Nuclear-spin conversion analysis of nu(2) + nu(4) combination band of crystalline methane in phase II

摘要

We conducted reflection-absorption infrared spectroscopy in an ultrahigh vacuum and observed the nu (2) + nu (4) combination band of crystalline methane in phase II, where the rotating and librating species coexist. We analyzed the time- and temperature-dependence of the spectrum due to the nuclear-spin conversion of methane to update the assignment of the rotational and librational structure of this band. The conversion analysis performed in the present work will also be applicable to the detailed assignments of overtones and other combination bands.