Levels inDy164from Deuteron Stripping and Inelastic Proton Scattering Experiments

Abstract

Protons and deuterons with energies 12.5 and 12.0 MeV, respectively, were used to study the levels in ${\mathrm{Dy}}^{164}$ at a number of angles via the reactions ${\mathrm{Dy}}^{164}(p,{p}^{\ensuremath{'}}){\mathrm{Dy}}^{164}$ and ${\mathrm{Dy}}^{163}(d,p){\mathrm{Dy}}^{164}$. The ground-state $Q$ value for the latter reaction was determined as 5434\ifmmode\pm\else\textpm\fi{}5 keV. The agreement in energy between the proton groups observed in both reactions and the nuclear models of Bohr and Mottelson and Davydov allows the assignment of ground-state and gamma vibrational bands. These assignments are (in keV) G.S. (0+), 72 (2+), 240 (4+), 503 (6+), 761 (2+), 827 (3+), 919 (4+), 1040 (5+), and, with less certainty, 1157 (6+). Cross sections for excitation of the $\ensuremath{\gamma}$ band by the ($d,p$) reaction are similar to those of the G.S. band, whereas no excitation of a $\ensuremath{\beta}$ vibrational band is observed. The 6--- two-quasiparticle state, formed from the coupling of the $\frac{5}{2}$--- [523] and $\frac{7}{2}[633]$ neutron states, and 7--- member of the superimposed rotational band are probably the weak states at 1680 and 1853 keV, respectively. The 2+ two-quasiparticle state formed from the coupling of the $\frac{5}{2}$--- [523] and \textonehalf{}--- [521] neutron states and the members of the associated rotational band have probably been observed. They are: 1987 (2+), 2058 (3+), 2158 (4+), 2266 (5+), and 2418 (6+). The collective nature of the ground-state and $\ensuremath{\gamma}$ vibrational bands in ${\mathrm{Dy}}^{164}$ is clearly indicated by very small cross sections for the ($d,p$) reactions and relatively large cross sections for the ($p,{p}^{\ensuremath{'}}$) reaction. The energy gap corresponding to breaking a neutron pair is observed as a dramatic increase in the ($d,p$) cross section. A useful selection rule for ($d,p$) stripping predicted by Satchler is clearly verified experimentally.