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

Excitation energies of $ns$, $np$, $nd$, and $nf$ ($n \leq$ 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 $(F = 2\ M =0) \leftrightarrow (F = 1\ M =0)$ ground-state hyperfine transition is found to be -0.0582 Hz/(kV/cm)$^2$, in slight disagreement with the experimental value -0.061$\pm$0.002 Hz/(kV/cm)$^2$. Matrix elements used in evaluating polarizabilities, hyperfine constants, and the quadratic Stark shift are obtained using all-order method.