Sensitivity to a variation of me/mp from splittings between 12C2HD reference frequencies

Abstract

The sensitivity to a variation of μ of the 2v1 and v1+v3+v5 bands transitions of 12C2HD in the 193–199 THz spectral domain is calculated with an effective Hamiltonian for the Coriolis interaction between the [200(00)0e] and [101(01)1e] energy levels. The frequency splittings between near resonant transitions have sensitivity coefficients to a variation of μ of both signs in the range of 10–105. The degeneracy is due to a cancellation of effective rotational intervals with frequency shifts associated to the vibrational band origins, the anharmonicity and the rotation-vibration interactions. The measurements of a temporal drift of a frequency splitting against the Cs hyperfine frequency may constrain the time variation of μ better than the time variations of α, gCs. The systematic frequency shifts are evaluated for intracavity saturated absorption spectroscopy measurements and constrain the measurement of a variation of μ at ∼10−10. The comparison between measurements of frequency splittings with sensitivity coefficients of both signs may discriminate a variation of μ at −8×10−11.