Laser photo-ionization efficiency of ¹¹¹Ag for medical use in the SPES-ISOLPHARM project

The ISOLPHARM project has the goal of producing innovative radiopharmaceuticals taking advantage of the radionuclides produced in the SPES ISOL facility, nearing completion at INFN-LNL. One of the main radionuclides of interest for the project is ¹¹¹Ag, which is a novel candidate for therapeutic and theranostic applications in nuclear medicine. Among the various steps of the ISOL technique, which stands for "Isotope Separation On-Line", the main stages contributing to selectivity are ionization and mass separation. In general, the latter ensures isotopic selectivity, while the former can be element-specific. In particular, the Laser Ion Source (LIS) is the one that guarantees the best selectivity, as it can provide to each element the precise energy required for ionization. Moreover, if narrowband lasers are available, the isotopic shift in one of the ionization steps can be used to tell apart different isotopes as well. The aim of this study is to assess, through the formalism of the reduced density matrix, the optimum laser power to maximize the ion yield and the isotopic selectivity of ¹¹¹Ag in the SPES online environment. Furthermore, other aspects affecting the yield, such as time delay, power broadening and Doppler broadening, are evaluated.