Theoretical Research On The Structure And Spectral Property Of The Excited States For Lithium-like Systems From Z=11 To 20

Recently, the full core plus correlation (FCPC) method, has been developed to calculate the ionization potentials, excitation energy, fine structure and other property of ground states and low states for the lithium-like systems with a 1s2-core. Most of the calculated excitation energies and fine-structure splittings are in agreement with experimental data up to not more than 1 cm-1. Not long ago, this method was applied to research the radial electron density, the hyperfine structure and the gj-fators for the lithium-like systems. Most of the results are satisfied. As a new form of CI method, the FCPC method not only effectively considers the correlation effect of electrons, relativistic effect, mass polarization effect and quantum-electrodynamics effect, but also overcomes the difficulty of the slow convergence rate which appears in the course of dealing with atomic systems with a 1s2-core by using the traditional CI method. In this way, it has become a very effective theoretical method to study the structure and property of lithium-like systems with a 1s2-core.On the basis of the successful calculations of the structure and property of lithium-like systems with the characteristic FCPC method, we will extend it to lithium-like systems with higher nuclear charge and extrapolated to higher energy region. Combined with the single channel quantum defect theory, we realize the theoretical research on the structure and spectral property of the excited states for highly ionized lithium-like systems from Z=11 to 20, we obtained the following conclusions:Firstly, we calculated the ionization potentials and excitation energies of 1s2nl states (l=s, p, d, f; 6 ≤ n ( 9) for lithium-like ions from Na IX to Ca XVIII, the relativistic effects () and mass polarization effect are evaluated with the Pauli-Breit operators as the first-order perturbation corrections. In order to obtain the high-precision theoretical results, the contribution from quantum-electrodynamics (QED) correction is also included by using the effective nuclear charge. The fine structures of 1s2nl states (l=p, d, f; 6 ≤ n ( 9) for lithium-like ions are determined by computing the expectation values of the spin-orbit and spin-other-orbit interaction operators in the LSJ coupling scheme. Compared our results and experimental data in the literature, we find that the agreement of our results with available experimental data is satisfactory for these states. The results of 1s2nl states (l ≠ 0) for lithium-like ions from Na IX to Ca XVIII obtained in this work show a well behaved isoelectronic regularity of fine-structure splitting, namely, the fine structure caused mainly by the spin-orbit and spin-other-orbit interactions in atomic system increases with the increase of the nuclear charge. It is reasonable to question the reliability of fine structure of 1s26d state for NaIX in experimental data, which obviously deviates from the result obtained in this work.Based on the energies and wavefunations of 1s2nl excited states (l=s, p, d, f; 6 ≤ n ( 9) for lithium-like ions obtained from the FCPC method, the quantum defects for every Ryderg series of these ions are determined with the single channel quantum defect theory, which should be a smooth function of energy and approximated by a weakly varying function of energy. With the quantum defects obtained in this work as input, the term energies for lowly excited states (n ≥ 10) are calculated again by the iteration method and the relative deviation η% is within 0.0035. Thus, the accurate predictions make it possible to predict the highly excited energy below the threshold region of these systems and the results should be reasonable and accurate. The results in this work enrich the basic data greatly, and provide the useful reference for the study in spectral and other regions.The dipole oscillator strength is the most important spectral property of atomic system. Theoretically, the agreement among the results of the three expressions becomes an indication of the accuracy of the wave fun...