CO:LiCl(001)-(1X1)表面电子激发态及其随时演化

采用多体摄动理论研究CO:LiCl(001)-(1X1)表面的激发态性质、CO分子激子态随时演化及其寿命. 首先用局域密度近似的密度泛函理论计算CO分子吸附在LiCl(001)-(1X1)表面的几何结构; 随后运用GW近似研究LiCl块体、LiCl(001)-(1X1)干净表面以及CO:LiCl(001)-(1X1)表面的准粒子能带结构, 引入电子-空穴相互作用, 求解二粒子格林函数的Bethe-Salpeter方程(BS方程), 并得出其电子-空穴激发态及光学吸收谱, 将计算得到的光吸收谱与实验数据进行比较; 最后基于吸附系统CO:LiCl(001)-(1X1)的BS方程的解, 求解含时薛定谔方程得出的分子激发态的随时演化. 因衬底和吸附分子之间的耦合作用, CO分子激子态在随时演化的初始阶段呈现非常快的衰减, 其寿命仅为0.75fs. CO分子激子态的空穴大幅度地向衬底转移, 而激子态的电子仍然滞留在CO分子上.

The excited electronic state and its time evolution of CO adsorbed on LiCl(001)-(1X1)

The many-body perturbation theory is used to study the properties of excited electronic states of the CO molecule adsorbed on LiCl(001)-(1X1) surface, and further investigate the time evolution of the CO exciton state as well as the lifetime of the exciton state. At first, density-functional theory within local density approximation is used to calculate the ground state geometry of CO adsorbed on LiCl(001)-(1X1) surface. Next, the quasiparticle band structures of bulk LiCl, of the LiCl(001)-(1X1) surface, and of CO adsorbed on the surface are evaluated within the GW approximation. Moreover, by taking the electron-hole interaction into consideration, the electron-hole excitation states and their optical spectra are obtained from the solution of the Bethe-Salpeter equation within the theory of the two-particle Green function. The obtained optical spectra are compared with available experimental results. Finally, based on the solution of the BSE for the adsorbate system CO:LiCl(001)-(1X1), the time evolution of the CO exciton state is studied using the time-dependent Schr?dinger equation. At the initial stage, the CO exciton state exhibits a very fast decay due to the coupling of the adsorbate with the substrate, and the lifetime of the CO exciton state is only 0.75 fs. The electron of the molecule exciton state remains on the molecule while its hole is mostly transferred into the LiCl substrate.