The influence of the optical pulse shape on excited state dynamics in provitamin D-3

Broadband visible transient absorption spectroscopy was used to characterize the excited state population of 7-dehydrocholesterol (provitamin D-3, DHC) following excitation by UV pulses with systematically varied linear chirp. These experiments demonstrate that the phase of the excitation pulse can modify the observed excited state decay. The results suggest that coherent mechanisms involving multiple interfering pathways may be exploited to control branching between excited state pathways and manipulate product formation.