B(E1) strengths from Coulomb excitation of Be-11

Abstract

The B(E1; 1/2(+) --> 1/2(-)) strength for Be-11 has been extracted from intermediate energy Coulomb excitation measurements, over a range of beam energies using a new reaction model, the extended continuum discretized coupled channels (XCDCC) method. In addition, a measurement of the excitation cross section for Be-11 + Pb-208 at 38.6 MeV/nucleon is reported. The B(E1) strength of 0.105(12) e(2) fm(2) derived from this measurement is consistent with those made previously at 60 and 64 MeV/nucleon, in contrast to an anomalously low result obtained at 43 MeV/nucleon. By coupling a multi-configuration description of the projectile structure with realistic reaction theory, the XCDCC model provides for the first time a fully quantum mechanical description of Coulomb excitation. The XCDCC calculations reveal that the excitation process involves significant contributions from nuclear, continuum, and higher-order effects. An analysis of the present and two earlier intermediate energy measurements yields a combined B(E1) strength of 0.105(7) e(2) fm(2). This value is in good agreement with the value deduced independently from the lifetime of the 1/2(-) state in Be-11, and has a comparable precision. (C) 2007 Elsevier B.V. All rights reserved.

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