Deactivation of Vibrationally Excited Carbon Dioxide (ν3) by Collisions with Carbon Dioxide or with Nitrogen

Abstract

The rate constants associated with the deactivation of vibrationally excited CO2*(ν3) by collision with either CO2 or N2 have been experimentally determined from 300°–1000°K by a laser fluorescence method. The reactions investigated were CO2*(ν3)+N2⇆ lim k−5k5CO2+N2*, CO2*(ν3)+N2→ lim k5CO2*(ν1, ν2)+N2, CO2(ν3)+CO2→ lim k1CO2*(ν1, ν2)+CO2, N2*+CO2→ lim k7CO2*(ν1, ν2)+N2, where the asterisk denotes a vibrationally excited molecule, and the quantities in parentheses represent the specific excited modes of CO2. The rate constant k5 varies with temperature T (°K) as 8.60 × 107 / T3/2torr−1·sec−1. From 400°–1000°K the rate constant k1 (per torr−1 ·second−1) varies with temperature as log10k1 = A − BT−1 / 3 with A = 6.79 and B = 30.8. From 300°–400°K the measured values of k1 are greater than those corresponding to the above relation. The rate constant k6 increases from a value of 110 torr−1·sec−1 at room temperature to a value of 2700 torr−1·sec−1 at 1000°K, but the variation of k6 with temperature cannot be simply expressed. The rate constant k7 was found to be negligibly small compared to the other rate constants.