Transfer and storage of vibrational energy in liquids: collisional up-pumping of carbon monoxide in liquid argon

Isotopically enriched carbon monoxide (88% ¹³C¹⁶O, 12% ¹³C¹⁸O) dissolved in liquid argon was optically pumped to the $v = 1$ level by a CW CO laser. This energy was then redistributed by collisional up-pumping to higher vibrational levels. Fluorescence from vibrational levels up to $v = 20$ of the heavier isotope was observed from the steady-state distribution. The features of the population distribution are discussed in terms of the strength of optical pumping, carbon monoxide concentration, translational temperature, and the pertinent rate constants for energy transfer. For some conditions the populations of the vibrational levels are inverted. The potential for these solutions to store vibrational energy is discussed.