Model potential study of Rydberg one-electron spectrum of thallium

Semi-empirical model potential calculations of excitation energies, fine structure splittings, oscillator strengths and line strengths ratios were computed for high Rydberg transitions in principal, sharp and diffuse series of thallium one-electron spectrum with allowance for core-valence electron correlations in core polarization picture. Relativistic effects are fully included through solving Dirac equations and core-valence electron correlation is represented in core polarization picture by appropriate term in model potential optimized to reproduce ionization energies of the system for lowest states of given lull) symmetry. The dipole-moment operator of transition is modified in accordance. Systematic trends are investigated in line strength ratios and oscillator strengths along the spectral series, the latter showing hydrogen-like behavior for large n* effective quantum number of upper states of transition. The influence of core-valence correlation (core polarization) on line strength ratios and oscillator strengths along the spectral series is studied in detail demonstrating its importance even for transitions to highly excited Rydberg states with n = 20. The strong effect of cancellation of positive and negative contributions to transition matrix element was observed for oscillator strengths and line strength ratios in principal series of thallium spectrum. (C) 2020 Elsevier Inc. All rights reserved.