Sensitivity of Tunneling-Rotational Transitions in Ethylene Glycol to Variation of Electron-to-Proton Mass Ratio

Ethylene glycol in its ground conformation has tunneling transition with the frequency about 7 GHz. This leads to a rather complicated tunneling-rotational spectrum. Because tunneling and rotational energies have different dependence on the electron-to-proton mass ratio $\mu$, this spectrum is highly sensitive to the possible $\mu$ variation. We used simple 14 parameter effective Hamiltonian to calculate dimensionless sensitivity coefficients $Q_\mu$ of the tunneling-rotational transitions and found that they lie in the range from $-17$ to $+18$. Ethylene glycol has been detected in the interstellar medium. All this makes it one of the most sensitive probes of $\mu$ variation at the large space and time scales.