Observation of the high-resolution infrared absorption spectrum of CO2 molecules isolated in solid parahydrogen

Abstract

We report the observation of high-resolution (0.008 cm−1) infrared absorption spectra of CO2 molecules isolated in solid parahydrogen (pH2) matrices at T=2.4 to 4.8 K. Several extremely sharp (0.01 to 0.04 cm−1 full-width-at-half-maximum) absorption features appear in the 2343.5 to 2345 cm−1 region. We assign the three strongest peaks to the v3 mode of isolated CO2 molecules. The spectra are consistent with trapping of the CO2 molecules in three distinct double-substitutional sites in hcp and fcc regions of the pH2 solid. We offer several hypotheses as to the origins of the numerous weaker absorption features.