ΔJ=4 infrared transitions of solid ${\mathrm{D}}_2$ and a Raman study of ${\mathrm{H}}_2$, ${\mathrm{D}}_2$, and HD in their liquid and solid phases

Infrared spectra of solid ${\mathrm{D}}_2$ are reported for the spectral regions around the $U_0$(0) and $U_{1\leftarrow 0}$(0) transitions. The measured integrated absorptions of these transitions arising from the hexadecapolar-induced dipole moment are in good agreement with theoretical calculations. Phonon branches and a double transition $Q_{1\leftarrow 0}$(0)+$U_0$(0) accompanying the transitions have been seen and identified by their frequencies. Raman spectra of ${\mathrm{H}}_2$, ${\mathrm{D}}_2$, and HD in their liquid and solid phases are also reported. A new feature of the $S_{1\to 0}$(0) transition in solid normal ${\mathrm{D}}_2$, manifested as a marked asymmetry in its high-frequency wing, is identified by its position, width, and intensity as due to double Raman transitions of the type $Q_{1\to 0}$(J)+$S_0$(0). These double Raman transitions arise from a near-resonant mixing of energy states due to quadrupole-quadrupole interaction and result in Raman emission that is comparable to the zero-phonon $S_{1\to 0}$(0) transition, in contrast to the pure rotational band where double Raman transitions $S_0$($J_1$)+$S_0$($J_2$) are several orders of magnitude weaker than the corresponding single $S_0$(J) transitions.