학술논문
Coulomb and nuclear excitations of $^{70}$Zn and $^{68}$Ni at intermediate energy
Document Type
Working Paper
Author
Calinescu, S.; Sorlin, O.; Matea, I.; Carstoiu, F.; Dao, D.; Nowacki, F.; de Angelis, G.; Astabatyan, R.; Bagchi, S.; Borcea, C.; Borcea, R.; Cáceres, L.; Ciemála, M.; Clément, E.; Dombrádi, Z.; Franchoo, S.; Gottardo, A.; Grévy, S.; Guerin, H.; Harakeh, M. N.; Harca, I. M.; Kamalou, O.; Kmiecik, M.; Krasznahorkay, A.; Krzysiek, M.; Kuti, I.; Lepailleur, A.; Lukyanov, S.; Maj, A.; Maslov, V.; Mazurek, K.; Morfouace, P.; Mrazek, J.; Negoita, F.; Niikura, M.; Olivier, L.; Penionzhkevich, Y.; Perrot, L.; Petrone, C.; Podolyák, Z.; Rigollet, C; Roger, T.; Rotaru, F.; Sohler, D.; Stanoiu, M.; Stefan, I.; Stuhl, L.; Thomas, J. C.; Vajta, Z.; Vandebrouck, M.; Wieland, O.
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Subject
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Abstract
The reduced transition probabilities $B(E2; 0^+_{g.s.}\rightarrow2_1^+,2^+_2)$ in $^{70}$Zn and the full $B(E2; 0^+_{g.s.}\rightarrow2^+)$ strength up to S$_n$=7.79 MeV in $^{68}$Ni have been determined at the LISE/GANIL facility using the Coulomb-excitation technique at intermediate beam energy on a $^{208}$Pb target. The $\gamma$ rays emitted in-flight were detected with an array of 46 BaF$_2$ crystals. The angles of the deflected nuclei were determined in order to disentangle and extract the Coulomb and nuclear contributions to the excitation of the 2$^+$ states. The measured $B(E2; 0^+_{g.s.}\rightarrow2_1^+)$ of 1432(124) e$^2$fm$^4$ for $^{70}$Zn falls in the lower part of the published values which clustered either around 1600 or above 2000 e$^2$fm$^4$, while the $B(E2; 0^+_{g.s.}\rightarrow2^+_2)$ of 53(7) e$^2$fm$^4$ agrees very well with the two published values. The relatively low $B(E2; 0^+_{g.s.}\rightarrow2_1^+)$ of 301(38) e$^2$fm$^4$ for $^{68}$Ni agrees with previous studies and confirms a local magicity at $Z=28, N=40$. Combining the results of the low-energy spectra of $^{68}$Ni and $^{70}$Zn and their shell-model interpretations, it is interesting to notice that four different shapes (spherical, oblate, prolate and triaxial) are present. Finally, a summed $E2$ strength of only about 150 e$^2$fm$^4$ has been found experimentally at high excitation energy, likely due to proton excitations across the $Z=28$ gap. The experimental distribution of this high-energy $E2$ excitation agrees with SM calculations, but its strength is about two times weaker.