ORIGIN OF ANOMALIES IN PHOTOEMISSION FROM THE CONDUCTION-BAND OF POTASSIUM

Above the threshold for K 3p excitation, the conduction band photoemis sion spectrum of metallic potassium is dominated by core excitation co upled to autoionization. This accounts for the observation of a strong response in regions where k-conserving transitions are forbidden, as well as for the angle-integrated character of data taken in an angle-r esolved mode. The anomalous triangular peak at the Fermi level observe d with photon energies near 25 eV is due to the selective enhancement of the 4p character of the conduction band by autoionization involving electrons excited into the normally empty 3d bands.