Excited state magnetic hyperfine interactions in gas phase strontium and calcium monohydrides

Numerous rotational lines in the B²Σ⁺(v′ = 0)-X²Σ⁺(v″ = 0) band system of CaH and the A²Π _{1 2}(v′ = 0)-X²Σ(v″ = 0) subband system of SrH have been recorded at sub-Doppler resolution using the technique of intermodulated fluorescence. The recorded spectra exhibit a small splitting associated with magnetic hyperfine interactions in both the ground and the excited electronic states. An analysis of the excited state contributions was performed and the results were interpreted in terms of the possible nature of the electronic wavefunction. The results suggest that the effective Hamiltonian needs to be modified in order to give qualitative agreement for the Λ-doubling type magnetic hyperfine parameter. The determined hyperfine parameters for the B²Σ⁺ state are consistent with the current theoretical interpretation of the nature of this state.