We report the high-resolution photoassociation (PA) spectroscopy of a ${}^{87}\mathrm{Rb}$ Bose-Einstein condensate (BEC) to excited molecular states near the dissociation limit of $5P_{1/2}+5S_{1/2}$ by optical Bragg scattering. Since the detection of optical Bragg scattering in the BEC has a high signal-noise ratio, we obtain the high-resolution PA spectrum of excited molecular states in the range of $\pm 1$ GHz near the dissociation limit of $5P_{1/2}+5S_{1/2}$. We compare the results with the conventional method of trap loss and show that the results agree with each other very well. Many interesting phenomena of excited molecular states are observed, such as light-induced frequency shift and anomalous strong bound molecular lines at the atomic transition from $|F=1\rangle$ to $|F^{\prime }=2\rangle$. The observed excited molecular states in the range of $\pm 1$ GHz near the dissociation limit of $5P_{1/2}+5S_{1/2}$ should help to further improve long-range bound-state models near the dissociation limit.

• Received 12 April 2020
• Revised 25 June 2020
• Accepted 16 October 2020

DOI:https://doi.org/10.1103/PhysRevA.102.053326