Collisional properties of cold spin-polarized nitrogen gas: theory, experiment, and prospects as a sympathetic coolant for trapped atoms and molecules

Abstract

We report a combined experimental and theoretical study of collision-induced dipolar relaxation in a cold spin-polarized gas of atomic nitrogen (N). We use buffer gas cooling to create trapped samples of 14N and 15N atoms with densities 5+/-2 x 10^{12} cm-3 and measure their magnetic relaxation rates at milli-Kelvin temperatures. Rigorous quantum scattering calculations based on accurate ab initio interaction potentials for the 7Sigma_u electronic state of N2 demonstrate that dipolar relaxation in N + N collisions occurs at a slow rate of ~10^{-13} cm3/s over a wide range of temperatures (1 mK to 1 K) and magnetic fields (10 mT to 2 T). The calculated dipolar relaxation rates are insensitive to small variations of the interaction potential and to the magnitude of the spin-exchange interaction, enabling the accurate calibration of the measured N atom density. We find consistency between the calculated and experimentally determined rates. Our results suggest that N atoms are promising candidates for future experiments on sympathetic cooling of molecules.

48 pages, 17 figures, 3 tables

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Cited by in corpus (8)

• Cold N+NH Collisions in a Magnetic Trap
• Cold collisions of N atoms and NH molecules in magnetic fields
• Atom-molecule collisions, spin relaxation, and sympathetic cooling in an ultracold spin-polarized Rb(${}^2\mathrm{S}$)-SrF${(}^2{\Sigma }^{+})$ mixture
• Magnetically tunable Feshbach resonances in Li+Er
• First-order symmetry-adapted perturbation theory for multiplet splittings
• On the role of the magnetic dipolar interaction in cold and ultracold collisions: Numerical and analytical results for NH(${}^3{\Sigma }^{-}$) + NH(${}^3{\Sigma }^{-}$)
• Long-range interactions between ultracold atoms and molecules including atomic spin-orbit
• Cold collisions of an open-shell S-state atom with a ^2Pi molecule: N(^4S) colliding with OH in a magnetic field