Torsion-Rotational Transitions in Methanol as a Probe of Fundamental Physical Constants—Electron and Proton Masses

We report on the using of torsion-rotational transitions in the CH 3 OH and 13 CH 3 OH molecules to evaluate possible variations of the electron-to-proton mass ratio μ = m e / m p from spectral observations of emission lines detected in the microwave range towards the dense molecular cloud Orion-KL. An estimate of the upper limit on the relative changes in μ is obtained by two independent ways with 13 CH 3 OH lines and with the combination of 13 CH 3 OH and CH 3 OH lines. The calculated upper limit Δμ/μ < 1.1 × 10 –8 (1σ) is in line with the most stringent constraints on the variability of fundamental physical constants established by other astrophysical methods.