Search for α condensed states in 13C using α inelastic scattering

Abstract

We searched for the α condensed state in 13C by measuring the α inelastic scattering at Eα = 388MeV at forward angles including 0?. We performed a distorted-wave Born approximation calculation with the single-folding potential and multipole decomposition analysis to determine the isoscalar transition strengths in 13C.We found a bump structure around Ex = 12.5MeV due to the isoscalar monopole (IS0) transition.A peak-fit analysis suggested that this bump consisted of several 1/2- states. We propose that this bump is due to the mirror state of the 13.5MeV state in 13N, which dominantly decays to the α condensed state in 12C. It was speculated that the 1/2- states around Ex = 12.5MeV were candidates for the α condensed state, but the 3α +n orthogonality condition model suggests that the α condensed state is unlikely to emerge as the negative parity states.We also found two 1/2+ or 3/2+ states at Ex = 14.5 and 16.1MeV excited with the isoscalar dipole (IS1) strengths.We suggest that the 16.1MeV state is a possible candidate for the α condensed state predicted by the cluster model calculations on the basis of the good correspondence between the experimental and calculated level structures. However, the theoretical IS1 transition strength for this state is significantly smaller than the measured value. Further experimental information is strongly desired to establish the α condensed state in 13C.