Abstract
This Letter reports on the and reactions studied at intermediate energy using a liquid hydrogen target. From the cross section populating the first excited state of , and using the previously determined value, the neutron quadrupole transition matrix element has been calculated to be . In the neutron knockout reaction, two low-lying excited states were populated in . Only one of them can be interpreted by the shell model while the additional state may intrude from the shell. These experimental observations are consistent with the presence of shell configurations at low excitation energy in nuclei caused by a vanishing shell gap at .
- Received 13 July 2005
DOI:https://doi.org/10.1103/PhysRevLett.96.182501
©2006 American Physical Society