Abstract: Precise Raman measurements of high-density [sup 4]He have been made possible by improvements in high-pressure light scattering techniques. Raman spectra from hcp crystals with molar volumes of 7.74 and 9.06 cm[sup 3], representing compressions of ”= (approximately-equal-to) 60% from crystals at the lowest possible density, help to determine the applicability of conventional lattice dynamics to solid helium at high pressure. Temperature-dependent anharmonic effects were quantitatively observed for the first time and are interpreted in terms of specific phonon interactions.

Rct Date:(Received 26 December 1984)
PACS:Type: E-Experimental. Format L-Letter. Year: 85. Class nos. 67.80.Cx; 78.30.Gt
Country:US-United States
CPM no.: Microfilm no(s): 8504C2415 Abstract no(s): 2.05718
Keywords:Number: 07. ANHARMONICITY; TEMPERATURE DEPENDENCE; LATTICE DYNAMICS :Q1; PHONONS; SOLID HELIUM 4 :T1; RAMAN SPECTRA :Q1; VERY HIGH PRESSURE