Continuous-wave NMR in spin-polarized atomic hydrogen

Simultaneous continuous-wave NMR and total-pressure measurements on spin-polarized atomic hydrogen gas in a 5-T magnetic field are reported. During sample loading we observe positive nuclear polarization. The rf susceptibility of the decaying sample is nonlinearly related to the density. This and the anomalous NMR line shape are discussed in light of the identical spin-rotation effect and the hydrodynamic spin-wave model. The analysis of the time evolution of the NMR signal area and of the pressure gives the two-body exchange recombination-rate coefficients K/sub a//sub a/ = 1.8 x 10/sup -19/ cm3 s/sup -1/ and K/sub a//sub b/ = 1.6 x 10/sup -19/ cm3 s/sup -1/, and the one-body relaxation rate G1 = 1 x 10/sup -4/ s/sup -1/ in the absence of rf field, at T = 370 mK