Single-photon photoionization of oxygen-like Ne III

Abstract

We offer a theoretical and experimental study of the single-photon photoionization of Ne III. The high photon flux and the high-resolution capabilities of the Advanced Light Source at the LBNL were employed to measure absolute photoionization cross sections. The resulting spectrum has been benchmarked against high accuracy relativistic Breit-Pauli $R$-matrix calculations. A large close-coupling wave function expansion which comprises up to 58 fine-structure levels of the residual ion Ne IV of configurations $2s^{2}2p^3$, $2s2p^4$, $2p^5$, $2s^{2}2p^{2}3s$, $2s^{2}2p^{2}3p$ and $2s^{2}2p^{2}3d$ was included. A complete identification of the measured features was achieved by considering seven low-lying levels of Ne III. We found that the photoionization cross-section (${\sigma }_{PI}$) exhibits the presence of prominent resonances in the low-energy region near the ionization thresholds that correspond to low-lying levels. These include high-peak narrow resonances with almost zero background introduced by relativistic effects. However, there does not exist a significant contribution to ${\sigma }_{PI}$ from relativistic effects at the high-energy interval of the present study.

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