VARIATION OF THE RAMAN SPECTRUM OF SOLID HYDROGEN WITH ORTHO–PARA RATIO

Abstract

The frequencies and shapes of the vibrational Raman lines, Q 1 (0) and Q 1 (1), of solid hydrogen at 2.1 °K have been studied for a series of ortho–para ratios, c o /c p . In the concentration range 0.75 > c o > 0.20 and 1.0 > c p > 0.25, each Q line has a single maximum, and can be interpreted in terms of traveling vibrational excitations. For c o < 0.20 the Q 1 (1) line splits into a band of closely spaced lines; at these low concentrations traveling ortho excitations apparently cannot be sustained, and the components of the Q 1 (1) line represent various nearest-neighbor couplings of ortho molecules. Some observations on the S 1 (0) line were also made.