DIFFUSION OF MUONIC DEUTERIUM AND HYDROGEN-ATOMS

Diffusion of muonic deuterium mu d and muonic hydrogen mu p atoms prod uced following the stopping of negative muons in D-2 or H-2 at 300 K w as studied at pressures of 47-750 mbar (H-2) and 94-1520 mbar (D?) in two distinct target geometries. Time intervals were recorded between e ntry of negative muons into the gas and arrival of each resulting mu d or mu p atom at one of 50 foils immersed in the gas, and spaced regul arly along the muon beam axis. The results of such measurements were f itted to time distributions generated by Monte Carlo methods, using th eoretical scattering predictions and empirically chosen forms for the initial energy distributions of the muonic atoms in the 1S state. Resu lts indicate muonic atom energy distributions which (a) are different for mu d and mu p and (b) vary with pressure. The best-fit energy dist ributions have mean energies ranging from 1.5 eV for mu d at 94 mbar t o greater than or equal to 9 eV for mu p at 750 mbar. The data are als o sensitive to scattering cross sections for mu d and mu p, and are co nsistent with current theoretical calculations for the mu d+D-2 cross sections. In the case of mu p+H-2 scattering, the experimental data su ggest discrepancies with the theoretical predictions.