Electronic structure of LiH and NaH

Self-consistent Hartree-Fock energy bands are constructed for LiH and NaH. These energy bands are corrected for effects of correlation and relaxation. The case of NaH is of particular interest in that the valence bandwidth is greater than the excitation energy of a longitudinal exciton. This causes singularities to appear in the simpler electronic polaron models used to include correlation effects. The need to use degenerate perturbation theory for certain regions of the bands is emphasized as the only complete solution to the problem. The position of the $n=1\mathrm{}$ exciton line for valence and core excitations is computed using the one-band one-site model in conjunction with the proper $\hat{O}\hat{A}\hat{O}$ operator.