<i>K</i>-shell photoabsorption of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">N</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>molecule

The K-shell photoabsorption spectrum of the ${\mathrm{N}}_{2}$ molecule, recorded with unprecedented energy resolution and statistical accuracy, reveals several new Rydberg transitions and double-excitation states. The nearly identical term values, vibrational frequencies and internuclear separations of the 1s-excited states of ${\mathrm{N}}_{2}$ and of the 2\ensuremath{\pi}-excited states of NO, allow for a complete peak assignment for the ${\mathrm{N}}_{2}$ Rydberg series and strongly support both the core-hole localization picture and equivalent-core model. Subtle differences are related to the final-state charge distribution in the vicinity of the nuclei and to the bonding character of the valence orbitals.