Single-particle excitations in the level structure of ${}^{64}\mathrm{Cu}$

Excited states of the ${}^{64}\mathrm{Cu}(Z=29,N=35)$ nucleus have been probed using heavy-ion-induced fusion evaporation reaction and an array of Compton-suppressed Clovers as detection system for the emitted $\gamma$ rays. More than 50 new transitions have been identified and the level scheme of the nucleus has been established up to an excitation energy $E_x\sim 6$ MeV and spin $\sim 10\hslash$. The experimental results have been compared with those from large-basis shell-model calculations that facilitated an understanding of the single-particle configurations underlying the level structure of the nucleus.

Figure 1

Part of the projection spectrum constructed out of the present data illustrating the different nuclei populated in the experiment.

Figure 2

$R_{ADO}$ values for different transitions of ${}^{64}\mathrm{Cu}$ along with those of selected transitions of previously known multipolarities from other nuclei populated in the present experiment. The latter is used to fix the reference values used in the current analysis as well as for validation of the same.

Figure 3

(Upper panel) Plot of the geometrical asymmetry ($a$) against $\gamma$-ray energies along with the fit to the data points using the equation $a_0+a_1{E}_{\gamma }$. (Lower panel) Plot of polarization asymmetry $\mathrm{\Delta }$ [defined in Eq. (2)] for different $\gamma$-ray transition in ${}^{64}\mathrm{Cu}$ along with those in other dominantly produced nuclei in the same experiment, included as reference.

Figure 4

(Upper panel) Plot of polarization sensitivity as a function of $\gamma$-ray energy, determined from the observed $\gamma$ rays of previously known multipole mixing ratio, along with the fit using Eq. (5). (Lower panel) Plot of polarization $P$, defined in Eq. (4), for different $\gamma$-ray transitions of ${}^{64}\mathrm{Cu}$ and other nuclei populated in the present experiment. The latter are of previously known multipole mixing that were used to calculate their theoretical polarization, included in the plot, for reference and validation of the current analysis.

Figure 5

Level scheme of the ${}^{64}\mathrm{Cu}$ nucleus from the present work. The new $\gamma$-ray transitions identified from the current study are marked with * and labeled in red. The transitions labeled in blue were observed in the previous studies but were either not placed in the level scheme or had different placement with respect to the energy and/or $J^{\pi }$ values of the de-exciting states.

Figure 6

Representative spectra with gate on $\gamma$-ray transitions of ${}^{64}\mathrm{Cu}$. The new transitions, first observed in the present study, are labeled with an asterisk (*).

Figure 7

Sum spectrum of $\gamma \text{−}\gamma$ gates, applied on the $\gamma \text{−}\gamma \text{−}\gamma$ cube, from a list of transitions, 203, 212, 1019, 784, 813, 609, and 1597 keV, that illustrates the high-energy $\gamma$ rays of ${}^{64}\mathrm{Cu}$.

Figure 8

Comparison between the experimental and calculated (SM) level energies of ${}^{64}\mathrm{Cu}$.