Y. Zheng, G. de France, E. Clément, A. Dijon, B. Cederwall, R. Wadsworth, T. Bäck, F. Ghazi Moradi, G. Jaworski, B. M. Nyakó, J. Nyberg, M. Palacz, H. Al-Azri, G. de Angelis, A. Atac, Ö. Aktaş, S. Bhattacharyya, T. Brock, P. J. Davies, A. Di Nitto, Zs. Dombradi, A. Gadea, J. Gal, P. Joshi, K. Juhasz, R. Julin, A. Jungclaus, G. Kalinka, J. Kownacki, G. La Rana, S. M. Lenzi, J. Molnar, R. Moro, D. R. Napoli, B. S. Nara Singh, A. Persson, F. Recchia, M. Sandzelius, J. -N. Scheurer, G. Sletten, D. Sohler, P. -A. Söderström, M. J. Taylor, J. Timar, J. J. Valiente-Dobon, E. Vardaci
Linear polarization measurements have been performed for $\gamma$-rays in $^{91}$Ru produced with the $^{58}$Ni($^{36}$Ar, $2p1n$$\gamma$)$^{91}$Ru reaction at a beam energy of 111 MeV. The EXOGAM Ge clover array has been used to measure the $\gamma$-$\gamma$ coincidences, $\gamma$-ray linear polarization and $\gamma$-ray angular distributions. The polarization sensitivity of the EXOGAM clover detectors acting as Compton polarimeters has been determined in the energy range 0.3$-$1.3 MeV. Several transitions have been observed for the first time. Measurements of linear polarization and angular distribution have led to the firm assignments of spin differences and parity of high-spin states in $^{91}$Ru. More specifically, calculations using a semi-empirical shell model were performed to understand the structures of the first and second (21/2$^{+}$) and (17/2$^{+}$) levels. The results are in good agreement with the experimental data, supporting the interpretation of the non yrast (21/2$^{+}$) and (17/2$^{+}$) states in terms of the $J_{\rm max}$ and $J_{\rm max}-2$ members of the seniority-three $\nu(g_{9/2})^{-3}$ multiplet.
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http://arxiv.org/abs/1304.3287
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