Abstract. We have used angle-resolved photoelectron spectroscopy and improved R-matrix calculations to study the (n = 3 - 5) autoionizing resonances and the doubly excited resonance in the photon energy range between 44 and 48.5 eV. The photoelectrons were detected at different angles using three time-of-flight spectrometers. The measurements were obtained utilizing the 18 meV photon energy resolution provided by an undulator coupled with a spherical grating monochromator of the Advanced Light Source. Angular distribution parameters of these resonances have been parametrized using a model by Kabachnik and Sazhina and have been compared with our R-matrix calculations which are similar to those of Burke and Taylor. We find that the calculations agree quite well with the measurements. Our analysis of the cross section shape shows no strong n dependence of the q and parameter, while the width varies as the quantum defect theory predicts. Also, the differential cross section parameters agree well with previous experiments carried out for the lower resonances.

Print publication: Issue 3 (14 February 1997)
Received 9 September 1996