Towards molecular laser separation of uranium isotopes

About half a century ago, active research began on the use of lasers for the separation of isotopes, including uranium isotopes. In a number of highly developed countries, projects on laser separation of uranium isotopes were initiated. However, in the late 1990s, these projects were closed. At the same time, research on laser separation of uranium isotopes is being carried out in a number of countries at the present time. Research today is mainly focused on the development of low energy methods. A review of the results of studies on molecular laser isotope separation (MLIS) of uranium is presented. MLIS methods, including low-energy methods, as well as the physicochemical processes underlying them, are considered. The infrared and ultraviolet absorption spectra of $\rm UF_6$ molecules, which form the basis of uranium MLIS methods, are presented and discussed. Lasers that have been developed and used to excite and dissociate $\rm UF_6$ molecules are briefly described. The results of studies on laser dissociation of $\rm UF_6$ molecules using different excitation schemes and laser separation of uranium isotopes are presented and analyzed. Applications of low-energy MLIS methods, including SILEX technology, for the separation of uranium isotopes are considered. In the context of molecular laser separation of uranium isotopes using low-energy methods, the recently obtained results on the separation of isotopes in $\rm SF_6$ and $\rm CF_3Br$ molecules, which are close analogs of $\rm UF_6$ molecules in a number of spectroscopic properties, are presented and analyzed. Approaches that can be a promising alternative to low-energy MLIS methods are discussed. Data on the efficiency of some laser methods and their comparison with each other are given. A brief historical excursion into research on laser separation of uranium isotopes is given.