Quantum-classical dynamics of the capture of neon atoms by superfluid helium nanodroplets

Abstract

The capture of a Ne atom by a superfluid helium nanodroplet, Ne + (⁴He)_N → Ne@(⁴He)_N′ + (N − N′) ⁴He, was studied using a hybrid quantum (helium)–classical (Ne) approach and taking into account the angular momentum. The atom is captured by (⁴He)_N and follows elliptical rotating trajectories, and large energy and angular momentum transfer from the atom to the nanodroplet occur. Evaporation of helium atoms from (⁴He)_N allows removal of the excess energy and angular momentum of the doped nanodroplet. The behaviours observed for angular momentum different from zero are similar to the zero angular momentum case. The angular momentum of the Ne atom can induce vortex nucleation for high enough initial angular momentum values (∼176.3–220.3 ℏ). Vortices arise from collapse of the surface excitations (ripplons) and are long-lived under some initial conditions. Comparison with our own previous quantum dynamics study at zero angular momentum shows that quantum effects are not important under the initial conditions examined here. Besides, a comparison with the scarce information available on other systems has been performed, showing the rich variety of behaviours that can be observed in the solvation of impurities by superfluid helium. More efforts are welcome in order to obtain a deeper insight into the dynamics of the capture process, especially in the vortex formation context.