We probe the dynamics of dissociating CS_{2} molecules across the entire reaction pathway upon excitation. Photoelectron spectroscopy measurements using laboratory-generated femtosecond extreme ultraviolet pulses monitor the competing dissociation, internal conversion, and intersystem crossing dynamics. Dissociation occurs either in the initially excited singlet manifold or, via intersystem crossing, in the triplet manifold. Both product channels are monitored and show that, despite being more rapid, the singlet dissociation is the minor product and that triplet state products dominate the final yield. We explain this by a consideration of accurate potential energy curves for both the singlet and triplet states. We propose that rapid internal conversion stabilizes the singlet population dynamically, allowing for singlet-triplet relaxation via intersystem crossing and the efficient formation of spin-forbidden dissociation products on longer timescales. The study demonstrates the importance of measuring the full reaction pathway for defining accurate reaction mechanisms.
Femtosecond pump-probe photoelectron spectroscopy measurements using an extreme ultravioletprobe have been made on the photodissociation dynamics of UV (269 nm) excited CH3I. TheUV excitation leads to population of the 3Q0...
The products formed following the photodissociation of UV (200 nm) excited CS 2 are monitored in a time resolved photoelectron spectroscopy experiment using femtosecond XUV (21.5 eV) photons. By spectrally resolving the electrons we identify separate photoelectron bands related to the CS 2 + hν −→ S( 1 D) + CS and, CS 2 + hν −→ S( 3 P) + CS dissociation channels which show different appearance and rise times. The measurements show that there is no delay in the appearance of the S( 1 D) product contrary to the results of J. Chem. Phys. 147, 013932 (2017). Analysis of the photoelectron yield associated with the atomic products allows us to obtain a S( 3 P)/S( 1 D) branching ratio and the rate constants associated with dissociation and intersystem crossing rather than the effective lifetime observed through the measurement of excited state populations alone.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.