Complete description of 3p photoionization in calcium

Abstract

Abstract. Within the dipole approximation and the LS-coupling limit 3p photoionization in atomic calcium is described completely by two matrix elements and one relative phase. These three parameters are extracted from experimental observables and compared with theoretical calculations (RRPA transformed to the non-relativistic limit) for photon energies around the Cooper minimum in the 3p → d channel. Taking into account the intensity-borrowing model, excellent agreement between theoretical and experimental data is found.

Dipole matrix elements for 4p photoionization of Sr

“…In fact, when the coincidence analysis is run with the errors in A i increased by up to ten times, the (Cooper 1962) at hν = 59 eV; the dipole moment for the 4p → d channel goes through zero at this energy. This has been seen experimentally by Lörch et al (1999) and predicted theoretically in our previous paper (De Fanis et al 1999). For the case of Kr, measurements of the photoionization cross section (West and Marr 1976) indicate the presence of a Cooper minimum at a photon energy of ∼80 eV; from this it could be anticipated that a Cooper minimum for 4p photoionization of Sr would also be in this region, which is consistent with the slower increase in the ratio |D s /D d | over the range of our measurements in comparison with the case for Ca.…”

“…These results were compared with a RPAE calculation; the conclusion was that the LSJ coupling scheme for the process investigated was entirely appropriate. The work of De Fanis et al (1999) extended towards threshold the results of Lörch et al (1999), the latter covered the range hν = 45-95 eV.…”

Photoionization of atomic ions

“…In a few isolated cases heat pipes have been used to contain the vapour (see, e.g., Codling et al 1977, Mehlman et al 1978, Ederer et al 1979, Chu et al 1998. For other atoms the cross sections have been either inferred using sum rules (Jannitti et al 1984b) or calibrated against a photoline of known cross section in an electron spectroscopy experiment (Lörch et al 1999). Such procedures are prone to systematic errors, and it is difficult to be sure of the accuracy of the final result, where ±10% is the aim but rarely achieved in practice.…”

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

“…Measurements of the absolute photoionization cross sections of atoms are rare in the literature, largely because of the difficulty in determining the atomic density in a photoabsorption experiment. Apart from the noble gases, for which an absorption cell can be used since the pressure can be measured sufficiently accurately, and isolated cases where heat pipes can be applied for metal vapours (Codling et al 1977, Mehlman et al 1978, Chu et al 1998 the cross sections for other atoms are either inferred using sum rules (Janitti et al 1984) or calibrated against a photoline of known cross section in an electron spectroscopy experiment (Lörch et al 1999). Such procedures are prone to systematic errors, and it is difficult to be sure of the accuracy of the final result.…”