# Laser-induced rotation of iodine molecules in He-nanodroplets: revivals and breaking-free

## TL;DR

This study investigates how laser pulses induce and control the rotation of iodine molecules in helium nanodroplets, revealing conditions for coherent revivals and their breakdown, which advances understanding of solute-solvent quantum dynamics.

## Contribution

It combines experimental laser alignment techniques with angulon theory to elucidate the rotational behavior of molecules in superfluid helium, highlighting the transition from collective to isolated-like rotation.

## Key findings

- Coherent rotational revivals occur at low laser fluence.
- High fluence causes revivals to disappear and rapid rotation to dominate.
- Transient decoupling of molecule and helium shell explains observed dynamics.

## Abstract

Rotation of molecules embedded in He nanodroplets is explored by a combination of fs laser-induced alignment experiments and angulon quasiparticle theory. We demonstrate that at low fluence of the fs alignment pulse, the molecule and its solvation shell can be set into coherent collective rotation lasting long enough to form revivals. With increasing fluence, however, the revivals disappear -- instead, rotational dynamics as rapid as for an isolated molecule is observed during the first few picoseconds. Classical calculations trace this phenomenon to transient decoupling of the molecule from its He shell. Our results open novel opportunities for studying non-equilibrium solute-solvent dynamics and quantum thermalization.