering regime, dominated by a strong anisotropic long-range interaction (dipole-dipole). The coupled-states (CS) approximation is tested and found to agree semiquantitatively (within a factor of 2) with the fully coupled version of the method. Differential cross sections for the elastic scattering indicate a very narrow forward scattering peak.