AN EXPERIMENTAL-METHOD FOR EVALUATING THE H-2 AND D-2 CONTAMINATION LEVELS IN A HD BOTTLE

Studies of one- and two-electron processes in collisions with hydrogen molecules using the time-of-flight technique are simplified by using the heteronuclear HD isotope because the H+ and D+ fragments can be ea sily distinguished from each other. The difference in the time-of-flig ht of H+ and D+ enable the fragments to be measured in coincidence wit h each other. However, it is hard to determine the purity of the HD ta rget, in particular the H-2 contamination, because the H-2(+) molecula r ions coincide with the D+ fragments. A method is suggested to determ ine the purity of a HD target to a precision of a few percent. This me thod is based on measuring the yield of very slow (< 0.5 eV) H+ and D fragments of HD bombarded by fast protons (E > 1 MeV). The H-2 contam ination is then determined by subtracting the theoretically evaluated contribution of the ground-state dissociation of the HD+ molecular ion from the measured sum of both H+ and D+ low-energy fragments.