Electron-spin-resonance studies of spin-polarized hydrogen on the surface of liquid He4

Electron-spin resonance at 114 GHz is used to measure the three-body recombination rate (L3) and the two-body surface relaxation rate (G2s) for doubly-spin-polarized H between 100 and 200 mK. Our results for L3 confirm and extend those of Cline, Greytak, and Kleppner. We find that G2s is much smaller than previously reported and in reasonable agreement with theory. Around 100 mK, we also observe sidebands due to surface atoms whose frequency is shifted by dipole-dipole interactions.