Perturbations and Coupling in the d^9sp Configurations of Cu i, Zn ii, Ag i, Cd ii, and Tl iii

Application of intermediate coupling theory to 3d⁹4s4p in Cu i and Zn ii revealed strong perturbations that could not be due to configuration types 3d¹⁰nl. The 3d⁹4s4p levels except 4s4p(¹P°)3d^{9 2}P° were then fitted by including interaction with 3d⁸4s²4p. Energy parameters for 3d⁸4s²4p, for which no experimental levels are known, were fixed at values based on related spectra. The results show that this interaction accounts for the major distortions of 3d⁹4s4p in Cu i and Zn ii. The resulting interaction-parameter values appear consistent with values for related iron-group spectra. The discrepancies between calculated and experimental positions for $({¹P}^0)3d^9{{²P}^0}_{\frac{1}{2},\frac{1}{2}}$ are consistent with known 3d¹⁰np²P⁰ series perturbations in Cu i, Zn ii. Calculations without interaction for 4d⁹5s5p in Ag i and Cd ii indicate interaction with 4d⁸5s²5p, but weaker than the corresponding interaction in the Cu i sequence. The levels of Tl iii (5d⁹6s6p+5d¹⁰7p) were fitted with configuration interaction. One experimental d⁹sp level is rejected in Zn ii, Ag i, and Tl iii. Corresponding new levels are found for Zn ii and Ag i. Leading eigenvector components for the d⁹sp levels in the [sp(S_IL_I), d⁹]SL and [sp(S_IL_I)J_I, (d⁹)J_II]J coupling schemes are given for all five spectra. The Tl iii levels are assigned J_IJ_II names as most appropriate.