Photodissociation of singlet ketene by two-step IR+UV excitation

The dissociation of ketene on its singlet potential energy surface has been studied using a two-step photoexcitation, followed by state-selective detection of the CH2 radical via laser-induced fluorescence (LIF). For the first step near 2.8 micrometers , a commercial optical parametric oscillator was actively stabilized with an external reference etalon, allowing scan durations of up to 1 hour. By tuning the wavelength of the UV photolysis laser, photofragment excitation spectra of high energy selectivity were recorded. Comparison with phase space theory calculations shows that the projection K of the angular momentum onto the molecular axis is strongly mixed for K > 0 and that for K equals 0 the extent of mixing increases with J.