Quantum-classical lifetimes of Rydberg molecules

TL;DR

This paper investigates the reduced lifetimes of Rydberg molecules compared to Rydberg atoms, using a quantum-classical model to explain the detuning effects caused by the ground state atom.

Contribution

It introduces a quantum-classical approach to explain the reduced lifetimes of Rydberg molecules, highlighting the role of detuning caused by the ground state atom.

Findings

Detuning of the Rydberg wave function explains lifetime reduction.

Timescale of detuning matches observed lifetime decrease.

Quantum-classical model aligns with experimental data.

Abstract

A remarkable property of Rydberg atoms is the possibility to create molecules formed by one highly excited atom and another atom in the ground state. The first realisation of such a Rydberg molecule has opened an active field of physical investigations, and showed that its basic properties can be described within a simple model regarding the ground state atom as a small perturber that is bound by a low-energy scattering process with the Rydberg electron [C. H. Greene et al, Phys. Rev. Lett., 85: 2458 (2000)]. Besides the good agreement between theory and the experiment concerning the vibrational states of the molecule, the experimental observations yield the astonishing feature that the lifetime of the molecule is clearly reduced as compared to the bare Rydberg atom [B. Butscher et al, J. Phys. B: At. Mol. Opt. Phys. 44, 184004 (2011)]. With focus on this yet unexplained observation, we investigate in this paper the vibrational ground state of the molecule in a quantum-classical framework. We show that the Rydberg wave function is continuously detuned by the presence of the moving ground state atom and that the timescale on which the detuning significantly exceeds the natural linewidth is in good agreement with the observed reduced lifetimes of the Rydberg molecule.