SPIN-RESOLVED AND HIGH-ENERGY-RESOLUTION XPS STUDIES OF THE 3S AND 2SLEVELS OF METALLIC COBALT

Spin-resolved and high-energy-resolution x-ray photoelectron spectrosc opy (XPS) measurements of the 3s and 2s levels of metallic cobalt are reported. The high-resolution 3s spectrum shows a multiplet splitting Delta E(3s) of 3.3 +/- 0.3 eV. The metallic value and literature Delta E(3s) values for CoF2 and CoF3 display a linear variation with (2S+1) in accord with the Van Vleck model. This finding, combined with the a bsence of core-level XPS satellites in Co metal attributable to locali zed final-state 3d charge fluctuations, implies that intra-atomic exch ange dominates the Co 3s spectrum, and indicates that the creation of a core hole does not alter the 3d electron population in metallic Co, CoF2, or CoF3. The large role played by intra-atomic exchange is expli citly revealed by spin-resolved XPS (SRXPS) investigation of the Co 3s level. The SRXPS data show a predominantly minority-spin character fo r the main (low-binding-energy) 3s component, and a strong majority-sp in character for the smaller 3s component at higher binding energy. Al though high resolution Co 2s XPS measurements give no indication of mu ltiplet structure, SRXPS Co 2s measurements reveal a 0.65 +/- 0.3 eV e xchange splitting between majority-spin and minority-spin components, as well as a significant spin dependence to the L(1)L(2,3)M(4,5) Coste r-Kronig transition probability.