Tscherbul, Timur V.Pavlovic, ZoranSadeghpour, HosseinCôté, RobinDalgarno, Alexander2011-09-162010Tscherbul, Timur V., Zoran Pavlovic, Hossein R. Sadeghpour, Robin Côté, and Alexander Dalgarno. 2010. Collisions of trapped molecules with slow beams. Physical Review A 82(2): 022704.1050-2947http://nrs.harvard.edu/urn-3:HUL.InstRepos:5132920We present a theoretical study of molecular-trap loss induced by collisions with slow atomic beams based on an explicit analysis of collision kinematics in the laboratory frame and a rigorous quantum description of atom-molecule scattering in external fields. The theory is applied to elucidate the effects of nonuniform magnetic and optical trapping fields on low-temperature collisions of OH \((J=\frac{3}{2},M_J=\frac{3}{2},f)\) molecules with \(^{4}\)He atoms. Our calculations quantify the extent to which both elastic and inelastic cross sections are suppressed by external trapping fields, clarify the role of small-angle scattering in trap loss, and may benefit future experiments on collisional cooling of molecules in electromagnetic traps. The calculated cross sections for trap loss in \(^{4}\)He + OH collisions are consistent with recent experimental observations at low beam energies [ B. C. Sawyer \(et al.\) Phys. Rev. Lett. 101 203203 (2008)], demonstrating the importance of including the effects of nonuniform trapping fields in theoretical simulations of cold collision experiments with trapped molecules and slow atomic beams.en-USJournal Article2011-09-1610.1103/PhysRevA.82.022704