Study of N=20 shell gap with 1H(28Ne,27,28Ne) reactionsZ. Elekes1, 2, Zs. Dombrádi1, A. Saito3, N. Aoi2, H. Baba3, K. Demichi3, Zs. Fülöp1, J. Gibelin4, T. Gomi2, H. Hasegawa3, N. Imai5, M. Ishihara2, H. Iwasaki5, S. Kanno3, S. Kawai3, T. Kishida2, T. Kubo2, K. Kurita3, Y. Matsuyama3, S. Michimasa5, T. Minemura2, T. Motobayashi2, M. Notani5, T.K. Ohnishi2, H.J. Ong4, S. Ota6, A. Ozawa7, H.K. Sakai3, H. Sakurai2, S. Shimoura4, E. Takeshita3, S. Takeuchi2, M. Tamaki4, Y. Togano3, K. Yamada3, Y. Yanagisawa2 and K. Yoneda2
1 Institute of Nuclear Research of the Hungarian Academy of Sciences, P.O. Box 51, 4001 Debrecen, Hungary
2 The Institute of Physical and Chemical Research, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
3 Rikkyo University, 3 Nishi-Ikebukuro, Toshima, Tokyo 171, Japan
4 Institut de Physique Nucléaire, 15 rue Georges Clemenceau 91406 Orsay, France
5 University of Tokyo, Tokyo 1130033, Japan
6 Kyoto University, Kyoto 606-8501, Japan
7 University of Tsukuba, Tennoudai 1-1-1, Tsukuba-shi, Ibaraki 305-8571, Japan
(Received: January 31, 2007 / Published online: 8 December 2007)
This paper reports on the 1H(28Ne,28Ne) and 1H(28Ne,27Ne) reactions studied at intermediate energy using a liquid hydrogen target. From the cross section populating the first 2+ excited state of 28Ne, and using the previously determined B(E2) value, the neutron quadrupole transition matrix element has been calculated to be fm2. In the neutron knock-out reaction, two low-lying excited states were populated in 27Ne. Only one of them can be interpreted by the sd shell model while the additional state may intrude from the fp shell. These experimental observations are consistent with the presence of fp shell configurations at low excitation energy in 27,28Ne nuclei caused by a vanishing N=20 shell gap at Z=10.
25.60.-t - Reactions induced by unstable nuclei.
27.30.+t - 20(less-than-or-equal-to)A(less-than-or-equal-to)38.
29.30.Kv - X- and gamma-ray spectroscopy.
© EDP Sciences, Springer-Verlag 2007