THE INDUCED SPECTRUM OF HYDROGEN IN THE CONDENSED PHASE AND ITS IMPLICATIONS FOR THE STUDY OF THE SOLID STATE OF $H_{2}$

$^{1}$ J.Van Kranendonk, ``Solid Hydrogen'', Plenum Press, New York and London, (1983). $^{2}$ C.K.N. Patel, E.T. Nelson and R.J. Kerl, Phys.Rev.Lett. 47, 1631 (1981). $^{3}$ Chien-Yu Kuo, Martha M.F. Vieira and C.K.N. Patel, Phys.Rev.Lett.49, 1284 (1982). $^{4}$ Chien-Yu Kuo, Martha M.F. Vieira, R.J. Kerl and C.K.N. Patel, Phys. Rev.Lett. 50, 256 (1983).Author Institution: Spectroscopy Division, Bhabha Atomic Research CentreMuch of our knowledge of solid $H_{2}$ has emerged from an investigation of its Raman and induced infrared $spectra^{1}$. Study of the induced spectrum of $H_{2}$ in the condensed state, which began in the late 50s, is still being pursued in various laboratories as a front line area. The very recent work of Patel and $co-workers^{2-4}$ devoted to the study of the spectrum in the regions of the first, second and third overtones has uncovered a wealth of information. A particularly interesting result is the evaluation of the transverse-optical and longitudinal-optical phonon densities in p $H_{2}$ from its infrared spectrum. The present paper aims at giving an upto date review of the spectroscopic work on condensed hydrogen