Knowledge Bank

Experimental values of the integrated intensity of the zero-phonon $R2(0)$ and $R3(0)$ transitions in solid HD are reported for the first time. Three distinct dipole components, the allowed dipole and the shifted isotropic and anisotropic overlap induced-dipoles, in conjunction with their associated interferences, all play an important role in the absorption process. A two-parameter model describing the dependence of the induced dipoles on the internuclear separation is constructed. The parameters in this model are then determined by fitting to the previously observed $R1(0)$ and the newly measured $R2(0)$ intensities. The $R3(0)$ transition intensity predicted by our model agrees well with the experimental value, and the present model also enables us to refine the theoretical calculation of the intensity of the $RO(0)$ transition published previously.