Temperature and Magnetic Field Dependence of Three-Body Recombination in Spin-Polarized Hydrogen

The three-body recombination rate in spin-polarized hydrogen has been measured at temperatures from 0.25 to 0.60 K in magnetic fields from 5 to 9 T. In contrast to theoretical expectation, the three-body rate is a weakly decreasing function of field in this region. At 7.6 T the gas and surface three-body rate constants are $L_g=7.5\mathrm{}\left(3\right)\mathrm{}\times {10}^{-39\mathrm{}}$ ${\mathrm{cm}}^6$ ${\mathrm{s}}^{-1\mathrm{}}$ and $L_s=2.0\mathrm{}\left(6\right)\mathrm{}\times {10}^{-24\mathrm{}}$ ${\mathrm{cm}}^4$ ${\mathrm{s}}^{-1\mathrm{}}$. The large value of $L_s$ can account for effects previously attributed to an anomalously large surface two-body nuclear relaxation rate.