# Collisional Properties of Cold Spin-Polarized Nitrogen Gas: Theory, Experiment, and Prospects as a Sympathetic Coolant for Trapped Atoms and Molecules

 Title: Collisional Properties of Cold Spin-Polarized Nitrogen Gas: Theory, Experiment, and Prospects as a Sympathetic Coolant for Trapped Atoms and Molecules Author: Tscherbul, Timur V.; Dalgarno, Alexander; Klos, Jacek; Zygelman, Bernard; Pavlovic, Zoran; Hummon, Matthew T.; Lu, Hsin-I; Doyle, John M.; Tsikata, Edem Note: Order does not necessarily reflect citation order of authors. Citation: Tscherbul, Timur V., Jacek Klos, Alexander Dalgarno, Bernard Zygelman, Zoran Pavlovic, Matthew T. Hummon, Hsin-I Lu, Edem Tsikata, and John M. Doyle. 2010. Collisional properties of cold spin-polarized nitrogen gas: Theory, experiment, and prospects as a sympathetic coolant for trapped atoms and molecules. Physical Review A 82(4): 042718. Full Text & Related Files: Dalgarno_Collisional.pdf (1.014Mb; PDF) 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 $$^{14}$$N and $$^{15}$$N atoms with densities (5$$\pm$$2) × $$10^{12}$$ $$cm^{-3}$$ and measure their magnetic relaxation rates at milli-Kelvin temperatures. These measurements, together with rigorous quantum scattering calculations based on accurate $$ab$$ $$initio$$ interaction potentials for the $$^{7}\Sigma^{+}_{u}$$ electronic state of $$N_{2}$$ demonstrate that dipolar relaxation in N+N collisions occurs at a slow rate of ~$$10^{-13}$$ $$cm^{3}$$/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. Published Version: doi:10.1103/PhysRevA.82.042718 Other Sources: http://arxiv.org/abs/1007.0469 Terms of Use: This article is made available under the terms and conditions applicable to Other Posted Material, as set forth at http://nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of-use#LAA Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:5139187 Downloads of this work: