K-shell ionization probabilities of Pb at small impact parameters by 25-, 40-, and 74-MeVαparticles

Abstract

The absolute $K$-shell ionization probabilities of Pb at very small impact parameters by 25-, 40-, and 74-MeV $\ensuremath{\alpha}$ particles are measured in an $\ensuremath{\alpha}$-x-ray coincidence experiment, using the slight inelasticity of the scattered $\ensuremath{\alpha}$ particles. Ionization probabilities are (1.9 \ifmmode\pm\else\textpm\fi{} 0.4) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}4}$, (4.9 \ifmmode\pm\else\textpm\fi{} 1.7) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}4}$, and (11 \ifmmode\pm\else\textpm\fi{} 3) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}4}$ at 25, 40, and 74 MeV, respectively. Semiclassical calculations, using relativistic electron wave functions and corrections for Coulomb deflection effects, agree very well with the data. Possible quantitative studies of atomic distortion effects are suggested.