Comparison of Theoretical and Experimental Level Values of the<i>n</i>= 2 Complex in Ions Isoelectronic with Li, Be, O and F

Abstract

The differences between observed and theoretical values of level intervals within the n = 2 complex in ions isoelectronic with Li, Be, 0 and F have been studied as functions of Z.The theoretical values are based on the tables of Cheng, Kim and Desclaux.For spin-orbit intervals, u(theor) is taken as their multiconfiguration Dirac-Fock value with Breit correction (MCDF + B), for other intervals within the same configuration the Z-independent correlation energy from Cheng, Froese Fischer and Kim is added, and for interconfiguration intervals a Lamb-shift correction is also included, obtained by transforming the values of Cheng et al. into a smooth function of Z.The difference U (obs) -U (theor) is then expressed by the formula A + B ( Z -C)-' t a(Z -s)", where the first two terms account for the residual correlation energy and the last term comprises all additional relativistic and radiative corrections.In a few cases we had t o use two such terms with opposite sign and exponents differing by 2 to 3 units.The constants A , B, C, a and x are adjusted to fit the observations within their error limits.As compared to a fitted polynomial, the present formula is much better suited for extrapolation and provides a sharper test of the experimental data, especially at the high2 end of a sequence.It has revealed a number of incorrect line identifications in the Be sequence.The results of the analyses are summarized in tables of recommended level values and wavelengths, extending to Z = 36 and in some cases to Z = 4 2 .The wavelengths obtained for the resonance lines in the Be, 0 and F sequences may become useful as wavelength standards.shown in Table IV.We have chosen the component 2P,,2-2S,,2 for which relativistic effects are largely cancelled because of