Isotope Shift in the Spectrum of Erbium I

Abstract

Using enriched samples, the isotope shift in seven lines of the arc spectrum of erbium was measured with a Fabry-Perot interferometer. The average relative isotope shift for the even isotopic pairs $\Delta \nu \mathrm{}(170-168):\Delta \nu \mathrm{}(168-166):\Delta \nu \mathrm{}(166-164):\Delta \nu \mathrm{}(164-162)\mathrm{}$ was found to be 1.00:096±0.02:0.94±0.03:1.23±0.04, showing a large change in nuclear deformation between the isotopes with neutron numbers 96 and 94. This results in a predicted intrinsic quadrupole moment for ${\mathrm{Er}}^{162}$ of 6.30±0.30 b. No pronounced even-odd staggering was observed for the odd isotope ${\mathrm{Er}}^{167}$, since the average value for $\Delta \nu \mathrm{}(168-166):\Delta \nu (168-167\mathrm{}\mathrm{cg})$ was found to be 1.00:0.52±0.03.