Pacheco Alexander B, Reyes Andrés, Micha David A
Quantum Theory Project, Departments of Chemistry and Physics, University of Florida, Gainesville, Florida 32611-8435, USA.
J Chem Phys. 2006 Oct 21;125(15):154313. doi: 10.1063/1.2357956.
The absorption of light during atomic collisions is treated by coupling electronic excitations, treated quantum mechanically, to the motion of the nuclei described within a short de Broglie wavelength approximation, using a density matrix approach. The time-dependent electric dipole of the system provides the intensity of light absorption in a treatment valid for transient phenomena, and the Fourier transform of time-dependent intensities gives absorption spectra that are very sensitive to details of the interaction potentials of excited diatomic states. We consider several sets of atomic expansion functions and atomic pseudopotentials, and introduce new parametrizations to provide light absorption spectra in good agreement with experimentally measured and ab initio calculated spectra. To this end, we describe the electronic excitation of the valence electron of excited alkali atoms in collisions with noble gas atoms with a procedure that combines l-dependent atomic pseudopotentials, including two- and three-body polarization terms, and a treatment of the dynamics based on the eikonal approximation of atomic motions and time-dependent molecular orbitals. We present results for the collision induced absorption spectra in the Li-He system at 720 K, which display both atomic and molecular transition intensities.
通过使用密度矩阵方法，将量子力学处理的电子激发与在短德布罗意波长近似下描述的原子核运动相耦合，来处理原子碰撞过程中的光吸收。对于瞬态现象有效的一种处理方法中，系统的含时电偶极矩给出了光吸收强度，而含时强度的傅里叶变换给出的吸收光谱对激发双原子态相互作用势的细节非常敏感。我们考虑了几组原子展开函数和原子赝势，并引入新的参数化方法以提供与实验测量光谱和从头计算光谱高度吻合的光吸收光谱。为此，我们用一种将依赖于角量子数的原子赝势（包括两体和三体极化项）与基于原子运动的程函近似和含时分子轨道的动力学处理相结合的方法，来描述激发态碱金属原子与稀有气体原子碰撞时价电子的电子激发。我们给出了720 K时Li-He系统中碰撞诱导吸收光谱的结果，该光谱同时显示了原子和分子跃迁强度。
