Formation of Fast Excited H Atoms. III. Collisional Dissociation ofH2+andH3+on Helium

The collisional dissociation of 75- to 700-keV ${\mathrm{H}}_2^{+}$ and ${\mathrm{H}}_3^{+}$ by impact on targets of He is studied. The formation of excited hydrogen is detected by quantitative measurement of collisionally induced Balmer-$\alpha$ emission; the contributions from $3s$, $3p$, and $3d$ levels are separated by a method that utilizes the different lifetime of the excited states. Cross sections are almost the same for each of the $3s$, $3p$, and $3d$ states; they vary slowly with projectile energy.