Exit-channel recoil resonances by imaging the photodissociation of single quantum-state-selected OCS molecules

Abstract

In a recent letter [Phys. Rev. Lett. 118, 253001 (2017)] we have described how studies of the recoil velocity distribution in the photodissociation of OCS in the energy interval 42 600--42 900 ${\mathrm{cm}}^{\ensuremath{-}1}$ revealed an unexpected behavior: the recoil velocity distribution of only the lowest-kinetic-energy photofragments exhibited rapid, resonantlike variations with energy and caused complete inversion of the recoil direction. Periodic orbit analysis and quantum nonadiabatic calculations unveiled the existence of a resonance state localized at large bending angles towards the exit of the dissociation channel. In this article, we present an extensive theoretical study and we show how the fingerprints of these resonances are identified by the analysis of the nonadiabatic transitions and the stereodynamics of photofragments trajectories. Additionally, the experimental study is extended to a second photolysis energy region, 43 300--43 650 ${\mathrm{cm}}^{\ensuremath{-}1}$, where a similar rapid variation of the recoil direction is detected. The energy separation between this second resonance region and the one previously reported is $\ensuremath{\sim}800\phantom{\rule{0.28em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$, which is twice the calculated period of the localized resonant state, offering a second point of convergence between the experiment and the theory.