Cold and ultracold NH--NH collisions: The field-free case

Abstract

We present elastic and inelastic spin-changing cross sections for cold and ultracold NH($X{}^3{\Sigma }^{-}$) + NH($X{}^3{\Sigma }^{-}$) collisions, obtained from full quantum scattering calculations on an accurate \textit{ab initio} quintet potential-energy surface. Although we consider only collisions in zero field, we focus on the cross sections relevant for magnetic trapping experiments. It is shown that evaporative cooling of both fermionic ${}^{14}$NH and bosonic ${}^{15}$NH is likely to be successful for hyperfine states that allow for s-wave collisions. The calculated cross sections are very sensitive to the details of the interaction potential, due to the presence of (quasi-)bound state resonances. The remaining inaccuracy of the \textit{ab initio} potential-energy surface therefore gives rise to an uncertainty in the numerical cross-section values. However, based on a sampling of the uncertainty range of the \textit{ab initio} calculations, we conclude that the exact potential is likely to be such that the elastic-to-inelastic cross-section ratio is sufficiently large to achieve efficient evaporative cooling. This likelihood is only weakly dependent on the size of the channel basis set used in the scattering calculations.

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Cited by in corpus (11)

• Quantum reactive scattering of ultracold NH($X{}^3{\Sigma }^{-}$) radicals in a magnetic trap
• The prospects of sympathetic cooling of NH molecules with Li atoms
• Efficient method for quantum calculations of molecule - molecule scattering properties in a magnetic field
• The effect of hyperfine interactions on ultracold molecular collisions: NH(^3Sigma^-) with Mg(^1S) in magnetic fields
• Universal probability distributions of scattering observables in ultracold molecular collisions
• Molecular Collisions: from Near-cold to Ultra-cold
• Multistage Zeeman deceleration of NH $X{}^3{\Sigma }^{-}$ radicals
• On the role of the magnetic dipolar interaction in cold and ultracold collisions: Numerical and analytical results for NH(${}^3{\Sigma }^{-}$) + NH(${}^3{\Sigma }^{-}$)
• Elastic and inelastic collisions of ${}^2\Sigma$ molecules in a magnetic field
• Magnetic Feshbach resonances in collisions of non-magnetic closed-shell ${}^1\Sigma$ molecules
• Hyperfine and Zeeman interactions in ultracold collisions of molecular hydrogen with atomic lithium