Theoretical study of lifetimes and polarizabilities in Ba+

The 6s-np(j) (n=6-9) electric-dipole matrix elements and 6s-nd(j) (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 6p(j)-5d(j)(') matrix elements and magnetic-dipole 5d(5/2)-5d(3/2) matrix element are calculated using the same method in order to determine the lifetimes of the 6p(1/2), 6p(3/2), 5d(3/2), and 5d(5/2) levels. The accuracy of the 6s-5d(j) matrix elements is investigated in detail in order to estimate the uncertainties in the quadrupole polarizability and 5d(j) 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 alpha(E1)=124.15a(0)(3) and alpha(E2)=4182(34)a(0)(5), 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. An extensive comparison with other theoretical and experimental values is carried out for both lifetimes and polarizabilities.