Double Coulomb Excitation with Oxygen Ions

Total cross sections for Coulomb excitation of the first and second excited states of the ground-state rotational bands of eight even-even rare earth nuclei have been measured. Oxygen ions accelerated to energies in the range 14 to 50 MeV in the Wisconsin tandem accelerator produced the nuclear excitations. The transitions from the second excited state ($4^{+}$) to the first ($2^{+}$), and from the first to the ground state ($0^{+}$), were detected by analyzing the emitted internal conversion electrons in a wedge-shaped magnetic beta-ray spectrometer. Cross sections for excitation of the $2^{+}$ levels yield $B\left(E2\mathrm{}\right)\mathrm{}$ values in satisfactory agreement with those obtained from lifetime measurements and from inelastic scattering of protons, deuterons, and alpha particles. Cross sections for double $E2\mathrm{}$ excitation of the $4^{+}$ levels are in qualitative agreement with the multiple Coulomb excitation theory of Alder and Winther. The energies of the $4^{+}$ levels are ${\mathrm{Sm}}^{152}$, 366.2 keV; ${\mathrm{Sm}}^{154}$, 267.1 keV; ${\mathrm{Gd}}^{160}$, 248.6 keV; ${\mathrm{Dy}}^{162}$, 266.0 keV; ${\mathrm{Er}}^{170}$, 261.5 keV; ${\mathrm{Yb}}^{176}$, 271.9 keV; ${\mathrm{Hf}}^{180}$, 309.4 keV; and ${\mathrm{W}}^{184}$, 363.4 keV. In all cases the uncertainty is ±2 keV.