Transfer and storage of vibrational energy in liquids: Liquid nitrogen and its solutions with carbon monoxide

Abstract

We have produced vibrational excitation in liquid nitrogen and its solutions with carbon monoxide by flooding the samples with infrared radiation from a blackbody source. Infrared fluorescence from these excited liquids was monitored in order to investigate their relaxation kinetics and spectral profiles. For the first time the collision induced emission of excited liquid nitrogen is reported. The radiative decay of undoped nitrogen, which is a measure of the ability of the liquid to store vibrational energy, was measured to be 45±5 sec; however, fluorescence could be detected for over 2 min. New relaxation channels are opened for excited N2 when CO is added and the lifetimes are shorter. These relaxation channels were investigated in detail. The radiative lifetime of excited CO in liquid nitrogen was determined. We were also able to place upper limits on the V–T,R relaxation rates of excited CO and N2 in the liquid. In addition to these rate constants, a model for radiation trapping was developed which successfully mimicked the observed kinetic and spectral behavior of the liquid N2–CO system in the region where self-absorption dominates.