Cold N+NH Collisions in a Magnetic Trap

We present an experimental and theoretical study of atom-molecule collisions in a mixture of cold, trapped atomic nitrogen and NH molecules at a temperature of $sim 600$~mK. We measure a small N+NH trap loss rate coefficient of $k^{(mathrm{N+NH})}_mathrm{loss} = 8(4) times 10^{-13}$~cm$^{3}$s$^{-1}$. Accurate quantum scattering calculations based on {it ab initio} interaction potentials are in agreement with experiment and indicate the magnetic dipole interaction to be the dominant loss mechanism. Our theory further indicates the ratio of N+NH elastic to inelastic collisions remains large ($>100$) into the mK regime.

Low-energy inelastic collisions of OH radicals with He atoms and D$_2$ molecules

We present an experimental study on the rotational inelastic scattering of OH ($X^2Pi_{3/2}, J=3/2, f$) radicals with He and D$_2$ at collision energies between 100 and 500 cm$^{-1}$ in a crossed beam experiment. The OH radicals are state selected and velocity tuned using a Stark decelerator. Relative parity-resolved state-to-state inelastic scattering cross sections are accurately determined. These experiments complement recent low-energy collision studies between trapped OH radicals and beams of He and D$_2$ that are sensitive to the total (elastic and inelastic) cross sections (Sawyer emph{et al.}, emph{Phys. Rev. Lett.} textbf{2008}, emph{101}, 203203), but for which the measured cross sections could not be reproduced by theoretical calculations (Pavlovic emph{et al.}, emph{J. Phys. Chem. A} textbf{2009}, emph{113}, 14670). For the OH-He system, our experiments validate the inelastic cross sections determined from rigorous quantum calculations.