The role of Coulomb anti-blockade in the photoassociation of long-range Rydberg molecules

TL;DR

This paper investigates Coulomb anti-blockade, a mechanism where ions from decayed Rydberg molecules enhance the excitation of other atoms into Rydberg states, affecting detection methods in ultracold cesium gases.

Contribution

It introduces and characterizes Coulomb anti-blockade as a new ion-mediated excitation mechanism in the photoassociation of long-range Rydberg molecules.

Findings

Identification of ion-mediated excitation signatures in photoassociation spectra

Theoretical modeling of molecular level structures confirms the mechanism

Experimental data supports the role of Coulomb anti-blockade in detection

Abstract

We present a new 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 "Coulomb anti-blockade". Pulsed-field ionisation typically doesn't 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 nP_3/2 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.