Recombination and relaxation mechanisms of atomic hydrogen and deuterium at low temperatures and in an ESR spectrometer

The recombination and relaxation mechanisms of atomic hydrogen and atomic deuterium were examined in an ESR spectrometer at temperatures between 0.5 and 0.7 K and a magnetic field of 3 kG. The electronic relaxation time (T1) is weakly dependent on the density and temperature and is felt to be dominated by atomic hydrogen hitting a wall covered with superfluid helium and flipping its spin via an interaction with the ferromagnetic impurities on the microwave cavity wall. From a measurement of the low-temperature flux of atomic deuterium and the known sensitivity of the ESR spectrometer, the assumption that recombination is dominated by the surface leads to a wall recombination coefficient of greater than 5 x 10-11 cm3/sec. Using the accepted value for the adsorption energy of 2.5 K for atomic deuterium on a superfluid surface, the wall recombination cross length is greater than 200 A. This value is two to three order s of magnitude larger than the value for atomic hydrogen. Other loss mechanisms for atomic deuterium are examined