Phase protection of Fano-Feshbach resonances

Abstract

Decay of bound states due to coupling with free particle states is a general phenomenon occurring at energy scales from MeV in nuclear physics to peV in ultracold atomic gases. Such a coupling gives rise to Fano-Feshbach resonances (FFR) that have become key to understanding and controlling interactions - in ultracold atomic gases, but also between quasiparticles such as microcavity polaritons. The energy positions of FFR were shown to follow quantum chaotic statistics. In contrast, lifetimes which are the fundamental property of a decaying state, have so far escaped a similarly comprehensive understanding. Here we show that a bound state, despite being resonantly coupled to a scattering state, becomes protected from decay whenever the relative phase is a multiple of $\pi$. We observe this phenomenon by measuring lifetimes spanning four orders of magnitude for FFR of spin-orbit excited molecular ions with merged beam and electrostatic trap experiments. Our results provide a blueprint for identifying naturally long-lived states in a decaying quantum system.

References in corpus (6)

• Feshbach Resonances in Ultracold Gases
• Observation of Quantum Effects in sub Kelvin Cold Reactions
• Quantum Chaos in Ultracold Collisions of Erbium
• Spontaneous Dissociation of 85Rb Feshbach Molecules
• Spontaneous dissociation of long-range Feshbach molecules
• Evaporation of buffer gas-thermalized anions out of a multipole rf ion trap

Cited by in corpus (4)

• Determining the nature of quantum resonances by probing elastic and reactive scattering in cold collisions
• The quantum and classical Fano parameter $q$
• Direct Observation of a Feshbach-resonance by Coincidence-detection of Ions and Electrons in Penning Ionization Collisions
• Scattering Angle Dependence of Fano Resonance Profiles in Cold Atomic Collisions Analyzed with the Complex Valued $w$ Parameter