Isotope shift studies in ZrI by Doppler-free saturated absorption spectroscopy and pseudo-relativistic Hartree-Fock calculations: I. Transitions 4d(3)5s-4d(2)5s5p

摘要

The isotope shifts of twelve Zr I 4d(3)5s-4d(2)5s5p transitions in the green and the 4d(3)5s a(5)F5-4d(3)5p y(5)G(6) 'reference' transition at 468.78 nm have been determined by the technique of Doppler-free saturated absorption spectroscopy in a sputtered vapour. The specific mass shift (SMS) and the field shift (FS) contributions were separated using a King-plot analysis, in which the SMS of the 468.78 nm reference transition was estimated from ab initio calculations. The 4d(3)5s-4d(2)5s5p transitions, which involve an electron jump 4d --> 5p, represent an important class in which the SMS is large compared with the FS. This enables SMSs to be determined to high accuracy (1-2%), thus affording stringent tests of ab initio calculations. An interpretation of the isotope shifts was performed using refined multiconfigurational fine-structure calculations and pseudo-relativistic Hartree-Fock (PSUHFR) calculations. The SMS values deduced from the PSUHFR calculations are found to be systematically higher than the experimental SMS values for all levels, by an average factor of 1.45 +/- 0.07 (where the uncertainty represents the standard deviation of the distribution). Using PSUHFR estimates for the electron density at the nucleus together with the experimental FS for the 4d(3)5s a(5)F(5)-4d(2)5s5p y(5)G(6) transition, the Zr-90-Zr-92 FSs for some relevant odd-parity configurations are predicted to be FS(4d(3)5p) = -419 MHz, FS(4d(2)5s6p) = +281 MHz and FS(4d5s(2)5p) = +1012 MHz, relative to the lower-level configuration 4d(3)5s. [References: 47]