Theoretical study of lifetimes and polarizabilities in Ba+
Abstract
The 6s-npj (n=6-9) electric-dipole matrix elements and 6s-ndj (n=5-7) electric-quadrupole matrix elements in Ba+ are calculated using the relativistic all-order method. The resulting values are used to evaluate ground state dipole and quadrupole polarizabilities. In addition, the electric-dipole 6pj-5dj' matrix elements and magnetic-dipole 5d5/2-5d3/2 matrix element are calculated using the same method in order to determine the lifetimes of the 6p1/2, 6p3/2, 5d3/2, and 5d5/2 levels. The accuracy of the 6s-5dj matrix elements is investigated in detail in order to estimate the uncertainties in the quadrupole polarizability and 5dj lifetime values. The lifetimes of the 5d states in Ba+ are extremely long making precise experiments very difficult. Our final results for dipole and quadrupole ground state polarizabilities are alphaE1 = 124.15 a30 and alphaE2 = 4182(34) a50, respectively. The resulting lifetime values are tau(6p1/2)=7.83 ns, tau(6p3/2)=6.27 ns, tau(5d3/2)=81.5(1.2) s, and tau(5d5/2)=30.3(4) s. The extensive comparison with other theoretical and experimental values is carried out for both lifetimes and polarizabilities.