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 CH3OH and (13)CH3OH molecules to evaluate possible variations of the physical constant mu=m_e/m_p - the electron-to-proton mass ratio - 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 mu is obtained by two independent ways - with (13)CH3OH lines and with the combination of (13)CH3OH and CH3OH lines. The calculated upper limit Delta mu/mu < 1.1*10⁻⁸ (1 sigma) is in line with the most stringent constraints on the variability of fundamental physical constants established by other astrophysical methods.