Phonons of solid phases (α, β, δ, ε) of carbon monoxide by optical studies

Abstract

The phase diagram of solid carbon monoxide was investigated in the pressure range 0–10 GPa and temperature range 30–300 K by infrared and Raman spectroscopy. The tentative phase diagram known from literature was expanded and specified in details. The δ-phase region is divided into two subphases — δrot and δloc that is similar to the one in solid nitrogen. The pressure-temperature behavior of the elementary and combined excitations was also followed up. The vibron overtone region was carefully investigated by FTIR spectroscopy as a function of temperature at different pressures, whereas the fundamental one — by Raman spectroscopy. The features of the IR-active phonon sideband to the vibron overtone were investigated in details in the whole pressure-temperature region. The lattice-phonon spectra were studied by Raman spectroscopy as a function of pressure (at lowest temperature) and by IR spectroscopy as a function of temperature at saturated vapor pressure.