Optical-optical double-resonance spectroscopy of SrOH: The C˜2Π(000)-A˜2Π(000) transition

Optical-optical double-resonance spectroscopy has been used to record a high-resolution spectrum of the C˜2Π(000)-A˜2Π(000) transition of SrOH. Rotational and fine structure parameters have been determined for the C˜2Π state through a combined least-squares fit with the A˜2Π-X˜2Σ+ optical transition data and the millimeter-wave pure rotational data of the X˜2Σ+ state. The spin-orbit constant of the C˜2Π state was found to be 24.6607 cm−1, which is significantly smaller than in the Ã2Π state. This change can be rationalized by the different atomic orbital character of the Ã2Π and C˜2Π states. The values of the Λ-doubling constants in the C˜2Π state have been examined in terms of the pure procession model. The agreement between the calculated and observed Λ-doubling constants suggests that the C˜2Π state may form a unique perturber pair with the nearby D˜2Σ+ state.