According theory and experiment in CaH: Laser-induced fluorescence study of new B/B′-X bands in the UV region

Despite the astrophysical importance of calcium monohydride (CaH), a long-standing discrepancy exists between the experimental and theoretical analysis of its first two excited ²Σ⁺ states. In a bid to resolve this discrepancy, we observed the rotationally-resolved laser-induced fluorescence spectrum of CaH in the 23,300-27,800 cm^-1 region. We assigned all newly observed vibrational levels, and five levels previously assigned to the D state, to the B/B′ state. The level properties alternate strongly with vibrational excitation and this new assignment brings the experimental vibronic structure into remarkably good agreement with the predictions of Carlsund-Levin et al. (2002).