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Long-range states in collisions of ultracold molecules

James F. E. Croft1, Brian K. Kendrick2, and Jeremy M. Hutson1,*

  • 1Joint Quantum Centre (JQC) Durham-Newcastle, Department of Chemistry, Durham University, South Road, Durham DH1 3LE, United Kingdom
  • 2Theoretical Division (T-1, MS B221), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

  • *Contact author: j.m.hutson@durham.ac.uk
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Phys. Rev. Research 8, 043087 – Published 23 October, 2026

DOI: https://doi.org/10.1103/fvjz-ymg4

Abstract

We use coupled-channel calculations to explore the nature of near-threshold bound states in a simplified model of Rb+KRb. This is a prototype for systems with very strong coupling at short range and chaotic behavior for the short-range states. We find that there are states with strong long-range character that exist close to threshold and probably persist to depths at least 100 GHz below each threshold. These states are only weakly coupled to the short-range states and do not form part of the chaotic manifold. Since they spend little time at short range, they are relatively insensitive to destruction by laser light. They can thus have long lifetimes that are unrelated to the density of states and can cause narrow Feshbach resonances when the states are shifted across thresholds by external fields.

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Phys. Rev. Research 8, 043087– Published 23 October, 2026
  • Received 1 May 2026
  • Accepted 2 October 2026
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