Reorientation-effect measurement of the 〈2+1||Ê2||2+1 matrix element in 10Be.

The highly-efficient and segmented TIGRESS y-ray spectrometer at TRIUMF has been used to perform a reorientation-effect Coulomb-excitation study of the 2+ state at 3.368 MeV in l0Be. This is the first Coulomb-excitation measurement that enables one to obtain information on diagonal matrix elements for such a high-lying first excited state from y-ray data. With the availability of accurate lifetime data, a value of --0.110 ± 0.087 eb is determined for the 〈2+1||Ê2||2+1|〉 diagonal matrix element, which assuming the rotor model, leads to a negative spectroscopic quadrupole moment of Qs(2+1) = --0.083 ± 0.066 eb. This result is in agreement with both no-core shell-model calculations performed in this work with the CD-Bonn 2000 two-nucleon potential and large shell-model spaces, and Green's function Monte Carlo predictions with two- plus three-nucleon potentials. [ABSTRACT FROM AUTHOR]