Radiative lifetime and quenching of the A 2A1 state of the CH3O radical

The laser-induced fluorescence technique has been employed to study the first excited electronic state à 2A1 of CH3O. Vibrational levels v′3 =0–7 of the à state were excited and fluorescence decay rates were measured. Compared to a value 2.2±0.2 μs at v3=0, a significant decrease of decay rate was found at 277.6 nm (0.89 μs, v′3=7). Excitation to higher levels further reduced the lifetime. The predissociation threshold was estimated to be slightly above 276 nm (36 220 cm−1). The electronic quenching rates of the à state (v′=0–2) by CH3OH, O2, NO2, and N2 have also been determined and are compared with those of OH in the à state.