SINGLE AND DOUBLE. PHOTOIONIZATION OF LANTHANIDE ELEMENTS IN THE REGION OF THE 5p EXCITATION C. DZIONK, W. FIEDLER, C. KORTENKAMP, M. v. LUCKE and P. ZIMMERMANN J. Phys. Colloques, 48 C9 (1987) C9-501-C9-504 DOI: 10.1051/jphyscol:1987981