Extending electron orbital precession to the molecular case: Can orbital alignment be used to observe wavepacket dynamics?

TL;DR

This paper models ultrafast molecular photoionization in rubidium dimers, predicting observable spin-orbit precession and vibrational motion through pump-probe experiments, advancing understanding of wavepacket dynamics.

Contribution

It introduces a combined atomic and molecular dynamics model to predict pump-probe experiment outcomes in rubidium molecules, highlighting feasible experimental observations.

Findings

Spin-orbit precession observable with suitable pump pulses.

High-frequency beat signals decay within tens of picoseconds.

Vibrational motion detectable via ionization cross section oscillations.

Abstract

The complexity of ultrafast molecular photoionization presents an obstacle to the modelling of pump-probe experiments. Here, a simple optimized model of atomic rubidium is combined with a molecular dynamics model to predict quantitatively the results of a pump-probe experiment in which long range rubidium dimers are first excited, then ionized after a variable delay. The method is illustrated by the outline of two proposed feasible experiments and the calculation of their outcomes. Both of these proposals use Feshbach 87Rb2 molecules. We show that long-range molecular pump-probe experiments should observe spin-orbit precession given a suitable pump-pulse, and that the associated high-frequency beat signal in the ionization probability decays after a few tens of picoseconds. If the molecule was to be excited to only a single fine structure state state, then a low-frequency oscillation in the internuclear separation would be detectable through the timedependent ionization cross section, giving a mechanism that would enable observation of coherent vibrational motion in this molecule.