Behaviours of the excited states 1s2np along lithium isoelectronic sequence from Z = 11 to 20

Based on the obtained energy values of 1s2np (n ≤ 9) states for lithium-like systems from Z = 11 to 20 (by the authors of this paper: Hu M H and Wang Z W 2004 Chin. Phys. 13 662), this paper determines the quantum defects, as slowly varying function of energy, of this Rydberg series. Using them as input, it can predict the energies of any highly excited states below the ionization threshold for this series according to the quantum defect theory. The regularities of variation for quantum defects of the series along this isoelectronic sequence are physically analysed and discussed. The screening parameters, which are equal to the effective screening charge of the core-electrons, are also obtained