Resonance states of 12C in a microscopic cluster model

Excited states in C-12 were theoretically investigated by means of the alpha+alpha+alpha microscopic cluster model where the complex scaling method was applied to localize the three-body resonance states. We extended the model space with respect to that by R. Pichler [Nucl. Phys. A618, 55 (1997)] by taking into account all partial waves up to the G wave in the two Jacobi coordinates and found that the 2(+) resonance excited states are significantly affected by this extension whereas the 0(+) states are insignificantly affected. The present model localizes the third 0(+) state around 4-5 MeV with respect to the three-body threshold but cannot localize the 0(+) state, which could correspond to the experimentally assumed 0(+) state at 3.0 MeV (E-x=10.3 MeV). Moreover, the second 2(+) state is localized around 2-3 MeV, which might correspond to the 2(+) state measured by M. Itoh [Nucl. Phys. A738, 268c (2004)], and the third 2(+) state is localized around 4-5 MeV, which is overlapping with the third 0(+) and the second 4(+) states.