Experimental and theoretical near-edge x-ray-absorption fine-structure studies of NO+

Abstract

Experimental near-edge x-ray-absorption fine-structure (NEXAFS) spectra of the nitrosonium ${\mathrm{NO}}^{+}$ ion are presented and theoretically analyzed. While neutral NO has an open shell, the cation is a closed-shell species, which for NEXAFS leads to the simplicity of a closed-shell spectrum. Compared to neutral NO, the electrons in the cation experience a stronger Coulomb potential, which introduces a shift of the ionization potential towards higher energies, a depletion of intensity in a large interval above the ${\ensuremath{\pi}}^{*}$ resonance, and a shift of the ${\ensuremath{\sigma}}^{*}$ resonance from the continuum to below the ionization threshold. NEXAFS features at the nitrogen and oxygen $K$ edges of ${\mathrm{NO}}^{+}$ are compared, as well as NEXAFS features at the nitrogen edges of the isoelectronic closed-shell species ${\mathrm{NO}}^{+}, {\mathrm{N}}_{2}$, and ${\mathrm{N}}_{2}{\mathrm{H}}^{+}$.