Figure 4
From: New high-pressure van der Waals compound Kr(H2)4 discovered in the krypton-hydrogen binary system
Raman spectrum of Kr(H2)4 at a selected pressure of 19.6 GPa; background has not been subtracted.
Roton peaks are observed in the low frequency range and two vibrons, ν1 and ν2, in the high-frequency range. The other two, much weaker vibrons, ν3 and ν4, are not observed at this pressure. The rotons and Q1(1) vibron frequency of solid H2 at the same pressure are indicated by cyan, dotted lines.
