THE 2ND-ORDER RECOMBINATION AND SPIN-EXCHANGE RELAXATION OF ATOMIC DEUTERIUM AT LOW-TEMPERATURES IN A LOW MAGNETIC-FIELD

We measured the 2nd order tecombination rates and spin-exchange relaxa tion of atomic deuterium (D) in a He-4 coated sample cell, using the h yperfine resonance of beta(F = 1/2, m(F) = - 1/2) - delta(F = 3/2, m(F ) = - 1/2) transition in a low magnetic field (3.9 mT) at temperatures between 0.6 K and 1.2 K. At lower temperatures below 0.9 K, the densi ty decay of D atoms was dominated by D-D recombination on the liquid H e surface. We found that the surface recombination cross length was 1( DD) = (5.5 +/- 1.3) x 10(-9) cm and the adsorption energy of D on He-4 surface was epsilon(a) = 3.97 +/- 0.07 K. Compared with prior measure ments at high magnetic fields by other groups, 1(DD) at low field was orders of magnitude smaller than what was expected when the scaling of 1/B-2 dependence of the direct recombination mechanism? was used and in addition, epsilon(a) was significantly larger. This I vas attribute d to the onset of rite resonant recombination mechanism for the D-D su rface recombination at high fields. Above 0.9 K, D-D volume recombinat ion and recombination of D with hydrogen impurity, became dominant pro cesses of rite density decay of D. The transverse relaxation times wer e measured and we determined the D-D spin-exchange relaxation rates, G (DD) = (1.4 +/- 0.6) x 10(-10) cm(3) sec(-1) It was smaller than theor etical calculations.