Ultracold atom-molecule collisions and bound states in magnetic fields: tuning zero-energy Feshbach resonances in He-NH (3Sigma-)

Abstract

We have generalized the BOUND and MOLSCAT packages to allow calculations in basis sets where the monomer Hamiltonians are off-diagonal and used the new capability to carry out bound-state and scattering calculations on 3He-NH and 4He-NH as a function of magnetic field. Following the bound-state energies to the point where they cross thresholds gives very precise predictions of the magnetic fields at which zero-energy Feshbach resonances occur. We have used this to locate and characterize two very narrow Feshbach resonances in 3He-NH. Such resonances can be used to tune elastic and inelastic collision cross sections, and sweeping the magnetic field across them will allow a form of quantum control in which separated atoms and molecules are associated to form complexes. For the first resonance, where only elastic scattering is possible, the scattering length shows a pole as a function of magnetic field and there is a very large peak in the elastic cross section. For the second resonance, however, inelastic scattering is also possible. In this case the pole in the scattering length is dramatically suppressed and the cross sections show relatively small peaks. The peak suppression is expected to be even larger in systems with stronger inelasticity. The results suggest that calculations on ultracold molecular inelastic collisions may be much less sensitive to details of the potential energy surface than has been believed.

14 pages, 13 figures Version 2 has clarified (slightly extended) discussion in sections 2C and 2D, exact forms of Eqs. 23 and 24 (new numbering) and some extra references. A few minor typographical errors have also been corrected

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• Towards the production of ultracold ground-state RbCs molecules: Feshbach resonances, weakly bound states, and coupled-channel model
• MOLSCAT: a program for non-reactive quantum scattering calculations on atomic and molecular collisions
• Feshbach resonances in ultracold atomic and molecular collisions: threshold behaviour and suppression of poles in scattering lengths
• Ultracold RbSr molecules can be formed by magnetoassociation
• Feshbach resonances, weakly bound molecular states and coupled-channel potentials for cesium at high magnetic fields
• Production of ultracold NH molecules by sympathetic cooling with Mg
• Magnetically tunable Feshbach resonances in ultracold Li-Yb mixtures
• The prospects of forming ultracold molecules in ${}^2\Sigma$ states by magnetoassociation of alkali-metal atoms with Yb
• Interactions and dynamics in Li + Li_2 ultracold collisions
• Contrasting the wide Feshbach resonances in ${}^6$Li and ${}^7$Li
• Generating mesoscopic Bell states via collisions of distinguishable quantum bright solitons
• Multichannel Quantum Defect Theory for cold molecular collisions
• The prospects of sympathetic cooling of NH molecules with Li atoms
• Feshbach resonances in ultracold 85Rb
• BOUND and FIELD: programs for calculating bound states of interacting pairs of atoms and molecules
• Cold and ultracold NH--NH collisions in magnetic fields
• The prospects for producing ultracold NH${}_3$ molecules by sympathetic cooling: a survey of interaction potentials
• Tuning bimolecular chemical reactions by electric fields
• Cold collisions of N atoms and NH molecules in magnetic fields
• Observation of interspecies Feshbach resonances in an ultracold ${}^{39}$K-${}^{133}$Cs mixture and refinement of interaction potentials
• Dramatic reductions in inelastic cross sections for ultracold collisions near Feshbach resonances
• Feshbach spectroscopy of an ultracold mixture of ${}^{85}$Rb and ${}^{133}$Cs
• The effect of hyperfine interactions on ultracold molecular collisions: NH(^3Sigma^-) with Mg(^1S) in magnetic fields
• Magnetically tunable Feshbach resonances in Li+Er
• Cold and ultracold NH--NH collisions: The field-free case
• Feshbach resonances, molecular bound states and prospects of ultracold molecule formation in mixtures of ultracold K and Cs
• Loss of molecules in magneto-electrostatic traps due to nonadiabatic transitions
• Characterizing Feshbach resonances in ultracold scattering calculations
• Optimized Multichannel Quantum Defect Theory for cold molecular collisions
• Quantum chaos in ultracold collisions between Yb(${}^1$S${}_0$) and Yb(${}^3$P${}_2$)
• On the role of the magnetic dipolar interaction in cold and ultracold collisions: Numerical and analytical results for NH(${}^3{\Sigma }^{-}$) + NH(${}^3{\Sigma }^{-}$)
• Total angular momentum representation for atom-molecule collisions in electric fields
• Sympathetic cooling of fluorine atoms with ultracold atomic hydrogen
• Greatly enhanced absorption of non-resonant microwave fields by ultracold molecules near a Feshbach resonance
• Selective quantum Zeno effect of ultracold atom-molecule scattering in dynamic magnetic fields
• Zeeman relaxation of MnH (X7Σ+) in collisions with 3He: mechanism and comparison with experiment
• Elastic and inelastic collisions of ${}^2\Sigma$ molecules in a magnetic field
• Multichannel Quantum Defect Theory for cold molecular collisions with a strongly anisotropic potential energy surface
• Entangling two distinguishable quantum bright solitons via collisions
• Restricted basis set coupled-channel calculations on atom-molecule collisions in magnetic fields
• Theoretical study of the quenching of NH (singlet Delta) molecules via collisions with Rb atoms: preliminary results
• Rotational predissociation of extremely weakly bound atom-molecule complexes produced by Feshbach resonance association