Photodissociation Dynamics of Homonuclear Diatomic Molecules in Helium Nanodroplets. The Case of Cl₂@(⁴He)N.

Abstract

To investigate the photodissociation dynamics of diatomic homonuclear molecules in helium nanodroplets, a hybrid quantum mechanical theoretical method that combines time dependent density functional theory (helium) and quantum dynamics (molecule) has been developed. This method has been applied to investigate the Cl2 photodissociation arising from the B ← X electronic transition, considering Cl2(v = 0,X)@((4)He)N nanodroplets with N = 50, 100, 200, 300, and 500 (initial configuration for the dynamics). A time scale of a few picoseconds has been determined, and the time required for the dissociating atoms to reach the nanodroplet surface increases with N. Moreover, at the high velocities involved (orders of magnitude above the Landau's critical velocity), an efficient energy exchange between the chlorine atoms and the helium takes place, releasing up to 91% of the energy of the excited diatomics for the bigger nanodroplet considered; and the energy exchange mechanism is the same for all the nanodroplets. Finally, simple (linear) relations for the average Cl final velocity and the (small) number of evaporated He atoms with respect to the radius of the droplets have been reported, together with the existence of confinement resonances. We hope that these results will encourage the experimentalists to investigate this kind of systems.