Stability of the proton-to-electron mass ratio

TL;DR

This paper sets a limit on how much the proton-to-electron mass ratio can vary over time by comparing molecular and atomic transition frequencies with high precision, providing a direct and model-free measurement.

Contribution

It introduces a novel, direct, and model-free method to constrain the temporal variation of the proton-to-electron mass ratio using molecular and atomic frequency comparisons.

Findings

No significant variation detected within measurement limits.

Provides the most stringent limit to date on the variation of the proton-to-electron mass ratio.

Demonstrates the effectiveness of using rovibrational and hyperfine transitions for fundamental constant tests.

Abstract

We report a limit on the fractional temporal variation of the proton-to-electron mass ratio as, obtained by comparing the frequency of a rovibrational transition in SF6 with the fundamental hyperfine transition in Cs. The SF6 transition was accessed using a CO2 laser to interrogate spatial 2-photon Ramsey fringes. The atomic transition was accessed using a primary standard controlled with a Cs fountain. This result is direct and model-free.