Investigations of the Reactions of 1CH2 (ã1A1 (v = 0,1)) with H2O, D2O and HCl

Abstract

AbstractThe reactions of 1CH2(ã1A1) in its vibrational ground state (1CH2(v = 0)) and with single excited bending mode (1CH2(v = 1)) with the reactants H2O (1), D2O (2) and HCl (3) were investigated with a LIF apparatus under quasistationary and first order conditions. 1CH2 was produced via ketene photolysis at 308 nm (1CH2(v = 0) and 1CH2(v = 1)) and at 336 nm (only 1CH2(v = 0)). The evaluation of the kinetic data of 1CH2(v = 0) gave different results for both wavelength. At λ = 336 nm obtained rate constants were in general higher compared to those at λ = 308 nm. The measurements at λ = 308 nm therefore seem to be influenced by secondary processes and they do not give the ‘real rate constant’.1CH2(v = 1) reacts faster with all three investigated reactants than 1CH2(v = 0) does. Vibrational deactivation with unusual high rate constants may explain these different reactivities of 1CH2(v = 0) and 1CH2(v = 1), but can only in part explain differences for the two 1CH2(v = 0) measurements.The following rate constants were measured at T = 295 K (in cm3·mol−1·s−1): k1(1CH2(v = 0)) = (1.45 ± 0,1)·1014, k1(1CH2(v = 1)) = (2.3 ± 0.2)·1014, k2(1CH2(v = 0)) ≈ 1.1·1014, k2(1CH2(v = 1)) = (1.75 ± 0.15)·1014, k3(1CH2(v = 0)) = (2.0 ± 0.2)·1014, and k3(1CH2(v = 1)) = (2.2±0.2)·1014.In the range from 255 K to 475 K the rate constants of the reactions of 1CH2(v = 0,1) with H2O and D2O show a significant dependence on temperature T which can be expressed by T−n with n = 0.6 to 0.8.The channel of the reaction of 1CH2 + H2O leading to CH3 + OH was found to contribute 50±15% to the total reaction, thus being the main channel at p ≤ 14 mbar. Formaldehyde could not be detected as a product of (1).