Tscherbul, Timur V.Klos, JacekDalgarno, AlexanderZygelman, BernardPavlovic, ZoranHummon, Matthew T.Lu, Hsin-ITsikata, EdemDoyle, John2011-09-222010Tscherbul, 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): 042718.1050-2947http://nrs.harvard.edu/urn-3:HUL.InstRepos:5139187We 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.en-USJournal Article2011-09-2210.1103/PhysRevA.82.042718