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Techniques of stepwise laser excitation and photoionization have been applied to study spectroscopic properties of neutral atoms of lanthanides and actinides. The spectroscopic properties that can be determined include: ionization potential, energy levels, isotope shifts, hyperfine structure, lifetimes of energy levels, branching ratios and oscillator strengths. We discuss the laser methods used to obtain these properties (with emphasis on ionization potentials) and give examples of results obtained for each. The ionization potentials obtained by laser technique are in eV: Ce, 5.5387(4); Pr, 5.464(12); Nd, 5.5250(6); Sm, 5.6437(6); Eu, 5.6704(3); Gd, 6.1502(6); Tb, 5.8639(6); Dy, 5.9390(6); Ho, 6.0216(6); Er, 6.1077(10); U, 6.1941(5) and Np, 6.2657(6). Regularities in the f/sup N/s/sup 2/ - f/sup N/s ionization limits for the lanthanides have been found as a result of these accurate values and previously known accurate values for the others. Multistep photoionization has been employed for laser isotope separation and for studies of autoionization. 75 references, 16 figures, 7 tables. |
