Strong Evidence for Enhanced Multiple Electron Capture from Surfaces in $46\mathrm{MeV}/\mathit{u}$ ${\mathrm{Pb}}^{81+}$ Collisions with Thin Carbon Foils

Strong evidence has been found for enhanced multiple electron capture into $46\mathrm{MeV}/u$ ${\mathrm{Pb}}^{81+}$ with a significant contribution from the entrance surface of thin carbon foils. Capture of up to five electrons has been observed. The multiple electron capture yield is found to increase with decreasing target thickness for thin targets. A simple model describing the data and showing the importance of capture from surfaces is discussed. Further evidence is found for a pronounced asymmetry between electron capture at the entrance and the exit surfaces. Absolute yields for multiple electron capture and projectile ionization are presented. The experimental total cross sections for single capture and ionization agree well with theory.