Light-induced frequency shifts for the lowest vibrational levels of ultracold Cs2 in the molecular pure long-range $$0_g^-$$ state

The light-induced frequency shift (LIFS) of ultracold molecular ro-vibrational levels originates from the strong coupling of the atomic-scattering state and the bound-molecular state. In this paper, we present our experimental determination of the LIFSs of the lowest vibrational levels (ν = 0, 1) in the purely long-range $$0_g^-$$ state of ultracold cesium molecules. A high-resolution double photoassociation spectroscopy is developed, which serves as frequency ruler to measure the frequency shifts of the lowest molecular levels for Cs2. The experimental results are qualitatively consistent with the theoretical expectations.