#### Abstract

The ${}_{}{}^{14}{}_{}{}^{}\mathrm{Be}$ nucleus is investigated in the three-cluster generator coordinate method, involving several ${}_{}{}^{12}{}_{}{}^{}\mathrm{Be}$+*n*+*n* configurations. The ${}_{}{}^{12}{}_{}{}^{}\mathrm{Be}$ core nucleus is described in the harmonic oscillator model with all possible configurations in the *p* shell. We present the theoretical energy spectrum of ${}_{}{}^{14}{}_{}{}^{}\mathrm{Be}$ up to 5 MeV excitation energy, and show that the matter densities support a halo structure of the ground state. A strong enhancement of the rms radius with respect to the ${}_{}{}^{12}{}_{}{}^{}\mathrm{Be}$ core is obtained, in agreement with experiment. Our calculation indicates that the ${}_{}{}^{12}{}_{}{}^{}\mathrm{Be}$ (g.s.)+*n*+*n* configuration represents 66% only of the total wave function, and that core excitations cannot be neglected. A comparative study of the ${}_{}{}^{12}{}_{}{}^{}\mathrm{Be}$, ${}_{}{}^{13}{}_{}{}^{}\mathrm{Be}$, and ${}_{}{}^{14}{}_{}{}^{}\mathrm{Be}$ nuclei is performed with identical conditions of calculation. We also analyze dipole and quadrupole excitations of the ${}_{}{}^{14}{}_{}{}^{}\mathrm{Be}$ ground state, and show that a significant part of the sum rules for soft modes is exhausted at low excitation energies.

DOI: http://dx.doi.org/10.1103/PhysRevC.52.704

- Received 23 February 1995
- Published in the issue dated August 1995

© 1995 The American Physical Society