Molecular physics and finite-range effects : feshbach resonances in ultracold gas

We study collisions in an optically trapped, pure sample of ultracold Cs 2 molecules in various internal states. The molecular gas is created by Feshbach association from a near-degenerate atomic gas, with adjustable temperatures in the nanokelvin range. We identify several narrow loss resonances, which point to the coupling to more complex molecular states and may be interpreted as Feshbach resonances in dimerdimer interactions. Moreover, in some molecular states we observe a surprising temperature dependence in collisional loss. This shows that the situation cannot be understood in terms of the usual simple threshold behavior for inelastic two-body collisions. We interpret this observation as further evidence for a more complex molecular structure beyond the well-understood dimer physics.We study collisions in an optically trapped, pure sample of ultracold Cs 2 molecules in various internal states. The molecular gas is created by Feshbach association from a near-degenerate atomic gas, with adjustable temperatures in the nanokelvin range. We identify several narrow loss resonances, which point to the coupling to more complex molecular states and may be interpreted as Feshbach resonances in dimerdimer interactions. Moreover, in some molecular states we observe a surprising temperature dependence in collisional loss. This shows that the situation cannot be understood in terms of the usual simple threshold behavior for inelastic two-body collisions. We interpret this observation as further evidence for a more complex molecular structure beyond the well-understood dimer physics.

arXiv:0904.0935Laser PhysicsJul 29, 200913 citations

Feshbach Resonances and Medium Effects in Ultracold Atomic Gases

Georg M. Bruun

arXiv:0903.4858Few-Body SystemsFeb 19, 20096 citations

Two-Body Contact Dynamics in a Bose Gas near a Fano-Feshbach Resonance

Alexandre Journeaux, Julie Veschambre, Maxime Lecomte +5 more

We investigate the real-time buildup of short-range correlations in a nondegenerate ultracold Bose gas near a narrow Fano-Feshbach resonance. Using rapid optical control, we quench the closed-channel molecular energy to resonance on submicrosecond timescales and track the evolution of the two-body contact through photodissociation losses. Repeated pulse sequences enhance sensitivity to early-time two-body losses and reveal long-lived coherence between atom pairs and molecular states. The observed dynamics are accurately reproduced by our dynamical two-channel zero-range theory, which explicitly accounts for the resonance's narrow width and finite closed-channel decay, establishing a predictive framework for correlation dynamics in quantum gases near Fano-Feshbach resonances.We investigate the real-time buildup of short-range correlations in a nondegenerate ultracold Bose gas near a narrow Fano-Feshbach resonance. Using rapid optical control, we quench the closed-channel molecular energy to resonance on submicrosecond timescales and track the evolution of the two-body contact through photodissociation losses. Repeated pulse sequences enhance sensitivity to early-time two-body losses and reveal long-lived coherence between atom pairs and molecular states. The observed dynamics are accurately reproduced by our dynamical two-channel zero-range theory, which explicitly accounts for the resonance's narrow width and finite closed-channel decay, establishing a predictive framework for correlation dynamics in quantum gases near Fano-Feshbach resonances.

arXiv:2509.03567Physical Review LettersJan 26, 20264 citations

Theory of Ultracold Feshbach Molecules

Thomas M. Hanna, Hugo E. L. Martay, Thorsten Köhler

Jun 25, 20091 citation

Approach to form long-range ion-pair molecules in an ultracold Rb gas

Adam Kirrander, Seth T. Rittenhouse, Marco Ascoli +3 more

We propose a realizable and efficient approach for exciting long-range ion-pair molecules, known as heavy Rydberg states, in an ultracold ${}^{85}$ Rb gas via Feshbach resonances. Heavy Rydberg states, the molecular analogs of electronic Rydberg states, with the electron replaced by an atomic anion, offer opportunities for novel physics, including the formation of ultracold anions and strongly coupled plasmas. We map the positions, lifetimes, and Franck-Condon factors of heavy Rydberg resonances across a wide range of excitation energies, and we calculate the rates of formation for the most promising transitions through long-lived intermediate interferometric resonances.We propose a realizable and efficient approach for exciting long-range ion-pair molecules, known as heavy Rydberg states, in an ultracold ${}^{85}$Rb gas via Feshbach resonances. Heavy Rydberg states, the molecular analogs of electronic Rydberg states, with the electron replaced by an atomic anion, offer opportunities for novel physics, including the formation of ultracold anions and strongly coupled plasmas. We map the positions, lifetimes, and Franck-Condon factors of heavy Rydberg resonances across a wide range of excitation energies, and we calculate the rates of formation for the most promising transitions through long-lived intermediate interferometric resonances.

Physical Review AMar 22, 201320 citations

We propose a realizable and efficient approach for exciting long-range ion-pair molecules, known as heavy Rydberg states, in an ultracold

{}^{85}

Rb gas via Feshbach resonances. Heavy Rydberg states, the molecular analogs of electronic Rydberg states, with the electron replaced by an atomic anion, offer opportunities for novel physics, including the formation of ultracold anions and strongly coupled plasmas. We map the positions, lifetimes, and Franck-Condon factors of heavy Rydberg resonances across a wide range of excitation energies, and we calculate the rates of formation for the most promising transitions through long-lived intermediate interferometric resonances.