High sensitivity to mass-ratio variation in deep molecular potentials

TL;DR

This paper identifies highly sensitive, narrow-linewidth vibrational transitions in deep molecular potentials of ${ m O}_2^+$, enabling more precise tests for variations in the proton-to-electron mass ratio.

Contribution

It discovers new high-sensitivity, electric-dipole forbidden transitions in ${ m O}_2^+$ that can improve measurements of fundamental constant variations.

Findings

Identified transitions with enhanced sensitivity due to vibrational degeneracies

Proposed experimental methods for measuring mass-ratio variation with higher precision

Transitions are narrow and suitable for high-precision spectroscopy

Abstract

Molecular vibrational transitions are prime candidates for model-independent searches for variation of the proton-to-electron mass ratio. Searches for present-day variation achieve highest sensitivity with deep molecular potentials. We identify several high-sensitivity transitions in the deeply bound ${\rm O}_2^+$ molecular ion. These transitions are electric-dipole forbidden and thus have narrow linewidths. The most sensitive transitions take advantage of an accidental degeneracy between vibrational states in different electronic potentials. We suggest experimentally feasible routes to a measurement with uncertainty exceeding current limits on present-day variation in $m_p/m_e$.