Quadrupole-quadrupole interaction calculations which include N=2 mixing

Abstract

We carry out a study of the study of the $Q\cdot Q$ interaction in a model space which consists of several nucleons in an open shell and all $2\hslash \omega$ excitations. This interaction is $-t(X_o/2)Q\cdot Q$, where for t=1 we get the `accepted strength'. In the $0p$ space, the spectrum would scale with $t$. In this space, the $2_1^{+}$ and $2_2^{+}$ states of ${}^{10}$Be are degenerate, as are the [330] and [411] sets of $J=0^{+},1^{+}$ and $2^{+}$ triplets. When $2\hslash \omega$ admixtures are included, the degeneracies are removed. For $t\ge 1.8$ we have new ground state and a new $2_1^{+}$ state. These are states in which two particles are excited from the $0p$ to the $1s-0d$ shell. There is no mixing of these 2p-2h states with the other states. For these 2p-2h states the occupancy for 0s,0p,1s-0d and 1p-of are 4,4,2 and 0 respectively.

Comments: 15 pages, RevTeX (3.0), 2 figures available from elaine@physics.rutgers.edu