{\it K}-Shell Photoionization of Be-like and Li-like Ions of Atomic Nitrogen: Experiment and Theory

TL;DR

This study measures and compares the absolute cross sections of K-shell photoionization in Be-like and Li-like nitrogen ions using high-resolution experiments and theoretical models, enhancing understanding of atomic nitrogen spectra.

Contribution

It provides new high-resolution experimental data and compares it with advanced theoretical calculations for K-shell photoionization of nitrogen ions, improving spectral characterization.

Findings

Good agreement between experiment and theory for resonance features.

Identification of 1s → 2p and 1s → 3p resonances.

Enhanced understanding of nitrogen ion spectra.

Abstract

Absolute cross sections for the {\it K}-shell photoionization of Be-like and Li-like atomic nitrogen ions were measured by employing the ion-photon merged-beam technique at the SOLEIL synchrotron radiation facility in Saint-Aubin, France. High-resolution spectroscopy at nominal resolutions of 38 meV, 56 meV, 111 meV, 133 meV FWHM for Be-like and 125 meV FWHM for Li-like atomic nitrogen ions was achieved for the photon energies ranging from 410 eV up to 460 eV. The experimental measurements are compared with theoretical estimates from the multi-configuration Dirac-Fock (MCDF), R-matrix and an empirical method. The interplay between experiment and theory enabled the identification and characterisation of the strong 1s $\rightarrow$ 2p resonances features observed in the {\it K}-shell spectra of each ion and the region around 460 eV for the 1s $\rightarrow$ 3p resonance of the N$^{3+}$ ion yielding suitable agreement with experiment.