State Correlations in the Unimolecular Dissociation of Ketene

Doppler-broadened absorption spectra of selected rotational levels of singlet CH 2 fragments from the 308-nm photolysis of ketene have been observed by frequency-modulated transient absorption spectroscopy in a slit jet expansion. Nascent Doppler profiles of CH 2 transitions have been analyzed to yield the internal energy distributions of coincident CO fragments at a total energy 2333 cm -1 above the singlet dissociation threshold. The vibrational branching ratio of CO (υ = 1):(υ = 0) is determined in coincidence with selected rotational levels of CH 2 . The coincident rotational distributions of CO (υ = 0) are also estimated and found to differ from simple statistical predictions, revealing a relative deficiency of those pairs in which both fragments have a low internal energy.