Measurement of the variation of electron-to-proton mass ratio using ultracold molecules produced from laser-cooled atoms

TL;DR

This study uses ultracold KRb molecules to measure the electron-to-proton mass ratio with high precision, setting new limits on its temporal variation and demonstrating the potential for further improvements.

Contribution

It presents a novel high-precision measurement of the electron-to-proton mass ratio variation using ultracold molecules, surpassing previous laboratory limits.

Findings

Limit on variation of μ: (0.30 ± 1.0) × 10^{-14} year^{-1}

Measurement improved by a factor of five over previous best

Results limited only by statistical errors

Abstract

Experimental techniques to manipulate cold molecules have seen great development in recent years. The precision measurements of cold molecules are expected to give insights into fundamental physics. We use a rovibrationally pure sample of ultracold KRb molecules to improve the measurement on the stability of electron-to-proton mass ratio ($\mu = \frac{m_{\rm e}}{M_{\rm p}}$). The measurement is based upon a large sensitivity coefficient of the molecular spectroscopy, which utilizes a transition between nearly a degenerate pair of vibrational levels each associated with a different electronic potential. Observed limit on temporal variation of $\mu$ is $\frac{1}{\mu}\frac{d\mu}{dt} = (0.30\pm1.0) \times 10^{-14}$ year$^{-1}$, which is better by a factor of five compared with the most stringent laboratory molecular limits to date. Further improvements should be straightforward, because our measurement was only limited by statistical errors.