Sensitivity of the isotopologues of hydronium to variation of the electron-to-proton mass ratio

TL;DR

This paper investigates how the microwave and submillimeter transitions of hydronium isotopologues are highly sensitive to changes in the electron-to-proton mass ratio, especially for low-frequency mixed inversion-rotational transitions, with potential implications for astrophysical studies.

Contribution

It provides new insights into the sensitivity of hydronium isotopologues' transitions to variations in the electron-to-proton mass ratio, highlighting transitions with sensitivities much higher than previously used molecules.

Findings

Lowest frequency transition (6.6 GHz) in H2DO+ has sensitivity close to 200.

Sensitivity is about two orders of magnitude larger than ammonia inversion transition.

Enhanced sensitivity for low frequency mixed inversion-rotational transitions.

Abstract

We study the sensitivity of the microwave and submillimeter transitions of the isotopologues of hydronium to the variation of the electron-to-proton mass ratio mu. These sensitivities are enhanced for the low frequency mixed inversion-rotational transitions. The lowest frequency transition (6.6 GHz) takes place for isotopologue H2DO+ and respective sensitivity to mu-variation is close to 200. This is about two orders of magnitude larger than the sensitivity of the inversion transition in ammonia, which is currently used for the search of mu-variation in astrophysics.