Phase-modulated electronic wave-packet interferometry reveals high resolution vibronic spectra of free Rb atoms and Rb*He molecules

TL;DR

This study employs phase-modulated wave-packet interferometry with mass-resolved detection to achieve high-resolution vibronic spectra of free Rb atoms and Rb*He molecules, demonstrating enhanced sensitivity and resolving complex vibrational structures.

Contribution

It introduces a novel application of phase-modulated interferometry combined with mass-resolved detection to study cold gas phase molecules with unprecedented spectral resolution.

Findings

Enhanced spectral sensitivity compared to conventional methods

First fully resolved vibrational spectrum of Rb*He exciplex transitions

Demonstration of applying multidimensional spectroscopy to dilute cold gases

Abstract

Phase-modulated wave-packet interferometry is combined with mass-resolved photoion detection to investigate rubidium atoms attached to helium nanodroplets in a molecular beam experiment. The spectra of atomic Rb electronic states show a vastly enhanced sensitivity and spectral resolution when compared to conventional pump-probe wave-packet interferometry. Furthermore, the formation of Rb*He exciplex molecules is probed and for the first time a fully resolved vibrational spectrum for transitions between the lowest excited $5\Pi_{3/2}$ and the high-lying electronic states $2^2\Pi$, $4^2\Delta$, $6^2\Sigma$ is obtained and compared to theory. The feasibility of applying coherent multidimensional spectroscopy to dilute cold gas phase samples is demonstrated in these experiments.