Isotope shifts and electron densities in W I. II. Theoretical field shifts and configuration mixing

Abstract

The isotope shift in the arc spectrum of tungsten was studied in seven lines by means of a photoelectric recording Fabry-Perot spectrometer with digital data processing for the isotopes 182W, 183W, 184W and 186W using highly enriched isotope samples. The observed shifts were separated into mass shift and field shift by means of a King plot with optical reference data. The measured field shifts show that the odd levels z 7Po2,3,4 are composed of the configurations 5d56p, 5d46s6p and 5d36s26p. Non-relativistic Hartree-Fock calculations of the field shifts between pure configurations allow a determination (or a reliable estimate) of the mixing coefficients of these levels. The relative field shifts are: (182, 183) 0.607 (5); (182, 184) 1.154 (4); (184, 186) 1. Then the nuclear parameters λAA' (≃ the changes in mean-square nuclear charge radii) are equal to (182, 183) 0.051 (5), (182, 184) 0.097 (8) and (184, 186) 0.084 (7) fm2.