Construction of RKR-QDT atomic model potentials for the calculation of Lithium polarizabilities and hyper-polarizabilities

Abstract

Atomic local model potentials, reproducing experimental energy levels, are built by a combination of the Rydberg–Klein–Rees (RKR) inversion method with the quantum defect theory (QDT). An efficient iterative procedure leads to the production of spectrum-equivalent potentials containing a number of free parameters. These parameters can be adjusted in order to improve the accuracy of other physical properties, calculated via the constructed potentials. The high efficiency of the method is demonstrated by calculating the lifetimes of singly excited states as well as the dipole and quadrupole polarizability and hyper-polarizability of the ground 1s22s and first excited 1s22p state of Lithium. The obtained value γ = 3390 au for the ground state hyper-polarizability is in excellent agreement with other elaborate theoretical calculations. The scalar hyper-polarizability of 1s22p acquires a much higher value, γ0 = 1.002 × 107 au, while its tensor part is γ2 = −0.621 × 107 au.