Bichromatic Photoassociation Spectroscopy for the Determination of Rotational Constants of Cs(2) [Formula: see text] Long-Range State below the 6S(1/2) + 6P(1/2) Asymptote

This article demonstrates new observation of the high-resolution ro-vibrational bichromatic photoassociation spectra (BPAS) of Cs(2) in the [Formula: see text] long-range state below the asymptotes 6S(1/2) + 6P(1/2). By combining with a modulation spectroscopic technique, precise references of the frequency differences have been engineered through the BPAS, with which the rotational constants of low-lying vibrational levels of the Cs(2) [Formula: see text] long-range state have been accurately determined by fitting the frequency differences to the non-rigid-rotor model. The rotational constants for the newly observed seven ro-vibrational levels are summarized and disagreement for the level ῦ = 498 is clarified. The rotational constants of different vibrational levels demonstrate strong perturbations of the related energy structures. A simple analysis is performed and shows good agreement with experimental results.