Observation of photoassociation spectroscopy of ultralong 37D + 6SCs Rydberg molecules.

We present an experimental observation of 37D + 6SCs Rydberg-ground molecules by employing a two-photon photoassociation method. Two distinct Rydberg-ground molecular signals, deep and shallow bound molecules, are observed at the red detuning of atomic line. In theory, the model of scattering interaction between the Rydberg electron and ground-state atom is used to simulate the experiments. Two potential energy curves with energy minimum, deep pure triplet Σ and shallow hyperfine-mixed singlet-triplet Σ potentials, refer to the attained Rydberg-ground molecular signals, respectively. Calculations of the binding energy of triplet Σ and mixed Σv = 0 states are compared with the measurements. The agreement between the calculated and measured values of the binding energy yields zero-energy scattering lengths a (0) = -19.2a and a (0) = -1.3a, respectively.