Generating Molecular Rovibrational Coherence by Two-Photon Femtosecond Photoassociation of Thermally Hot Atoms

TL;DR

This paper demonstrates the experimental generation of molecular rovibrational coherence in hot atoms via two-photon femtosecond photoassociation, supported by theoretical modeling, paving the way for coherent control of binary reactions.

Contribution

It introduces a novel experimental method to produce and analyze rovibrational coherence in hot atomic gases, supported by ab initio theoretical insights.

Findings

Rovibrational coherence observed in hot magnesium atoms.

Quantum beats in UV fluorescence indicate coherence.

Theoretical model explains coherence generation via Franck-Condon filtering.

Abstract

The formation of diatomic molecules with rotational and vibrational coherence is demonstrated experimentally in free-to-bound two-photon femtosecond photoassociation of hot atoms. In a thermal gas at a temperature of 1000 K, pairs of magnesium atoms, colliding in their electronic ground state, are excited into coherent superpositions of bound rovibrational levels in an electronically excited state. The rovibrational coherence is probed by a time-delayed third photon, resulting in quantum beats in the UV fluorescence. A comprehensive theoretical model based on ab initio calculations rationalizes the generation of coherence by Franck-Condon filtering of collision energies and partial waves, quantifying it in terms of an increase in quantum purity of the thermal ensemble. Our results open the way to coherent control of a binary reaction.