X-RAY RESONANCE SCATTERING IN UAs.

Resonant enhancement of the magnetic x-ray scattering cross- section in UAs has been investigated by tuning the incident x-ray energy through the Uranium M sub (III), and M sub (IV), and M sub (V) absorption edges. At the M sub (IV) edge the intensity for the (0,0,5/2) magnetic reflection is enhanced by 10 sup 7 and is a remarkable 1% of the intensity at the (0,0,2) charge peak. At the M sub V and M sub (III) edge the enhancements are 10 sup 5 and 50, respectively. The dramatic enhancement at M edges has been predicted by Hannon, et al. , and arises from strong electric multipole transitions between atomic core states and the exchange-split Fermi edge states. The polarization dependence of the magnetic scattering through the M sub (IV) resonance agrees with the selection rules for such transitions.