Decay Paths of Interfering Two-Electron Excitations in Helium

Abstract

Partial photoionization cross sections and photoelectron angular distributions of He in the region of interfering Rydberg series below the $n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}5$ threshold are measured and compared with theoretical results based on the hyperspherical close-coupling method. At a bandpass of $12\mathrm{meV}$ for the photon energy, this level of differentiation offers the most critical assessment of the dynamics of the two-electron excitations to date. A good understanding is achieved.