Role of Coulomb antiblockade in the photoassociation of long-range Rydberg molecules

We present a mechanism contributing to the detection of photoassociated long-range Rydberg molecules via pulsed-field ionization: ionic products, created by the decay of a long-range Rydberg molecule, modify the excitation spectrum of surrounding ground-state atoms and facilitate the excitation of further atoms into Rydberg states by the photoassociation light. Such an ion-mediated excitation mechanism has been previously called a Coulomb antiblockade. Pulsed-field ionization typically does not discriminate between the ionization of a long-range Rydberg molecule and an isolated Rydberg atom, and thus the number of atomic ions detected by this mechanism is not proportional to the number of long-range Rydberg molecules present in the probe volume. By combining high-resolution UV and rf spectroscopy of a dense, ultracold gas of cesium atoms, theoretical modeling of the molecular-level structures of long-range Rydberg molecules bound below n 2P3/2 Rydberg states of cesium, and a rate model of the photoassociation and decay processes, we unambiguously identify the signatures of this detection mechanism in the photoassociation of long-range Rydberg molecules bound below atomic asymptotes with negative Stark shifts.

Automated summary

We propose a mechanism for detecting photoassociated long-range Rydberg molecules via pulsed-field ionization, where ionic products from the decay of a long-range Rydberg molecule modify the excitation spectrum of surrounding ground-state atoms, facilitating the excitation of more atoms into Rydberg states. This ion-mediated excitation mechanism, known as Coulomb antiblockade, does not discriminate between long-range Rydberg molecules and isolated Rydberg atoms during ionization, resulting in the detected number of atomic ions not being proportional to the number of long-range Rydberg molecules present.