Theory of Spin Relaxation and Recombination in Spin-Polarized Atomic Hydrogen

A calculation is presented of the relaxation rate T1-1 between the lowest two hyperfine states of a dilute gas of H atoms in high magnetic field at low temperatures. Dipole-dipole interactions dominate T1-1, leading to long relaxation times at low temperatures (T1-1≈10-2nHT12 sec-1 at H≈100 kG). The recombination rate due to wall collisions is much greater than T1-1 and can lead to a depletion of the lowest hyperfine state from thermal equilibrium and an effective recombination rate equal to T1-1.