Intramolecular large amplitude motions as a probe of a possible proton-to-electron mass ratio variation

During the last decades there has been an active search for physics beyond the Standard Model. Discovery of variations of the Standard Model constants in space or in time would be an unambiguous indication of new physics. Search for drifting constants on large spatial and temporal scales is carried out via observing spectra of the interstellar gas both in our Galaxy and at large redshifts. Recently it was shown that microwave spectra of molecules with large amplitude motions (tunneling transitions) are highly sensitive to a proton-to-electron mass ratio variation. The theoretical aspects of estimation of sensitivity of molecular transitions to a possible variation of the proton-to-electron mass ratio are discussed and the needs for new experimental spectroscopic data in the microwave range are considered.