The theory of spin exchange between optically pumped alkali-metal atoms and noble-gas nuclei is presented. Spin exchange with heavy noble gases is dominated by interactions in long-lived van der Waals molecules. The main spin interactions are assumed to be the spin-rotation interactions $\gamma \overrightarrow{\mathrm{N}}·\overrightarrow{\mathrm{S}}$ between the rotational angular momentum $\overrightarrow{\mathrm{N}}$ of the alkali-metal—noble-gas pair and the electron spin $\overrightarrow{\mathrm{S}}$ of the alkali-metal atom, and the contact hyperfine interaction $\alpha \overrightarrow{\mathrm{K}}·\overrightarrow{\mathrm{S}}$ between the nuclear spin $\overrightarrow{\mathrm{K}}$ of the noble-gas atom and the electron spin $\overrightarrow{\mathrm{S}}$. Arbitrary values for $K$ and for the nuclear spin $I$ of the alkali-metal atom are assumed. Precise formal expressions for spin transfer coefficients are given along with convenient approximations based on a perturbation expansion in powers of ${\left(\frac{\alpha }{\gamma N}\right)}^2$, a quantity which has been shown to be small by experiment.

• Received 16 December 1983

DOI:https://doi.org/10.1103/PhysRevA.29.3092