Laser induced fluorescence of CH 2 (ã 1A 1) produced in the photodissociation of ketene at 337 nm. The CH 2 (ã 1A 1-X̃ 3B 1)energy separation

Abstract

The photodissociation of ketene, CH 2CO(X̃ 1A 1) → CH 2 (ã 1A 1) + CO(X 1Σ +) has been observed at 337 nm, using a pulsed nitrogen laser. The CH 2 (ã 1A 1) radical has been detected by laser induced fluorescence with a tunable dye laser. A laser excitation spectrum has been obtained from CH 2(ã 1A 1) over the wavelength interval from 588.9 to 595.6 nm in the Σ ← Π vibronic subband of the CH 2 (ã 1A 1); υ″ = 0, 0, 0−b̃ 1B 1; υ′ = 0, 14, 0) transition. For the CH 2(ã 1A 1 ; υ′= 0, 0, 0−X̃ 3B 1; υ′' = 0, 0, 0) energy separation an upper limit of (6.3 ± 0.8) kcal/mole has been found. The radiative lifetime τ and the rate constant k for the removal of the 0 00 rotational level of the Σ(0, 14, 0) vibronic state have been measured directly. The values are τ = (4.2 ± 0.2) μs and k = (7.4 ± 0.3) × 10 −10 cm 3 molecule −1 s −1, respectively.