Cause of asymmetric and broadened molecular lineshape at 4.78 G

Determine the physical mechanism responsible for the observed asymmetric and significantly broadened lineshape of the v=0 Rb*Cs ultralong-range Rydberg molecular resonance (below the Rb 36S state) when both atoms are trapped in the same 1066 nm optical tweezer at a magnetic field of 4.78 G, and explain why this lineshape anomaly persists across all molecular resonances measured in that configuration.

Background

In the reported spectroscopy of individual Rb*Cs Rydberg molecules formed in a single 1066 nm tweezer, the authors observe molecular loss features corresponding to vibrational states below the atomic 36S threshold. Exact counting suggests pair loss dynamics consistent with radiative decay ejecting both atoms from the trap, and the v=0 state is identified near −31 MHz detuning.

However, the lineshape of the v=0 feature is found to be asymmetric and substantially broader than theoretical expectations. This unexpected broadening and asymmetry persist for all molecular resonances observed at 4.78 G in the same tweezer, indicating an unresolved mechanism affecting the spectroscopy in this configuration.