Absolute cross sections for L-shell photoionization of the ions N$\mathsf{^{2+}}$, N$\mathsf{^{3+}}$, O$\mathsf{^{3+}}$, O$\mathsf{^{4+}}$, F$\mathsf{^{3+}}$, F$\mathsf{^{4+}}$ and Ne$\mathsf{^{4+}}$

State-resolved valence shell photoionization of Be-like ions: experiment and theory

“…Resolving powers E/∆E of more than 20,000 were reached. The scan data were normalized to absolute measurements available from previous work [16,29]. The total systematic uncertainty of the cross sections thus determined is about ±20 %.…”

“…The bottom panel presents the measured data as points joined by a solid line. The measured relative cross section function was normalized to the absolute data of Bizau et al [29]. Figure 13 provides a comparison of the 40-meV resolution experimental overview of photoionization of N 3+ ions with a model spectrum obtained from the present Breit- Table 1.…”

“…Figure 14 shows a threshold scan for photoionization of N 3+ ions. The relative scan cross sections are normalized to the absolute measurements of Bizau et al [29]. The simplest cross section model to represent the photoionization threshold is a step Cross section ( Mb ) function with three steps, each associated with one of the three 3 P o J metastable initial states.…”

“…The theoretical features can be recognized in the experimental data displayed in the bottom panel of the figure. These data are from the measurements by Bizau et al [29] carried out at the Aarhus photon-ion merged beams facility [28] Cross section ( Mb ) To elucidate the strengths of the individual O 4+ photoionization contributions from the many resonances calculated within the present Breit-Pauli R-matrix approach for the initial 1 S and 3 P o states, figure 19 shows the theoretical data from the first 4 panels of figure 18, this time convoluted with a 50 meV FWHM gaussian. As in the previous examples, the convolution greatly simplifies the photoionization spectra and clearly demonstrates where the dominant resonance strengths are located.…”

“…The techniques and applications of merged beams have been reviewed by West [27] and more recently by Kjeldsen [28]. The berylliumlike sequence was addressed previously in a number of merged beams experiments providing absolute cross sections up to the (2pnl) resonance-series limits for photoionization of B + ions with an energy resolution of 25 meV at around 30 eV photon energy [15], for photoionization of C 2+ with an energy resolution of 30 meV at around 50 eV photon energy [16], for photoionization of N 3+ with a quoted energy resolution of 230 meV at around 70 eV photon energy [29], and for photoionization of O 4+ with an underestimated energy resolution of 250 meV at around 110 eV photon energy [29,30]. For selected resonances in the photoionization of C 2+ ions measurements with energy spreads as low as 7.5 meV have been reported [17].…”