Detailed study of dissipative quantum dynamics of K-2 attached to helium nanodroplets

TL;DR

This paper provides a comprehensive quantum dynamical analysis of K-2 dimers on helium nanodroplets, revealing how droplet-induced effects like decoherence, potential shifts, and desorption influence vibrational dynamics, aligning theory with experimental observations.

Contribution

It offers a detailed, step-by-step quantum model including droplet effects and desorption, advancing understanding of vibrational dynamics of molecules on helium droplets.

Findings

Desorption occurs within 2-10 ps after excitation.

Droplet effects cause electronic decoherence and potential shifts.

Vibrational motion in the ground state is frictionless.

Abstract

We thoroughly investigate vibrational quantum dynamics of dimers attached to He droplets motivated by recent measurements with K-2 [1]. For those femtosecond pump-probe experiments, crucial observed features are not reproduced by gas phase calculations but agreement is found using a description based on dissipative quantum dynamics, as briefly shown in [2]. Here we present a detailed study of the influence of possible effects induced by the droplet. The helium droplet causes electronic decoherence, shifts of potential surfaces, and relaxation of wave packets in attached dimers. Moreover, a realistic description of (stochastic) desorption of dimers off the droplet needs to be taken into account. Step by step we include and study the importance of these effects in our full quantum calculation. This allows us to reproduce and explain all major experimental findings. We find that desorption is fast and occurs already within 2-10 ps after electronic excitation. A further finding is that slow vibrational motion in the ground state can be considered frictionless.