Relativistic many - body calculation of energies , lifetimes , hyperfine constants , and polarizabilities in 7

The excitation energies of ns, np, nd, and nf n 6 states in neutral lithium are evaluated within the framework of relativistic many-body theory. First-, second-, third-, and all-order Coulomb energies and firstand second-order Breit corrections to energies are calculated. All-order calculations of reduced matrix elements, oscillator strengths, transition rates, and lifetimes are given for levels up to n=4. Electric-dipole 2s −np , electric-quadrupole 2s−nd , and electric-octupole 2s−nf , matrix elements are evaluated to obtain the corresponding ground-state multipole polarizabilities using the sum-over-states approach. Scalar and tensor polarizabilities for the 2p1/2 and 2p3/2 states are also calculated. Magnetic-dipole hyperfine constants A are determined for low-lying levels up to n=4. The quadratic Stark shift for the F=2 M =0 ↔ F=1 M =0 ground-state hyperfine transition is found to be −0.0582 Hz / kV /cm 2, in slight disagreement with the experimental value −0.061 0.002 Hz / kV /cm 2. Matrix elements used in evaluating polarizabilities, hyperfine constants, and the quadratic Stark shift are obtained using the all-order method.