Eur. Phys. J. Special Topics 150, 99-102 (2007)
https://doi.org/10.1140/epjst/e2007-00277-5

Study of N=20 shell gap with ¹H(²⁸Ne,^27,28Ne) reactions

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: 31 January 2007
Published online: 8 December 2007

Abstract

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 M_n=13.8 ±3.7 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.