Quasi-SU(3) truncation scheme for odd-even sd-shell nuclei
  The quasi-SU(3) symmetry, as found in shell model calculations, refers to the dominance of the single particle plus quadrupole-quadrupole terms in the Hamiltonian used to describe well deformed nuclei, and to the subspace relevant in its diagonalization. It provides a very efficient basis truncation scheme. It is shown that a small number of SU(3) coupled irreps, those with the largest C_2 values within the direct product of the proton and neutron SU(3) irreps with spin 0 and 1 (for even number of particles), and spin 1/2 and 3/2 for (for odd number of nucleons), are enough to describe the low energy spectra and B(E2) transition strengths of 21Ne, 23Na and 25Mg. A simple but realistic Hamiltonian is employed. Results compare favorably both with experimental data and with full shell model calculations. Limitations and possible improvements of the schematic Hamiltonian are discussed. 
C. E. Vargas (1), J. G. Hirsch (2), and J. P. Draayer (3)   ((1)CINVESTAV-Mexico, (2)ICN-Unam-Mexico, (3) Lsu-Us)