Raman Spectroscopy of Solid Hydrogen Deuteride.

A Raman spectrometer using a focused laser beam and an external resonator was designed and built to study solid hydrogen samples using Raman scattering. A number of new transitions were observed in the spectrum of solid HD, including an R_0(0) ( DeltaJ = 1) and a T_0(0) + S_0(0) (DeltaJ _1 = 3, DeltaJ _2 = 2) transition. The intensity of the latter was 4.4times 10^{ -6} relative to the allowed S_0 (0) line. These transitions occur in HD as a result of the shifted components of the induced polarizability, which arise because of the separation between the centre of mass and centre of interaction in an HD molecule. Theoretical intensity calculations of both transitions are in very good agreement with measured intensities. A U _0(0) (DeltaJ = 4) and U_0(0) + S_0 (0) transition were also observed, but calculations show that the induced polarizability makes a negligible contribution to both transitions. A feature in the vibrational (0-1) band was originally identified as R_1 (0), but disagreement between the measured and theoretical intensity and a frequency 7 cm^{-1 } higher than measured in absorption experiments led to its alternative identification as part of the Q _{rm r} phonon band. R _{rm R} phonon bands associated with the R_0(0) and R _1(0) transitions were also observed with intensities much greater than the zero-phonon lines. Two larger features in the low frequency wings of the S _0(0) and S_1(0) lines were observed and evidence was presented for the identification of these features as extensions of the R_ {rm R} phonon bands. The Raman spectrum of proton-irradiated samples of solid H _2 and D_2 were also examined with a signal-to-noise ratio as high as 10 ^5, but no new features were observed.