Crystal field theory analysis of rovibrational spectra of carbon monoxide monomers isolated in solid parahydrogen

We report the first rotationally resolved and completely assigned rovibrational spectrum for a nonhydride molecule rotating in the solid phase: carbon monoxide (CO) monomers isolated in cryogenic solid parahydrogen (p-H(2)). We employ a modified crystal field theory model, in which the CO molecular spectroscopic constants are taken as adjustable parameters, to make good spectroscopic assignments for all the observed features. We discuss the limitations of this approach and highlight the need for improved theoretical models of molecular rotation dynamics in quantum solids.