Eur. Phys. J. D 11, 197-205 (2000)
https://doi.org/10.1007/s100530070084

Finestructure, hyperfine structure and isotope shift of 4f¹²6s7s in Er I

¹ Max Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Rudower Chaussee 6, 12489 Berlin, Germany
² Institut für Atomare und Analytische Physik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany
³ Optisches Institut, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany

Received: 16 May 1999
Revised: 31 January 2000
Published online: 15 August 2000

Abstract

The isotope shift (IS) and hyperfine structure (hfs) of nine levels (31720 to 38921 cm^-1) assigned to the configuration in neutral erbium have been determined experimentally using Doppler-reduced saturation absorption spectroscopy in a gas discharge. We performed a fine structure analysis in the SL-coupling scheme of the single configuration , confirming and extending the classification of even parity Er I levels. We discriminated the different hfs contributions of the core and the (6s+7s) outer electrons of the shell in a non-relativistic JJ-coupling approach and in the relativistic effective tensor operator formalism in SL-coupling. The relativistic one-electron parameters of the hfs for ¹⁶⁷Er were fitted to the experimental data by a least squares fit procedure: 0pt[0pt] MHz, 0pt[0pt] MHz, 0pt[0pt] MHz. The level dependencies of the isotope shift were evaluated based on crossed second order (CSO) effects. We obtained the following results for the CSO parameters for the isotope pairs ^170-168Er:  MHz,  MHz,  MHz and for ^170-166Er:  MHz,  MHz,  MHz. The resulting parameters for the hfs are compared with those known for other configurations of the Er atom and ion.