HYPERFINE RESONANCE OF GASEOUS ATOMIC-HYDROGEN AT 4.2-K

We have measured the hyperfine frequency and wall shift of hydrogen atoms at 4.2 K stored in a bulb coated with solid H2. The phase shift per wall collision is - 0.29(1) rad. The adsorption energy of H on H2 is 9(2) K, and the adsorption time at 4.2 K is approximately 30 nsec. Transverse and longitudinal relaxation times have been measured, and atomic densities greater than 1014/cm3 have been observed. © 1979 The American Physical Society.