State correlations in the unimolecular dissociation of ketene

Doppler-broadened absorption spectra of selected rotational levels of singlet CH₂ 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 CH₂ 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 (v = 1):(v = 0) is determined in coincidence with selected rotational levels of CH₂. The coincident rotational distributions of CO (v = 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.