Simultaneous Photoionization and Photoexcitation of Helium

A general method is presented for calculating the $f$ values for all permitted dipole transitions involving simultaneous photoionization and photoexcitation of helium. The cross section for ions excited into the $n=2\mathrm{}$ state is compared with experiment and with a similar calculation by Salpeter and Zaidi; their result, that the ejected electron is in a $p$ state is confirmed. The probability for the residual ${\mathrm{He}}^{+}$ ion to be excited to a state of principle quantum number $n$ is evaluated for $n=2-10\mathrm{}$, and the probability for the photoelectron to be in a $p$ state is compared with the probability for it to be emitted in an $s$ state. It is found that the inclusion of contributions from simultaneous photoionization and photoexcitation, and from double ionization in the total helium photoionization cross section, improves the agreement between theory and the experimental data at high energies.