Isotope shift studies in the first spectrum of ytterbium

Isotope shift △σ (172–176) have been measured in 172 lines of the first spectrum of ytterbium in the region 3900–6500 Å employing a recording Fabry—Perot spectrometer and highly enriched isotopes excited in liquid-air-cooled hollow cathodes. Out of the 172 lines studied, energy level classifications are available for 167 of them. Isotope shift △T (172–176) of 62 even and 59 odd energy levels of Yb I have been evaluated and their electronic configurations discussed.