Mixed vibrational and rotational excitations in liquid and solid para-hydrogen

Mixing of molecular states, in dense liquid and solid hydrogen, can give useful information on certain components of the microscopic molecular dynamics. However, since no quantum dynamic theory exists yet,the comparison can be exploited only to the level of the static quantities (integrated intensities). In this case a relevant role is played by the anisotropic components of the intermolecular potential. Since double transitions are induced by pair interactions, a purely pair theory can be applied, even in the condensed phases. The experiments were concentrated on the double rotational transition S-0(0)+S-0(0) and the double rotovibrational transition Q(1)(0)+S-0(0), and were carried out as a function of density in order to test a relatively wide range of intermolecular distances.