Collisional removal of CH2(1A1): Absolute rate constants for atomic and molecular collisional partners at 295 K

The technique of cw laser resonance absorption has been used to monitor the time evolution of individual CH2(1A1) rotational levels following the excimer laser photolysis of CH2CO. Absolute rate constants for the removal of CH2(1A1) by He, Ar, Kr, N2, CO, O2, CH4, C2H6, C3H8, C2H4, i-C4H8, and CH2CO have been determined at 295 K. Removal efficiencies range from nearly gas-kinetic for the higher hydrocarbons and CH2CO to 10−2 for He. For He, Ar, and CH2CO removal rates were measured for the v2=1 excited bending vibrational level and found to be identical to the ground state rates. Pseudo-first-order rate constants for equilibration of the nascent rotational distribution in collisions with He and CH2CO were found to be factors of 17 and 2.7 faster than the respective removal rates.