Fa. Gorelli et al., High-pressure and low-temperature infrared study of solid oxygen: Evidenceof a new crystal structure, PHYS REV B, 60(9), 1999, pp. 6179-6182
Infrared spectroscopy has been applied to the study of solid oxygen at high
pressure and low temperature. An absorption line in the vibron fundamental
mode region has been observed, and its behavior with pressure measured up
to the transition to the epsilon phase. This absorption, not expected accor
ding to the symmetry of the delta phase, indicates the existence of a new c
rystal structure between 2 and 8 GPa at low temperature. The comparison of
the infrared and Raman frequency evolution with pressure is done quantitati
vely on the basis of a simple vibrational coupling model and the intermolec
ular coupling force constant is obtained. In contrast to solid hydrogen, he
re the coupling constant is positive and shows a strong dependence on the i
ntermolecular distance which can indicate that significant charge transfer
processes are already present in this low-pressure phase. [S0163-1829(99)05
533-2].