Dynamics of solvation and desolvation of rubidium attached to He nanodroplets

TL;DR

This study investigates the ultrafast dynamics of rubidium atoms attached to helium nanodroplets, revealing state-dependent solvation and desolvation processes through femtosecond pump-probe mass spectrometry.

Contribution

It provides the first real-time measurements of Rb atom desolvation and ionization dynamics on helium nanodroplets, highlighting state-specific transition times.

Findings

Rb* desorbs from droplets at ~600 fs (6pSigma) and ~1200 fs (6pPi)

Rb+ ions tend to sink into droplets upon formation

Rb+He ions are produced via excitation of Rb*He exciplexes and photoassociative ionization

Abstract

The real-time dynamics of photoexcited and photoionized rubidium (Rb) atoms attached to helium (He) nanodroplets is studied by femtosecond pump-probe mass spectrometry. While excited Rb atoms in the perturbed 6p-state (Rb*) desorb off the He droplets, Rb^+ photoions tend to sink into the droplet interior when created near the droplet surface. The transition from Rb^+ solvation to full Rb* desorption is found to occur at a delay time t~600 fs for Rb* in the 6pSigma-state and t~1200 fs for the 6pPi-state. Rb^+He ions are found to be created by directly exciting bound Rb*He exciplex states as well as by populating bound Rb^+He-states in an photoassociative ionization process.