Angular distributions forH−formation in single collisions ofH+on Mg

Absolute differential cross sections have been measured for ${\mathrm{H}}^{-}$ formation in single collisions of ${\mathrm{H}}^{+}$ on Mg in the energy range from 0.5 to 5.0 keV. Total cross sections, obtained by direct integration of these differential cross sections, are in good agreement with earlier total-cross-section measurements of Morgan and Eriksen in the energy range common to the two experiments and are in good agreement with the calculated total cross sections of Olson and Liu. The differential cross sections are strongly peaked in the forward direction. The functional form and scaling properties of this forward peak strongly indicate that it is a glory maximum, which occurs when the classical deflection function changes over from attractive to repulsive at some finite impact parameter. The differential cross sections from 1.0 to 5.0 keV show no other structure, but below 1.0 keV a $\tau$-dependent structure is observed which becomes more pronounced as the collision energy decreases. 1982 The American Physical Society.