Nanosecond versus picosecond near UV multiphoton dissociation of ketene

The multiphoton dissociation of ketene at 308 and 290.5 nm has been studied using different laser pulse widths of 15 ns, 4 ns and 10 ps by observing the photofragment fluorescence in a static cell. Efficient emission from CH(A 2Δ) and (B 2Σ−) was detected in both nanosecond and picosecond experiments. C2 Swan bands were observed only with nanosecond pulses. These results are discussed invoking the competition between multiphoton absorption by the parent molecule and dissociation into possible intermediate photofragment precursors.