Low temperature fluorescence studies of the deactivation of the bend-stretch manifold of CO2

Laser fluorescence has been used to measure rate constants for the vibrational deactivation of the bend-stretch manifold of CO2 between 300 and 170 K. The technique employed a pulsed chemical CO laser to produce vibrationally excited CO. This was used in a collisional pumping scheme designed to deposit an excess of vibrational energy in the bend-stretch manifold of CO2. The deactivation of this vibrational manifold has been studied using the following collisional partners: CO2, Ar, Xe, N2 and H2. Our results are compared with the limited amount of other low temperature data which have been published and with data obtained using a shock tube in the temperature range of about 1000 to 400 K. The present low temperature and the published high temperature results extrapolate together smoothly and clearly show the large deviations from Landau-Teller behaviour which occur at low temperatures. (orig.)