Measured Cross Sections for Photoionization of Ground-State He toHe+(n=2)

Abstract

Cross sections for simultaneous photoionization of He and excitation to ${\mathrm{He}}^{+}$ ($n=2\mathrm{}$) have been measured from threshold to 160 eV. The data show clear evidence of autoionization from levels converging on ${\mathrm{He}}^{+}$ ($n=3\mathrm{}$). Away from such structure, they are in good agreement with previous experimental values. None of the theoretical predictions gives the correct magnitude at low energies.