Isotope shiftstudies in Zr I by Doppler-free saturated absorptionspectroscopy and pseudo-relativistic Hartree-Fock calculations:I. Transitions 4d35s-4d25s5p

Abstract

The isotope shifts of twelve Zr I 4d35s-4d25s5ptransitions in the green and the 4d35s a 5F5-4d35py 5G6 `reference' transitionat 468.78 nm have been determined by the technique of Doppler-free saturated absorption spectroscopy in a sputteredvapour. The specific mass shift (SMS) and the field shift (FS)contributions were separated using a King-plot analysis, inwhich the SMS of the 468.78 nm referencetransition was estimated from ab initio calculations.The 4d35s-4d25s5p transitions, which involve anelectron jump 4d→5p, represent an importantclass in which the SMS is large compared with the FS. This enables SMSs to bedetermined to high accuracy (1-2%), thus affording stringenttests of ab initio calculations. An interpretation ofthe isotope shifts was performed using refined multiconfigurational fine-structure calculations andpseudo-relativistic Hartree-Fock (PSUHFR) calculations. TheSMS values deduced from the PSUHFR calculationsare found to be systematically higher than the experimentalSMS values for all levels, by an average factor of 1.45±0.07 (where the uncertainty represents the standarddeviation of the distribution). Using PSUHFR estimates for theelectron density at the nucleus together with the experimentalFS for the 4d35s a 5F5-4d25s5p y 5G6 transition,the 90Zr-92Zr FSs for some relevantodd-parity configurations are predicted to be FS(4d35p)=-419 MHz, FS(4d25s6p) = + 281 MHz and FS(4d5s25p) = + 1012 MHz, relative to the lower-levelconfiguration 4d35s.