Zeeman molecular probe for tests of fundamental physical constants

ABSTRACT The impact of the Zeeman effect on the Λ-doublet spectra of diatomic radicals is analysed from the point of view of a possible cosmological variation of the proton-to-electron mass ratio, μ. The actual model calculations performed for the 2Π3/2 and 2Π1/2 states of 16OH reveal that the Λ-doublet energy levels of diatomic radicals can be tuned to degeneracy by means of the Zeeman effect using realistic magnetic fields. Tuning this degeneracy allows for a dramatic enhancement of the relative mass sensitivity coefficients of the corresponding transitions and for a substantial reduction of their Doppler broadening. Moreover, unlike their field-free counterparts associated with the degeneracies arising due to the A ∼ 4B situations (A and B being the spin–orbit and rotation constant, respectively), the electric dipole allowed e ↔f Zeeman-tuned transitions exhibit favourable intensities, thus evidencing their promising potential.