Brahms, NathanTscherbul, TimurZhang, PengKlos, JacekSadeghpour, HosseinDalgarno, AlexanderDoyle, JohnWalker, Thad G.2011-09-062010Brahms, Nathan, Timur V. Tscherbul, Peng Zhang, Jacek Klos, Hossein R. Sadeghpour, Alexander Dalgarno, John M. Doyle, and Thad G. Walker. 2010. Formation of van der Waals molecules in buffer-gas-cooled magnetic traps. Physical Review Letters 105:033001.0031-9007http://nrs.harvard.edu/urn-3:HUL.InstRepos:5125274We predict that a large class of helium-containing cold polar molecules form readily in a cryogenic buffer gas, achieving densities as high as 10\(^{12}\)  cm\(^{-3}\). We explore the spin relaxation of these molecules in buffer-gas-loaded magnetic traps and identify a loss mechanism based on Landau-Zener transitions arising from the anisotropic hyperfine interaction. Our results show that the recently observed strong \(T^{-6}\) thermal dependence of the spin-change rate of silver (Ag) trapped in dense \(^{3}\)He is accounted for by the formation and spin change of Ag\(^{3}\)He van der Waals molecules, thus providing indirect evidence for molecular formation in a buffer-gas trap.en-USJournal Article2011-09-0610.1103/PhysRevLett.105.033001