Nolte, JeffYang, B.H.Stancil, PhillipLee, Teck-GheeBalakrishnan, NaduvalathForrey, Robert C.Dalgarno, Alexander2011-09-122010Nolte, Jeff L., B.H. Yang, Phillip C. Stancil, Teck-Ghee Lee, Naduvalath Balakrishnan, Robert C. Forrey, and Alexander Dalgarno. 2010. Isotope effects in complex scattering lengths for He collisions with molecular hydrogen. Physical Review A 81(1): 014701.1050-2947http://nrs.harvard.edu/urn-3:HUL.InstRepos:5128487We examine the effect of theoretically varying the collision-system reduced mass in collisions of He with vibrationally excited molecular hydrogen and observe zero-energy resonances for select atomic “hydrogen” masses less than 1 u or a “helium” mass of 1.95 u. Complex scattering lengths, state-to-state vibrational quenching cross sections, and a low-energy elastic scattering resonance are all studied as a function of collision-system reduced mass. Experimental observations of these phenomena in the cold and ultracold regimes for collisions of \(^{3}\)He and \(^{4}\)He with H\(_{2}\), HD, HT, and DT should be feasible in the near future.en-USJournal Article2011-09-1210.1103/PhysRevA.81.014701