Estimates of the relative magnitudes of the isotropic and anisotropic magnetic-dipole hyperfine interactions in alkali-metal–noble-gas systems

We present a detailed theoretical analysis of the noble-gas nuclear spin relaxation due to the anisotropic magnetic-dipole hyperfine interaction between the noble-gas nucleus and alkali-metal valence electron vis à vis the already well-understood (spin-conserving) isotropic magnetic-dipole hyperfine interaction in alkali-metal–noble-gas systems. We find that, for all pairs in which the noblegas is not helium, the predicted spin relaxation rate from the anisotropic interaction does not exceed 2.5% of the rate from the isotropic interaction, thereby not appreciably limiting the maximum noblegas nuclear polarization attainable via spin-exchange collisions with polarized alkali-metal atoms. For alkali–helium pairs, we predict that the anisotropic interaction has a slightly larger relative effect, perhaps limiting the nuclear polarization to ∼ 95% of the electronic polarization in the RbHe system; however, our confidence in the helium results is limited by a lack of knowledge of the interatomic potentials necessary for the calculation.