Magnetic decoupling of ¹²⁹Xe-Rb and ¹²⁹Xe-Cs binary spin exchange

We report calculations of the magnetic decoupling of the nuclear spin relaxation rate of ¹²⁹Xe atoms caused by binary collisions with Rb or Cs atoms in a gas. A semiclassical approximation, using a classical path for the collision and treating the spin interactions quantum mechanically, gives results that differ by no more than 2% from calculations with the distorted-wave Born approximation. Both computational methods show that the relaxation rate decreases substantially for magnetic fields of a few tens of teslas. For ¹²⁹Xe-Rb, where recent experimental measurements are available, the calculated rate coefficients at the experimental field of 9.4 T are about 80% of the calculated values at zero field. At 9.4 T, the calculated rate coefficient for ¹²⁹Xe-Rb is about one-half of the experimentally observed value. This discrepancy is probably due to inaccuracies in the van der Waals and spin-dependent potentials used in the calculations.