Elliptic Polarization of Balmer Radiation from Low-Energy Grazing-Incidence Collisions of Hydrogen Ions on Surfaces

Abstract

Pronounced elliptic polarization has been observed in Balmer radiation following low-energy grazing-incidence collisions of ${\mathrm{H}}^{-}$, ${\mathrm{H}}^{+}$, ${\mathrm{H}}_2^{+}$, and ${\mathrm{H}}_3^{+}$ on a clean lead surface maintained under ultrahigh vacuum. The polarization, shown to arise predominantly from $p$ states, is found to depend only on velocity, not on the charge or molecular species of the incoming projectile. A two-step surface-interaction model is presented based on anisotropic near-resonant electron pickup followed by quantum mechanical phase evolution.