Relativistic multireference coupled-cluster theory based on a B-spline basis: Application to atomic francium

摘要

In this paper, we report the relativistic Fock space multireference coupled-cluster method for atomic structure calculations. We use the no-pair Dirac-Coulomb-Breit Hamiltonian, together with a finite B-spline basis set to expand the large and small components of the Dirac wave function. Our method is applied to calculate ionization energies, reduced matrix elements, lifetimes, and polarizabilities for many states of atomic francium. To evaluate uncertainties of our results and investigate the role of electron correlation effects, we carry out calculations using approximated models at different levels. The quality of our calculations is assessed by comparing with available experimental results, showing a good agreement. In addition, the tune-out wavelengths of the ground state in the range of 340-800 nm, the magic wavelengths for the transition 7s-8s in the range of 800-1500 nm and the transition 7s-7p in the range of 600-1500 nm are determined by evaluating the dynamic polarizabilities of the 7s, 8s, and 7p states for a linearly polarized light. These tune-out and magic wavelengths may be useful for laser cooling and trapping of the Fr atom, and for related high-precision trapping measurements.