$0_2^{+}$ band in ${}^{102}\mathrm{Ru}$ and the evolution of nuclear deformation in Ru isotopes

Two measurements of $\gamma$ rays from the slow-neutron capture reaction on a ${}^{101}\mathrm{Ru}$ target were performed at the PF1B cold-neutron facility and the DuMond GAMma Spectrometer GAMS5 of ILL Grenoble, to study in detail excitations in the transitional nucleus ${}^{102}\mathrm{Ru}$. A band structure on top of the $0_2^{+}$ level has been identified and its nature is discussed. Mixing between the $0_1^{+}$ and $0_2^{+}$ levels in Ru isotopes with $50<N<66$ neutrons and its role in the development of deformation in the ground state of the Ru nuclei have been studied.

Figure 1

Partial level scheme of ${}^{102}\mathrm{Ru}$ as observed in the present work. New levels are marked with an asterisk. More accurate level and transition energies are given in Table .

Figure 2

Singles-$\gamma$ spectrum from GAMS5, measured in the third diffraction order. In the picture one channel corresponds to 100 eV. The energy scale has been adjusted to reproduce the energy of the 475.095(1)-keV reference line [16], with accuracy of 0.003 keV.

Figure 3

Systematics of $0_2^{+}$ bands in Ru isotopes. The $2_1^{+}$ and $4_1^{+}$ levels are also shown to assist further discussion (see the text). Lines are drawn to guide the eye. The data are taken from Refs. [16, 20, 23, 24, 25, 26, 27, 28].

Figure 4

Positions of $0_1^{+}$ and $0_2^{+}$ levels (full dots), relative to the $2_1^{+}$ phonon excitation (open dots) in Ru isotopes. Solid lines represent a two-level mixing calculation. Symbols shown in the figure are explained in the text.

Figure 5

Exchange of properties between the crossing $0_1^{+}$ and $0_2^{+}$ levels, as simulated in two-level mixing calculation. See text for the explanation of $D_1$ and $D_2$ and further comments.