Surface Ionization. III. The First Ionization Potentials of the Lanthanides

The surface ionization comparison technique was used to measure the first ionization potentials of the lanthanide elements. Values obtained were La, 5.55 ± 0.05 eV; Ce, 5.54 ± 0.06; Pr, 5.40 ± 0.05; Nd, 5.49 ± 0.05; Sm, 5.61 ± 0.05; Eu, 5.64 ± 0.05; Gd, 6.16 ± 0.05; Tb, 5.89 ± 0.04; Dy, 5.82 ± 0.03; Ho, 5.89 ± 0.03; Er, 5.95 ± 0.03; Tm, 6.03 ± 0.04; Yb, 6.04 ± 0.04; and Lu, 5.32 ± 0.05. The IP of Pm is estimated to be 5.55 eV. The reference element used was silver. A tabulation of all known reported values is included, and comparisons are made. Agreement is generally good.