Extended interactions in the ε phase of oxygen

The high pressure infrared and Raman spectra for the ε phase of a series of oxygen samples, 16O2, 16O2 with 10% 18O2, and 18O2 with 6% 16O 18O, are reported. Assignments are made for the fundamental, combination, and isotope-induced features of this phase of solid oxygen based on a simple model that incorporates a pairwise interaction betweeen nearest-neighbor oxygen molecules within the molecular oxygen plane, with pairs forming extended chains. Vibrational analysis on this chain with two interaction force constants reproduces all of the features that we have observed.