Collision-Induced infrared absorption and Raman scattering of H2 in supercritical CO2

In this study, the solvation of H2 in supercritical CO2 was investigated by co-localized infrared absorption/Raman scattering spectroscopies. The Fermi dyad and combinations of vibrational modes of CO2 were detected by Raman and infrared spectroscopy respectively, with increasing intensities according to CO2 concentrations varying from 1 to 15 mol.L-1. H2 rotational bands and vibrons with almost constant intensities were detected by Raman spectroscopy according to a constant H2 pressure of 3 MPa. In contrast, a collision-induced infrared band of H2 was reported for the first time in supercritical CO2 and its intensity was found to be directly proportional to the intensity of the CO2 bands. In addition, the intensities of the H2 and CO2 contributions were found to be sensitive to the local density fluctuations existing near the critical temperature of CO2 (Tc = 31 °C, Pc = 7.4 MPa).