Figure 1

Experimentally deduced fractional Doppler shifts $F\left(\tau \right)$, as a function of $\gamma$-ray energy for the SD bands assigned to ${}^{89}\mathrm{Tc}$ (left panel) and ${}^{91}\mathrm{Tc}$ (right panel) are indicated by the circles. $F\left(\tau \right)$ is defined as the ratio between the average velocity that the nuclei have when emitting a certain $\gamma$ ray and the average initial velocity of the nuclei. The velocity as a function of $\gamma$-ray energy was obtained from the residual Doppler shift of the $\gamma$ rays after a partial Doppler correction (using a constant velocity as a function of energy) has been made. Transitions between known ND states in ${}^{88}\mathrm{Mo}$ are included for comparison (squares). The error bars show only the statistical uncertainties. For ${}^{89}\mathrm{Tc}$, the solid line corresponds to $Q_t=5.9e\mathrm{b}$ and the dashed lines to $Q_t=5.6$ and $6.6e\mathrm{b}$ (corresponding to the uncertainties given in Table ). For ${}^{91}\mathrm{Tc}$, these values are $Q_t=6.7,5.9$, and 8.0. The dotted line has been included for comparison and corresponds to $Q_t=3.5e\mathrm{b}$ in both cases.Reuse & Permissions

Figure 2

Spectrum produced by summing all combinations of triple gates on the transitions of the SD band in ${}^{89}\mathrm{Tc}$ for events where two $\alpha$ particles and one or zero protons were detected. A filter based on the total detected energy and the $\gamma$ ray multiplicity has been applied to the data, and relevant background contributions have been subtracted. The inset compares spectra for the total energy of the charged particles detected in coincidence with transitions from the SD band (SD) and lower-lying transitions (ND). As expected, the average energy of the emitted charged particles is lower when the SD band is populated. The unusually strong relative intensity of the SD band in this nucleus reveals itself as the “bump” in the “ND” particle energy spectrum. Compare, e.g., with the same picture for ${}^{91}\mathrm{Tc}$ (see Fig. 3), where this feature is not present. Transitions assigned to the SD band are indicated by filled circles, and transitions between lower-lying states in the same nucleus are indicated by triangles.Reuse & Permissions

Figure 3

Spectrum obtained by summing all combinations of triple gates on the transitions in the SD band in ${}^{91}\mathrm{Tc}$ in coincidence with $1\alpha 3p,1\alpha 2p$, or $1\alpha 1p$, and subtracting a background spectrum. A gate criterion on the total detected energy and $\gamma$-ray multiplicity was also applied. In the inset the total energy distribution of the charged particles detected in coincidence with the SD band is compared with a distribution in coincidence with known lower-lying transitions in the same nucleus. Transitions connecting states in the SD band are marked by circles, and previously established transitions between lower-lying states are indicated by triangles.Reuse & Permissions

Figure 4

Background subtracted spectra showing the SD bands (bands 1 and 2) of ${}^{88}\mathrm{Mo}$ discussed in this article. The spectra have been obtained by applying double gates on the in-band transitions. Two $\alpha$ particles and one or two protons were required in coincidence with the $\gamma$ rays. In addition, the events were subject to a simultaneous criterion applied to the total detected $\gamma$-ray multiplicity and total detected energy, in order to further filter out any contaminants emanating from other reaction channels. Transitions assigned to the SD bands are indicated by circles, and previously established lower-lying transitions by triangles.Reuse & Permissions

Figure 5

Experimental dynamical ${\mathcal{J}}^{\left(2\right)}$ moments of inertia for the SD bands discussed in this work plotted as a function of rotational frequency. Note the very high ${\mathcal{J}}^{\left(2\right)}$ moment of inertia for the band assigned to ${}^{91}\mathrm{Tc}$ and the irregularity in the curve that may indicate a band crossing. Statistical uncertainties are indicated by the error bars.Reuse & Permissions

Figure 6

Experimentally deduced transition quadrupole moments divided by $Z{A}^{2∕3}$ as a function of $Z$ for the SD bands in the neutron-deficient $A\approx 80–90$ mass region are shown with error bars. The data points have been offset slightly from the corresponding $Z$ value for improved readability. The dashed line shows the quadrupole moment as defined by the simple relation 1, where ${\beta }_2$ is taken as the predicted mean SD shell gap deformations (see, e.g., Fig 7). The tendency of a systematically increasing $Q_t$ and ${\beta }_2$ deformation as a function of $Z$ present in the data is reproduced by the simple theoretical model.Reuse & Permissions

Figure 7

Woods-Saxon single-proton diagram as a function of ${\beta }_2$ deformation, valid for $Z\approx 40$, at a rotational frequency of $\hslash \omega =0.8\text{MeV}$. Proton numbers for the largest shell gaps and intruder orbitals emanating from the $\mathcal{N}=5$ and 6 shells are indicated in the figure. The symbols for the different $\left(\pi ,\alpha \right)$ configurations: solid, $\left(+,\frac{1}{2}\right)$; dotted: $\left(+,-\frac{1}{2}\right)$, dash dotted: $\left(-,\frac{1}{2}\right)$; and dashed, $\left(-,-\frac{1}{2}\right)$.Reuse & Permissions