A case study on LiH molecule

To investigate possible detection of the history of sequential transitions between electronic states by a pulse train with time-resolved femtosecond photoelectron spectroscopy, we compute the quantum wavepacket dynamics of the LiH system. The LiH system is suited for our purpose of studying time evolution of electronic interaction in that (1) the lowest excited state 

Chemical Theory Beyond the Born-Oppenheimer Paradigm 

and C states belong to the E+ irreducible representation and the B state belong to the 11 irreducible representation. The energy differences between the B and A states and between C and B states are about 1 eV, suggesting an external field of that energy linearly polarized perpendicular to the bond axis should couple the excited states. We include up to the C state (and the cation ground state) in the wavepacket dynamics 

In the present study, which is a semi-model or semi-realistic study dedicated to a survey on the pure effects of pulse trains on the photoionization spectrum, we will forego the computation of the much more expensive to compute photoelectron angular distributions, and neglect the dependence on the spatial coordinates 6k and (f k altogether. All the neutral states are taken to be coupled to the ion state in the form fi = [see 

67) and (3.68)], where, for lack of extensive calculation of the photoionization coupling matrix elements, we take for ionization /it the same constant (/x = 1) for all states. Although dependence on the molecular geometry and photoelectron momentum as well as on the neutral state to be ionized is important in obtaining detailed features of the photoelectron spectrum reflecting the dynamics of the system, our previous experience justifies the use of the simplified model for qualitative features of the photoelectron kinetic energy distribution [13, 18]. 

---