Spectroscopy of the neutron-deficient $N=50$ nucleus ${}^{95}\mathrm{Rh}$

The neutron-deficient semimagic (neutron number $N=50$) ${}^{95}\mathrm{Rh}$ nucleus has been produced at high spins using the projectile-target system ${}^{40}\mathrm{Ca}+{}^{58}\mathrm{Ni}$ at 125 MeV beam energy. The $\gamma$-decays of levels populated by the $3p$ fusion evaporation reaction channel were studied using $\gamma \text{−}\gamma$ coincidences, and 20 new $\gamma$-ray transitions involving 15 new positive- and negative-parity states were observed. Spin and parity for many of the excited states were firmly deduced for the first time using the combined directional angular correlation and direction-polarization techniques. The observed structures are discussed within the framework of large-scale shell model calculations. $E1$ transition strengths were deduced and used together with the results of the shell model calculations to study the contribution of different particle-hole configurations, in particular for analyzing contributions from core-excited configurations.

Figure 1

Partial level scheme of ${}^{95}\mathrm{Rh}$. The low energy part, up to $\sim$3 MeV of excitation energy, is identical to the level scheme previously reported in Ref. [2]. The arrows mark the observed $\gamma$-ray transitions with their energy given in keV. The widths of arrows are proportional to the measured intensities.

Figure 2

Gamma-ray coincidence energy spectra gated on the new 2038 keV (a), the 1031 keV (b), and the previously known [2] 1250 keV (c) transitions in ${}^{95}\mathrm{Rh}$.

Figure 3

Polarization measurement for $\gamma$ rays in ${}^{95}\mathrm{Rh}$. The spectrum is selected with a coincidence requirement of three protons detected in the DIAMANT detectors. Gamma-ray lines from the four-proton reaction channel belonging to ${}^{94}\mathrm{Ru}$ (marked by filled circles) are present due to the limited detection efficiency for protons. See Ref. [13] for details.

Figure 4

Linear polarization, $P$, vs angular correlation measurement of $\gamma$ rays in ${}^{95}\mathrm{Rh}$. The stretched $M1$, stretched $E2$, stretched $E1$, and nonstretched $E1$ data points are shown in circles, squares, triangles, and stars, respectively. The color code shows the assigned multipolarity. Blue is stretched $E1$, red is stretched $M1$, green is stretched $E2$, and purple is nonstretched transition ($\Delta I=0$). A selection of transitions of interest are labeled by their energy values in keV (see text).

Figure 5

Comparison between some observed excitation energies and shell model calculations in the $fpg$ and $fpgd$ model spaces for ${}^{95}\mathrm{Rh}$.