H − and D − production by backscattering from alkali-metal targets

Measurements have been made of the total backscattered D -- and H -- yields from thick, clean targets of Cs, Rb, potassium, Na and Li, bombarded with H+2, H+3, D+2, D+3 with incident energies from 0.15 to 4.0 keV/nucleus. For each target, the H -- and D -- yields exhibited max. (as high as 0.08/incident proton and deuteron) at incident energies between 0.3 and 1.4 keV/nucleus. For both hydrogen and deuterium incident at any energy, the negative-ion yield decreases in going from Cs to Li in the order given above. Also, a definite isotope effect was observed for every target used, with the H -- yield peaking at a lower incident energy than the D -- yield and, in most cases, the max. H -- yield was higher than the max. D -- yield. Measurements of the D -- yield as a function of Cs coverage were also made for D+3 bombarding a Ni substrate. The D -- yield maximized at or near the coverage at which the surface work function reached a min.21 refs.--AA