Vibrational relaxation and dephasing of Rb2 attached to helium nanodroplets

TL;DR

This study investigates the vibrational relaxation and dephasing of Rb2 molecules on helium nanodroplets, combining experimental femtosecond spectroscopy with theoretical simulations to reveal relaxation rates and their dependence on vibrational levels.

Contribution

It provides a detailed analysis of vibrational relaxation mechanisms of Rb2 on helium nanodroplets using combined experimental and theoretical approaches, highlighting the relaxation rate's dependence on vibrational energy.

Findings

Vibrational relaxation is the main source of dephasing.

Relaxation rate constant is ~0.5 ns^-1 for v<15.

Relaxation rate increases sharply at higher vibrational levels.

Abstract

The vibrational wave-packet dynamics of diatomic rubidium molecules (Rb2) in triplet states formed on the surface of superfluid helium nanodroplets is investigated both experimentally and theoretically. Detailed comparison of experimental femtosecond pump-probe spectra with dissipative quantum dynamics simulations reveals that vibrational relaxation is the main source of dephasing. The rate constant for vibrational relaxation in the first excited triplet state is found to be constant ~0.5ns^-1 for the lowest vibrational levels v< 15 and to increase sharply when exciting to higher energies.