Bichromatic Photoassociation Spectroscopy for the Determination of Rotational Constants of Cs₂ <inline-formula> <mml:math display="block" id="mm1"> <mml:semantics> <mml:msubsup> <mml:mn mathvariant="bold">0</mml:mn> <mml:mi mathvariant="bold">u</mml:mi> <mml:mo mathvariant="bold">+</mml:mo> </mml:msubsup> </mml:semantics> </mml:math> </inline-formula> Long-Range State below the 6S_1/2 + 6P_1/2 Asymptote

Abstract

This article demonstrates new observation of the high-resolution ro-vibrational bichromatic photoassociation spectra (BPAS) of Cs2 in the 0u+ long-range state below the asymptotes 6S1/2 + 6P1/2. 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 Cs20u+ 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.

Keywords

• ultracold molecule
• diatomic molecules
• molecular spectra
• bichromatic photoassociation spectroscopy
• long-range state
• non-rigid-rotor model