Photoelectron Spectroscopic Measurements of Core Level Binding Energies of Yttrium, Lanthanum and Cerium

X-ray photoelectron spectra have been measured on in situ evaporated films of yttrium, lanthanum, and cerium by the use of an electron energy analyser of the parallel plate electrode type. The binding energies of electronic core levels have been determined. Results are compared with the values cited in typical X-ray atomic energy tables. The binding energies of the M 4 (3 d 3/2 ) and M 5 (3 d 5/2 ) levels of lanthanum and cerium as well as the N 2 (4 p 1/2 ) and N 3 (4 p 3/2 ) levels of lanthanum are all found to be split into two components. Possible origins of the splitting are discussed, although no definite conclusion is drawn out.