Further spectroscopic investigations of the high energy electronic states of SrOH: The B∼′2Σ+(000)-A∼2Π(000) and the D∼2Σ+(000)-A∼2Π(000) transitions

The B∼′2Σ+ and D∼2Σ+ states of SrOH were investigated using optical-optical double-resonance (OODR) spectroscopy. Rotational and fine structure parameters have been determined for these two states through a combined least-squares fit of the current OODR data along with the OODR data of the C∼2Π-A∼2Π transition, the optical data of the A∼2Π-X∼2Σ+ transition and the millimeter-wave pure rotational measurements of the X∼2Σ+ state. The spin-rotation constant, γ, of the B∼′2Σ+ state was found to be 0.002653 cm−1, which is two orders of magnitude smaller than that of the B∼2Σ+ state (−0.1447 cm−1). This small γ value suggests that this state arises from a Sr+ atomic orbital of mainly 6sσ character. This atomic orbital assignment is also supported by the large rotational constant observed in the B∼′2Σ+ state and the similarity of the molecular constants to those of the D∼2Σ+ state of CaOH. The rotational energy levels of the D∼2Σ+state of SrOH were found to be largely perturbed, which prohibited the accurate determination of the spin-rotation constant in this state. This perturbation is most likely due to an interaction with a 2Σ vibronic component of the nearby C∼2Π state.