FINE AND HYPERFINE-STRUCTURE FOR 4F(11)5D6S6P IN ERL

Hyperfine structure (hfs) constants in neutral erbium of 22 levels of the configuration 4f(11)5d6s6p with four open electron shells have bee n determined for the only stable odd isotope Er-167, using Doppler red uced saturation spectroscopy in form of intermodulated optogalvanic an d saturated absorption spectroscopy. From the experimental data for al together 29 levels we evaluated the hfs-parameters in the effective te nser operator formalism. For this purpose we performed a fine structur e analysis of the sub-configuration 4f(11)(I-4)5d6s6p in LS-coupling, confirming and extending the preliminary classification of even parity ErI levels. The relativistic magnetic and electric one-electron param eters were fitted to the experimental data by a least squares fit proc edure: a(4f)(01)= -156.6(1.7)MHz, a(5d)(01) = -30(10)MHz, a(6p)(01)=-1 14(24)MHz, a(6s)(10)=-1630(35)MHg b(4f)(02)= -7960 (200) MHz, b(5d)(02 )= 3460 (180) MHz, b(6p)(02) = 5440 (270) MHz, gave the best results i n the case where all parameters of one electron shell were held in a f ixed ratio. The corresponding <r(-3)>(kskl)(nl) values are compared wi th those known for other lanthanide elements, extending the present sy stematic hyperfine studies. Finally, effective nuclear quadrupole mome nts have been determined and will be discussed.