Laser isotope separation (review)

Part I of the review (Sees. 1–5) classifies the optical (photochemical and photophysical) isotope separation methods, gives the history of their development, and demonstrates the advantages of laser radiation. The problem of isotopically selective excitation and isotopic shifts in the spectra of atoms and molecules, and also limitations of the selectivity and methods for increasing it are considered in Sec. 2. The method of selective multistep photoionization of atoms, general relationships applying to this method, principal experiments (on Rb, U, etc.), methods for increasing the photoionization cross section of excited atoms, and limitations on ionization selectivity are discussed in Sec. 3. The method of selective two-step photodissociation of molecules and limitations (bottleneck effect due to the rotational structure, steepness of the photoabsorption edge, and nonselective thermal excitation), and the first experiments (on NH₃, BCl₃) are analyzed in Sec. 4. The method of selective photopredissociation of molecules, its limitations and advantages, first experiments (on H₂CO and I₂), and its potential applications in isotope separation are discussed in Sec. 5 (Sees. 1, 3, and 4 are by V. S. Letokhov and Sees. 2 and 5 are by C. B. Moore).