Theoretical study on photoexcitation dynamics of the K atom attached to helium clusters and the solvation structures of K*Hen exciplexes

Abstract

The dynamics of the K atom attached to the 300-atom helium cluster upon photoexcitation has been studied theoretically based on the quantum molecular dynamics method. With the use of a hybrid method between time-dependent quantum dynamics and semiclassical path integral centroid molecular dynamics, the calculation includes the electronic state mixing for the K(2P) states as well as the quantum motions of helium atoms. It was found from the calculated trajectories that the K atom mostly desorbs by itself from the surface of the helium cluster without depending on the types of initial electronic excited states. It was also found that the K*He exciplex can be formed only as a minor product, following the initial excitation to the Π-type electronic state alone. Helium solvation structures of the K*Hen exciplexes were also investigated by path integral molecular dynamics simulations. The result implies that stable exciplexes can be formed up to n = 6 on the lowest excited state until the first solvation shell around the 4p orbital of K* is completed. Meanwhile, it was found that only two helium atoms can be bound to the K(2P) atom on the second lowest excited state.