Theoretical calculations of zero-temperature absorption spectra of Li in solid H2

Abstract

We employ variational and diffusion Monte Carlo methods to calculate the ground state properties of both pure and Li doped solid H2. The absorption spectra of Li in the H2 solid are calculated from the sampled ground state configurations and a pseudothermal semiclassical spectral line theory, based on the Franck–Condon principle for a condensed phase system. The T=0 numerical results of various thermodynamic properties of the pure and doped solid agree well with those from previous theoretical calculations. However, the Li spectra differ significantly from results of a finite temperature path integral Monte Carlo calculation [D. Scharf et al., J. Chem. Phys. 99, 9013 (1993)], which employed a different Li*–H2 potential. The differences in two calculations are extensively discussed here, and comparisons are also made with available experimental data. We demonstrate that accurate measurements of the Li absorption spectrum provide a powerful means to probe the local structures of the Li trapping sites.