The far-infrared collision-induced spectrum of liquid and near-critical CO2

Abstract

Far-infrared (15–200 cm−1) absorption spectra of CO2 have been obtained (i) in the super-critical gas at 306 K with densities from 80 to 122 amagat, (ii) in the saturated liquid at 298, 272, and 236 K, and (iii) on the critical isochore in the temperature range 0.02 K < (T – Tc) < 2.0 K. The gas-phase measurements are in agreement with previous work, but an error in previously reported liquid-phase results is revealed. In contrast to the previous measurements of Mannik and Stryland on the ν1 band, the far-infrared spectra showed no measurable effects associated with density fluctuations in the critical region. A simple statistical theory is proposed to account for this result.