Symmetrical fluorescence yield profiles and asymmetrical electron yield profiles of the preresonances at the La $N_{IV,V}$ x-ray absorption edge are experimentally observed in ${\mathrm{LaPO}}_4$ nanoparticles. Theoretical studies show that they are caused by interference effects. The spin-orbit interaction and the giant resonance produce symmetry entangled intermediate states that activate coherent scattering and alter the spectral distribution of the oscillator strength. The scattering amplitudes of the electron and fluorescence decays are further modified by the spin-orbit coupling in the final $5p^5\epsilon l$ and $5p^{5}4f^1$ states.

• Received 3 July 2009

DOI:https://doi.org/10.1103/PhysRevLett.103.137401