The absolute photoionization cross section of singly charged magnesium ions in the extreme ultraviolet

Abstract

Absolute photoionization cross sections are presented for Mg + ions in the photon energy range 25-160 eV. The assignments of the structures seen are discussed and compared with earlier assignments derived from photographic measurements. Good agreement is found with theoretical calculations of the continuum cross section, whereas the agreement with calculations of the oscillator strengths and of the line positions is less satisfactory.

Photoionisation cross sections of atomic ions

“…There is no ''pure'' 2p-3d transition; it is merely the dominant configuration in the group of lines around 61 eV in the Mg þ spectrum and 90 eV in the Al 2þ spectrum. The data for Al 2þ are shown in Table 2; in this case the assignments are generally in good agreement with those Kjeldsen et al (2000), . c Assignment for most prominent configuration.…”

“…Such interpretation has relied upon multiconfigurational calculations and, in the absence of any cross section measurements, has focussed on the structure seen in the measurements. With the availability of absolute cross section data and the oscillator strengths that can be calculated from them (Kjeldsen et al, 2000;, some differences in the interpretation have been suggested. The spectral region of interest is that in which the 2p electron is excited, leading to ns and nd autoionising series converging to the 2s 2 2p 5 3s 1 P excited level.…”

“…This prompted a recalculation and revised labelling (Mehlman et al, 1976), with both theoretical results qualitatively in agreement. The ''line'' at 61:31 eV; which in fact contains several lines unresolved in the Aarhus experiment (Kjeldsen et al, 2000), was assigned to transitions to 3s4s 1 S levels. However, given the high oscillator strength contained in this group of lines, it would seem more reasonable to assign it to a transition of the type 2p-3d; as indicated by the RPAE calculations (Ivanov et al, 1994); these did not take configuration interaction into account but there was good agreement between the calculated and measured oscillator strengths.…”

The Absolute Cross Section forL‐Shell Photoionization of C+Ions from Threshold to 105 eV

“…This is also the case for the oscillator strengths of strong and wellresolved peaks, however, the values for weak and/or not fully resolved peaks are larger due to the uncertainties resulting from the peak Ðtting-procedure mentioned above. Further details about the set-up and the determination of the absolute cross section can be found in Kjeldsen et al (1999b), Kjeldsen et al (2000), and Kjeldsen (1999).…”

“…The reason for this situation is that measurements of absolute photoionization cross sections are difficult and so far only a limited number of measurements have been reported ; see Kjeldsen et al (2000). For neutral atoms, the difficulties in the determination of the target-atom density have limited the available data to the noble gases, for which absorption cells can be used, and a few other special cases.…”