Charge Exchange in Proton-Hydrogen-Atom Collisions

The charge-exchange cross sections for the reactions $p+\mathrm{H}\to \mathrm{H}+p$, and ${{\mathrm{H}}_2}^{+}+\mathrm{H}\to {\mathrm{H}}_2+p$ have been examined over the energy range 200 to 14 000 ev. In the experiment a dc fast-ion beam crossed a slow atomic hydrogen beam which was chopped at 100 cps. The desired signal thus was separable from the much larger signal arising from interaction of the ions with the residual gas in the vacuum chamber, because the signal arising from the interaction of the two beams occurred at the chopping frequency and in a specified phase. The signals used were the saturated slow-ion currents, recorded at a detector which did not discriminate the ion mass, and the slow-ion currents after mass analysis. The measured values at high energies agree very satisfactorily with the Born approximation calculations by Bates and Dalgarno and, at low energies, with calculations by Dalgarno and Yadav using the method of perturbed stationary states. Experimental comparison of cross sections for proton and deuteron collisions is presented.