Abstract
Configuration–interaction perturbation theory (CI–PT) is applied to calculations of low-energy states of Pu II. This ion is quite challenging due to a large number of possible determinants arising from seven valence electrons and strong relativistic effects. The CI–PT calculations agree with experiments for the energies and g-factors for many low-energy states that allowed positive identification of the theoretical levels. Isotope shifts were also used to aid in identification, and, in case of the odd states, fitting with three independent parameters was used to match theoretical isotope shifts to the experimental values with good accuracy. The CI–PT approach tested here on the Pu II ion can be generally used to calculate properties of many complex atoms, including U I that can find application in fundamental and applied science.
Highlights
Plutonium is an important actinide element, used in many applications such as nuclear weapons and nuclear energy
One important thing to note is that the website of Laboratoire Aime-Cotton where actinide energies, g-factors, parametric state assignment, and isotope-shifts could be found
The method of Configuration–interaction perturbation theory (CI–PT) is quite promising for calculations of properties of low-energy states of multi-valence atoms, such as the 7-valence electron Pu II considered here
Summary
Plutonium is an important actinide element, used in many applications such as nuclear weapons and nuclear energy. Used in Pu characterization applications, laser-induced breakdown spectroscopy (LIBS) needs theoretical input, especially transition probabilities, lifetimes, and state population distributions, since the excitations of many levels in this method lead to complex spectra with a large number of lines merged Many theories, such as relativistic many-body perturbation theory (MBPT), or a combination of configuration interaction with MBPT (CI-MBPT) were not applied to Pu and many similar atoms and ions, while such theories are quite promising. In the case of CI-MBPT, while this theory includes most important relativistic effects [the Dirac Hartree–Fock (DHF) basis set] and valence–core interactions (in the second-order of MBPT), it has an additional problem in atoms with more than two valence electrons that it is difficult to saturate valence–valence interactions Some solution to this problem was the introduction of scaling parameters, so that agreement with experiments for energies was substantially improved, for example in case of U III and Th I, allowing matching theoretical and experimental levels [7,8]. These configuration energies were used in our calculations to adjust configuration expansions to achieve correct results in the first approximation
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