Collectivity of neutron-rich Cr and Fe toward N=50

• Main Authors: Werner V., Santamaria C., Louchart C., Obertelli A., Doornenbal P., Nowacki F., Authelet G., Baba H., Calvet D., Château F., Corsi A., Delbart A., Gheller J.-M., Gillibert A., Isobe T., Lapoux V., Matsushita M., Momiyama S., Motobayashi T., Niikura M., Otsu H., Péron C., Peyaud A., Pollacco E.C., Roussé J.-Y., Sakurai H., Sasano M., Shiga Y., Takeuchi S., Taniuchi R., Uesaka T., Wang H., Yoneda K., Browne F., Chung L.X., Dombradi Zs., Franchoo S., Giacoppo F., Gottardo A., Hadynska-Klek K., Korkulu Z., Koyama S., Kubota Y., Lee J., Lettmann M., Lozeva R., Matsui K., Miyazaki T., Nishimura S., Olivier L., Ota S., Patel Z., Pietralla N., Sahin E., Shand C., Söderström P.-A., Stefan I., Steppenbeck D., Sumikama T., Suzuki D., Vajta Zs., Wu J., Xu Z.
• Format: Article
• Language: English
• Published: EDP Sciences 2016-01-01
• Series: EPJ Web of Conferences
• Online Access: http://dx.doi.org/10.1051/epjconf/201610703007

Within the SEASTAR project at RIKEN-RIBF, 66Cr and 70,72Fe have been produced via protonknockout reactions, and their first excited 2+ and 4+ states have been discovered. The combination of the liquid-hydrogen target and TPC system MINOS has been used in combination with the DALI2 detector array for the first time. A 345 MeV/u 238U beam with a mean intensity of about 12 pnA impinged on a Be target. Fission fragments were separated and identified using the BigRIPS spectrograph, and reaction products were analyzed using the ZeroDegree spectrograph. A plateau of excitation energies, with a small change in the systematic trends past N = 44, reveals an extension of the N = 40 region of collectivity toward N = 50. Hence, the isotopes of interest are located within the N = 40 island of inversion. An interpretation of the observed trends is offered through large scale shell model calculations.