New Observations in the K-shell Photoabsorption of the N sub 2 Molecule.

The K-shell photoabsorption spectrum of the N sub 2 molecule, recorded with unprecendented 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 N sub 2 and of the 2pi-excited states of NO, allows for a complete peak assignment for the N sub 2 Rydberg series and strongly supports both 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.