Impact of Nuclear Motion on Light-Induced Bimolecular Interaction Dynamics

Abstract

In chemical reactions, the nuclear motion of the molecules plays a crucial role in determining the reaction rates and outcomes. Employing the cold target recoil ion momentum spectroscopy and femtosecond pump-probe techniques, we perform a molecular-level study into the influence of nuclear vibrations on light-induced bimolecular reactions within H_{2}-D_{2} dimers. The study focuses on the formation dynamics of D_{2}H^{+} and H_{2}D^{+} cations, shedding light on the interplay between translational and vibrational motions of the nuclei steering the bimolecular reactions. Our observations reveal a notable yield ratio of 1:1.6 between H_{2}D^{+} and D_{2}H^{+} channels, accompanied with a faster formation of D_{2}H^{+} compared to H_{2}D^{+}. Molecular dynamics simulations unveil that the faster vibrational motion of H_{2}^{+} than that of D_{2}^{+} upon single ionization within the dimer accounts for these differences. Our findings provide new insight into the time-resolved kinetic isotope effect on the bimolecular reactions, highlighting the critical relationship between nuclear vibrational motions and reaction dynamics.