The application of the Su(3) shell model to 9Be

Abstract

The normal and non-normal parity levels, as well as the static properties of the ground state, of 9Be are investigated using the Elliott SU(3) shell model. The model predicts that the non-normal (i.e., positive) parity levels from a K = 1 2 rotational band. Three different normal-parity energy level schemes are proposed, and it is shown that they each, to a good approximation, are composed of a K = 3 2 band and a K = 1 2 band. Each of the three normal-parity schemes involve an approximate degeneracy. For all three energy level schemes the calculated ground state quadrupole moment is in excellent agreement with experiment and does not aid in distinguishing between them. On the other hand, the ground state magnetic moment does depend significantly on the particular scheme chosen and favours a scheme that has a degeneracy at 2.50 MeV involving two levels with spin and parity assignment 1 2 − and 5 2 − , respectively. The conclusion is reached that the SU(3) shell model is capable of describing the 9Be nucleus, and it is suggested that the normal-parity energy level scheme with the 1 2 − , 5 2 − degeneracy is involved in this description. Finally, the results of some photodisintegration calculations are reported, which tend to confirm the preceding conclusion.