Quantum dynamics simulation of the ultrafast photoionization of Li-2

The Li-2 species offers an ideal system to compare experimental pump/probe ultrafast photoionization with quantum dynamical calculations on well chara cterized potential energy surfaces. The present work utilizes the best avai lable potential energy surfaces and appropriate quantum dynamical methods t o analyze the photoionization and dynamics of a wave packet prepared in the E (1)Sigma (+)(g) shelf state of lithium dimer. A direct comparison betwee n calculated (ab initio) and measured quantum dynamics is made for signals obtained with different laser pulse shapes, intensities, and chirps, and th e validity of the theoretical model is considered, as well as the applicabi lity and failure of perturbation theory. The results illustrate the high se nsitivity of the time-dependent pump/probe ionization transient signals to the detailed modeling of both the pump and probe stages. They also show som e of the inadequacies of the current potential surfaces and dipole moment m atrix elements of lithium dimer. (C) 2001 American Institute of Physics.