Deformed state admixtures in¹⁸O

Following the suggestion by Brown, we have considered a model of the nucleus 18 O in which, in addition to the usual shell-model picture of two neutrons coupled to an inert 16 O core, we have also included a collective deformed state represented by a two-proton excitation in a deformed but axially symmetric shell-model potential. For a given model interaction (the Kallio-Kolltveit interaction), four fitted parameters (the oscillator constant, the effective charge and the single-particle spectrum) and two variational parameters (the deformation parameters) we have managed to reproduce the lowest eight known positive parity states to a good approximation in 18 O and the two principal E2 transition rates. The predicted eigenvectors are in good agreement with the stripping experiments of Moreh and Daniels.