Observation of He 6 +t cluster states in Li 9

Two resonant states above the He6+t threshold in Li9 have been observed using a Li9 beam bombarding a Pb208 target at the incident energy of 32.7 MeV/nucleon. An angular correlation analysis and the continuum discretized coupled channels (CDCC) method have been applied to identify the spin-parities of observed resonant states. The obtained results from the present methods of calculations indicate the first resonant state at 9.8 MeV with a spin-parity of 3/2-. The second resonant state at 12.8 MeV with limited statistics might suggest the spin-parity of 7/2-, which needs to be further investigated. The monopole matrix element of the 3/2- state is extracted as 8.1(8) fm2 with a multipole decomposition analysis based on a distorted wave Born approximation (DWBA) calculation. These results give the first experimental evidence supporting the theoretical prediction of the generator coordinate method (GCM) and disclose the feature of clustering structure involving two neutron-rich clusters in the neutron-rich nucleus Li9.