Energy Levels of Er167, Er169, and Er171 from (d, p) Reactions

Abstract

High-resolution ($d, p$)-reaction spectroscopy has been used to study the energy levels of ${\mathrm{Er}}^{167}$, ${\mathrm{Er}}^{169}$, and ${\mathrm{Er}}^{171}$ to excitation energies greater than 2.5 MeV. The energy resolution for proton groups observed in a magnetic spectrograph was ≈0.08%. The measured $Q$ values are 4209±10, 3773±10, and 3450±10 keV for ${\mathrm{Er}}^{166}(d, p){\mathrm{Er}}^{167}$, ${\mathrm{Er}}^{168}(d, p){\mathrm{Er}}^{169}$, and ${\mathrm{Er}}^{170}(d, p){\mathrm{Er}}^{171}$ reactions, respectively. A large number of the observed energy levels have been assigned to specific Nilsson orbitals and their superimposed rotational bands. Generally, the energy systematics of the Nilsson bands qualitatively follow expectations of the Nilsson model. The energy systematics, decoupling parameters, and cross sections suggest considerable mixing between $\gamma$-vibrational bands and certain Nilsson states with the same spin and parity. The strongest indications in these data for mixings of collective and intrinsic states involve the ½-[510] band. In ${\mathrm{Er}}^{167}$ and ${\mathrm{Er}}^{169}$, this band appears to be considerably lowered from the position expected by energy systematics, and appears to have a lower cross section than expected for a pure ½-[510] band.