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

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 first- and 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 2p_1/2 and 2p_3/2 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.