gamma$-ray linear polarization measurements and $(g_{9/2})^{-3}$ neutron alignment in $^{91}$Ru

• Main Authors: Zheng, Y, de France, G, Clément, E, Dijon, A, Cederwall, B, Wadsworth, R, Bäck, T, Moradi, F. Ghazi, Jaworski, G, Nyakó, B. M, Nyberg, J, Palacz, M, Al-Azri, H, de Angelis, G, Atac, A, Aktaş, Ö, Bhattacharyya, S, Brock, T, Davies, P. J, Di Nitto, A, Dombradi, Zs, Gadea, A, Gal, J, Joshi, P, Juhasz, K, Julin, R, Jungclaus, A, Kalinka, G, Kownacki, J, La Rana, G, Lenzi, S. M, Molnar, J, Moro, R, Napoli, D. R, Singh, B. S. Nara, Persson, A, Recchia, F, Sandzelius, M, Scheurer, J. -N, Sletten, G, Sohler, D, Söderström, P. -A, Taylor, M. J, Timar, J, Valiente-Dobon, J. J, Vardaci, E
• Format: Journal Article
• Language: English
• Published: 11.04.2013
• Subjects: Physics - Nuclear Experiment
• DOI: 10.48550/arxiv.1304.3287

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.