Acetaldehyde as a molecule for testing variations of electron-to-proton mass ratio

TL;DR

This study calculates how sensitive acetaldehyde molecular transitions are to changes in the electron-to-proton mass ratio, providing a method to test fundamental constant variations in space.

Contribution

It offers the first quantum-mechanical sensitivity coefficients for acetaldehyde transitions to mu variations, enabling new astrophysical tests of fundamental physics.

Findings

Sensitivity coefficients range from 0.62 to 3.61.

Limit on mu variation: Delta mu/mu = (0.1 +/- 0.4)*10^(-7).

Constraints on violations of local position invariance at 4*10^(-8).

Abstract

We present the quantum-mechanical calculations of the dimensionless sensitivity coefficients Q to small changes in the fundamental physical constant mu = m_e/m_p - the electron-to-proton mass ratio - for a number of low-frequency (1-50 GHz) transitions of the acetaldehyde (CH3CHO) molecule. The calculations show that Q varies in the range from 0.62 to 3.61. An example of the practical use of the CH3CHO and CH3OH lines tracing the same regions in three molecular clouds, located at large galactocentric distances (D_GC ~ 8 kpc) is considered. This results in a limit on the mu variations of Delta mu/mu = (0.1 +/- 0.4)*10^(-7) which is in line with previously obtained most stringent upper limits on changes in mu based on other molecules and methods. The limit obtained restricts hypothetical violations of the Einstein principle of the local position invariance at the level of 4*10^(-8) in the Galactic disk at large galactocentric distances.