Figure 1

Gamma-ray spectra of $N=60$ isotones, as obtained in the induced fission of ${}^{238}\mathrm{U}$. The spectra were obtained with the CLARA $\gamma$-ray array, and were gated by the specified isotopes, detected and identified with the PRISMA spectrometer. The presented spectra have 2 keV per channel.Reuse & Permissions

Figure 2

Systematics of the $E(2_1^{+})$ values in different isotopic chains in the $A\approx 100$ region (left), as well as of the $E(2_1^{+})$ and $E(4_1^{+})$ energies as a function of $Z$ for Kr, Sr, Zr, Mo (right).Reuse & Permissions

Figure 3

Quadrupole deformation ${\beta }_2$ values in the neutron-rich Kr, Sr, and Zr isotopes. The black circles are values deduced from the experimental $B(E2;2_1^{+}\to 0_{\mathrm{g}.\mathrm{s}.}^{+})$ values (from Ref. [14] for ${}^{88}\mathrm{Kr}$ and ${}^{92}\mathrm{Kr}$, and Ref. [24] for the rest of the nuclei). The hatched area is the domain predicted by the empirical formula of Raman et al. [25], given in the text.Reuse & Permissions

Figure 4

Comparison of experimental and theoretically predicted quadrupole deformations in the $N=60$ Kr, Sr, Zr, and Mo isotones. For ${}^{96}\mathrm{Kr}$ the experimental deformation (the hatched rectangle) is the value calculated with the Raman's formula. For each isotone we represent the predictions of five theoretical calculations, drawn as sticks at the abscissas $Z-0.2,Z-0.1,\dots ,Z+0.2$, corresponding, respectively, to the following references: [4, 15] (Nilsson-Strutinsky), [19] (RMF), [17] (FRDM), [18] (ETF-SI). When there was a strong prolate-oblate competition the solutions of both signs are represented (this is notably the case of Kr).Reuse & Permissions