2-PHONON RAMAN-SCATTERING OF HCP SOLID HE-4

Raman spectra of hcp solid He-4 have been measured at a temperature of 0.71 K and at a molar volume of 20.98 cm3/mol. The spectra measured w ith an instrumental resolution of 1.1 cm-1 show the feature: a sharp o ne-phonon peak is observed at 7.39 +/- 0.06 phonon peak is observed at 7.39 +/- 0.06 cm-1, the two-phonon spectrum appears in the energy reg ion about 10-45 cm-1, and a broad continuous tail extends to energy sh ifts higher than the two-phonon region. A newly found fact is that fou r peaks have been resolved in two-phonon spectra at 17.1, 20.9, 25.2, and about 30 cm-1. The two-phonon spectral structure has good qualitat ive similarity to that calculated by theoretical works.