PRODUCTION OF CH(X (2)PI) FROM THE MULTIPHOTON DISSOCIATION OF CH2CO AT WAVELENGTHS OF 279.3 AND 308 NM

CH(X 2PI) has been observed by laser-induced fluorescence (LIF) spectr oscopy as the product of the two-photon dissociation of ketene (CH2CO) at 279.3 and 308 nm. The nascent distribution of rotational levels is Gaussian in profile, consistent with a 'rotational reflection' princi ple in the dissociation. Thermodynamic arguments imply a fragmentation pathway to CH + HCO following an initial one-photon absorption to the 1A'' excited state of ketene, a second photon absorption, and dissoci ation following rearrangement via a formylmethylene isomer. Analysis o f A doublets in the LIF spectra shows no orbital alignment of CH produ ced on photolysis at 279.3 nm, but some propensity for PI (A') symmetr y alignment (pi orbital of CH parallel to the plane of rotation) for p hotolysis at 308 nm.