Photoionization excitation of helium has been performed employing the R-matrix method with a 20-term target representation for incident photon energies between the $N=2\mathrm{}$ and $N=5\mathrm{}$ thresholds (69–76.8 eV) of the ${\mathrm{He}}^{+}$ ion. Partial differential cross sections for photoionization leaving the ${\mathrm{He}}^{+}$ ion in the $N=2,3,4\mathrm{}$ levels at emission angles $0°$ and in the $N=2\mathrm{}$ level $90°$ are provided. Our results to ${\mathrm{He}}^{+}$ in the $N=2\mathrm{}$ state give fairly good agreement with the available experimental data and theoretical calculations below the $N=3\mathrm{}$ threshold. Between the $N=3\mathrm{}$ and $N=5\mathrm{}$ thresholds of the ${\mathrm{He}}^{+}$ ion, our results for ${\mathrm{He}}^{+}$ in the $N=2,3,4\mathrm{}$ states still agree with experiment qualitatively.

• Received 12 April 1999

DOI:https://doi.org/10.1103/PhysRevA.61.032721