Campbell, Wesley C.Tscherbul, Timur V.Lu, Hsin-ITsikata, EdemKrems, Roman V.Doyle, John2011-11-212009Campbell, Wesley C., Timur V. Tscherbul, Hsin-I Lu, Edem Tsikata, Roman V. Krems, and John M. Doyle. 2009. Mechanism of collisional spin relaxation in \(^3\)Σ molecules. Physical Review Letters 102(1): 013003.0031-9007http://nrs.harvard.edu/urn-3:HUL.InstRepos:5349606We measure and theoretically determine the effect of molecular rotational splitting on Zeeman relaxation rates in collisions of cold \(^3\)Σ molecules with helium atoms in a magnetic field. All four stable isotopomers of the imidogen (NH) molecule are magnetically trapped and studied in collisions with \(^3\)He and \(^4\)He. The \(^4\)He data support the predicted 1/B\(^{2}_{e}\) dependence of the collision-induced Zeeman relaxation rate coefficient on the molecular rotational constant B\(_e\). The measured \(^3\)He rate coefficients are much larger than the \(^4\)He coefficients, depend less strongly on B\(_e\), and theoretical analysis indicates they are strongly affected by a shape resonance. The results demonstrate the influence of molecular structure on collisional energy transfer at low temperatures.en-USJournal Article2011-11-2110.1103/PhysRevLett.102.013003