Autoionzation of long-range Rydberg molecules: measurement of the product state distribution

Long-range Rydberg molecules (LRMs) are exotic bound states of an atom in a Rydberg state to one or more ground-state atoms within the Rydberg electron's orbit. Besides fundamental interest in this exotic binding mechanism based on electron-neutral-atom scattering [1], creation of a dense gas of LRMs offers a potential route towards the formation of ultracold ion-pair plasmas, i.e., neutral plasmas with equal-mass charges of opposite sign [2]. We thus recently started a detailed investigation in the process of photoassociation of LRMs [3] and their stability. An important decay mechanism of LRMs is Hornbeck-Molnar ionization where coupling of the initial LRM state to the short-range intramolecular potentials causes autoionization of an LRMs X₂ towards X₂⁺ + e^-. For the specific case of Cs₂ LRMs, we investigate the vibrational-state distribution of the reaction product Cs₂⁺ by energy-resolved photodissociation using a pulsed mid-IR laser system. In this talk, the results of this study will be presented and analysed in the context of simple reaction models. The prospects for the formation of ultracold pair plasmas via LRMs will be discussed.

[1] M. Peper and J. Deiglmayr, Heteronuclear Long-Range Rydberg Molecules, Phys. Rev. Lett. 126, 013001 (2021)

[2] M. Peper and J. Deiglmayr, Formation of Ultracold Ion Pairs through Long-Range Rydberg Molecules, J. Phys. B: At. Mol. Opt. Phys. 53, 064001 (2020)

[3] M. Peper, M. Trautmann, and J. Deiglmayr, Role of Coulomb Antiblockade in the Photoassociation of Long-Range Rydberg Molecules, Phys. Rev. A 107, 012812 (2023)