부산대학교 도서관

We searched for the [alpha] condensed state in [.sup.13]C by measuring the [alpha] inelastic scattering at [E.sub.[alpha]] = 388 MeV at forward angles including 0[degrees]. We performed a distorted-wave Born approximation calculation with the single-folding potential and multipole decomposition analysis to determine the isoscalar transition strengths in [.sup.13]C. We found a bump structure around [E.sub.x] = 12.5 MeV due to the isoscalar monopole (IS0) transition. A peak-fit analysis suggested that this bump consisted of several [1/2.sup.-] states. We propose that this bump is due to the mirror state of the 13.5 MeV state in [.sup.13]N, which dominantly decays to the [alpha] condensed state in [.sup.12]C. It was speculated that the [1/2.sup.-] states around [E.sub.x] = 12.5 MeV were candidates for the [alpha] condensed state, but the 3[alpha] + n orthogonality condition model suggests that the [alpha] condensed state is unlikely to emerge as the negative parity states. We also found two [1/2.sup.+] or [3/2.sup.+] states at [E.sub.x] = 14.5 and 16.1 MeV excited with the isoscalar dipole (IS 1) strengths. We suggest that the 16.1 MeV state is a possible candidate for the [alpha] 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 IS 1 transition strength for this state is significantly smaller than the measured value. Further experimental information is strongly desired to establish the [alpha] condensed state in [.sup.13]C. Subject Index D05, D11, D22
1. Introduction [alpha]-cluster structures are well known to appear in atomic nuclei. Cluster structures develop in nuclei when their energies are close to the cluster-decay thresholds. This threshold rule is [...]