Absorption spectra of solid para- and normal hydrogen in the first overtone region

Solid hydrogen crystals of both para and normal species were grown in a glass cell 6.4 cm long and 1.0 cm in diameter using liquid-helium cryogenics apparatus. Their infrared-absorption spectra were recorded in the first overtone region 8000–9400 ${\mathrm{cm}}^{\mathrm{-}1}$. The absolute intensities of several zero-phonon transitions of the type $Q_2$(J), $Q_1$(J)+$Q_1$(J), $S_2$(J), $Q_2$(J)+$S_0$(J), $Q_1$(J)+$S_1$(J), $S_2$(J)+$S_0$(J), and $S_1$(J)+$S_1$(J) and those of the accompanying phonon branches $Q_R$ and $S_R$ were measured. The observed spectra clearly demonstrate that there is no contribution to the intensity of the pure overtone $Q_R$ phonon branch from isotropic electron overlap induction mechanism. This is in striking contrast to the observations in the fundamental band of either solid [H. P. Gush, W. F. J. Hare, E. J. Allin, and H. L. Welsh, Can. J. Phys. 38, 176 (1960)] or gaseous [S. P. Reddy, G. Varghese, and R. D. G. Prasad, Phys. Rev. A 15, 975 (1977)] hydrogen.