The accurate determination of magnetic hyperfine and Zeeman parameters for 2∏ diatomic molecules from experimental data

The parameters γ and AD (for the spin-rotation coupling and the centrifugal correction to the spin-orbit coupling) in the effective Hamiltonian of a diatomic molecule in a 2Λ state, Λ ≠ 0, make indistinguishable contributions to the energy, and one or other of these terms can be removed by a unitary transformation. The present work considers the effects of this and other transformations on the terms of the magnetic hyperfine and Zeeman Hamiltonians. It is found that the hyperfine parameter b is particularly affected by the transformations, and that care must be taken in correcting b before interpreting its value in terms of the electronic structure. An application to 15NO gives consistent values of the corrected b between ÃD and γ̃ fits. The transformation of the Zeeman Hamiltonian produces higher order Zeeman terms that so far have not been included in fits of data in magnetic fields. Neglect of these contributions is equivalent to a constraint on the fit. A re-fit of LMR data for the FO radical shows that this approach is viable, and leads to the determination of separate values for AD and γ. These values and those obtained for b and gl correspond to the unitary transformation that optimizes the chosen form of the Zeeman Hamiltonian.