Effective three-body interactions in Cs($6s$)-Cs($nd$) Rydberg trimers

TL;DR

This paper reports the spectroscopic observation of ultralong-range Cs Rydberg trimers, demonstrating effective three-body interactions influenced by atomic anisotropy and relativistic spin effects, supported by theoretical simulations.

Contribution

It provides the first experimental evidence of nonadditive three-body interactions in Rydberg trimers, incorporating relativistic effects into the theoretical model.

Findings

Observation of asymmetric line profiles indicating three-body interactions

Confirmation of nonadditive trimer states coexisting with dimers

Theoretical support including relativistic spin interactions

Abstract

Ultralong-range Rydberg trimer molecules are spectroscopically observed in an ultracold gas of Cs($nd_{3/2}$) atoms. The atomic Rydberg state anisotropy allows for the formation of angular trimer states, whose energies may not be obtained from integer multiples of dimer energies. These nonadditive trimers are predicted to coexist with Rydberg dimer lines. The existence of such effective three-body interactions is confirmed with observation of asymmetric line profiles and interpreted by a theoretical approach which includes relativistic spin interactions. Simulations of the observed spectra with and without angular trimer lines lends convincing support to the existence of effective three-body interactions.