The theory of spin-polarized ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ relaxation due to hyperfine coupling in ${}_{}{}^3{}_{}{}^{}$${\mathrm{He}}^{+}$ is presented. Comparison is made between the theory and recent experiments which utilized spin-polarized ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ as a charged-particle-beam target. At high He pressures the relaxation rate decreases with pressure. In addition, charge-transfer processes with foreign gases suppress ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ depolarization by reducing the ${}_{}{}^3{}_{}{}^{}$${\mathrm{He}}^{+}$ concentration.

• Received 26 May 1988

DOI:https://doi.org/10.1103/PhysRevA.38.4481