Paramagnon satellites in photoemission spectra of chemisorbed hydrogen

A model for the chemisorption of hydrogen on transition metals is considered taking the intrametallic exchange forcesI and the extra-atomic exchangeJ into account. The extra-atomic exchange couples the single particle states of the adatom to the particle-hole states of the metal. This leads to dynamic effects similar to those found in soft X-ray spectra of metals and in the image force dynamics of chemisorbed atoms. Such dynamic effects can be expected to be particularly large near a ferromagnetic instability of the metal. The theoretical treatment of these effects is complicated because of Kondo type divergencies. ForJ large compared to the band widthB a simplified treatment is adopted avoiding explicit consideration of the Kondo effect. The intermetallic exchange effects then can be incorporated into the calculation of the dynamic effects. A simplified and crude estimate of the exchange enhancement of the dynamic effects near a ferromagnetic instability indicates strong paramagnon satellites in the photoemission spectrum leading to a broadening of the unperturbed spectrum.