O+(GS) → 2+(4.44MeV) transition density in 12C

A model is proposed for the 2+ first excited state in 12C in which the dominant configurations outside the p shell are assumed to come from mixing with an 'idealised' isoscalar giant quadrupole resonance. A small admixture of this resonance is capable of reproducing the high collectivity of the first excited state and gives a reasonably good fit to inelastic electron scattering data. The model gives a possible explanation of the lack of energy-weighted E2 strength up to about 30MeV in this nucleus, and a simple extension of the model gives an overall improvement in theoretical estimates of experimental quadrupole moments in the 12C region. The folding model is used to discuss the properties of the corresponding transition and reorientation potentials for coupled-channels calculations of 12C+12C scattering. (author)