Probing the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mn>4</mml:mn><mml:mi>p</mml:mi></mml:math>electron-spin polarization in NiO

K-edge resonant x-ray magnetic scattering experiments have been performed on antiferromagnetic NiO. The observation of two resonances at the K edge allows the construction of models to compare the electronic properties of NiO and the observed resonant magnetic x-ray scattering. From the polarization analysis of the scattered beam, a quadrupolar transition $(1s\ensuremath{-}3d)$ and a dipolar transition $(1s\ensuremath{-}4p)$ are identified. While the quadrupolar transition can be modeled using an atomic picture for the $3d$ electrons, the dipolar transition is associated to a broadband structure of p electrons and its energy profile is compared to electronic band-structure calculations.