Reaction and Quenching of Cl(2P j ) Atoms in Collisions with Methane and Deuterated Methanes

Bimolecular rate constants for the reaction of ground-state Cl(2P3/2) atoms and for quenching of excited spin−orbit state Cl*(2P1/2) atoms in collisions with CH4, CD4, and CH2D2 have been measured at room temperature. Chlorine atoms were produced by the photolysis of CCl2F2 and HCl at 193 nm and monitored by the technique of laser-induced fluorescence at the vacuum ultraviolet region. The rate constants for the reaction of Cl atoms were found to be as follows: CH4, (10.0 ± 1.0) × 10-14; CH2D2, (7.0 ± 0.8) × 10-14; and CD4, (8.2 ± 1.0) × 10-15 cm3 molecule-1 s-1. The absolute second-order rate constants for the removal of Cl* atoms were as follows: CH4, (3.0 ± 0.3) × 10-11; CH2D2, (1.1 ± 0.1) × 10-10; and CO2, (1.2 ± 0.1) × 10-11 cm3 molecule-1 s-1. The removal of Cl* atoms was shown to proceed mainly by collisional quenching.