The di-trinucleon clustering resonances of ${}^3\mathrm{He}+{}^3\mathrm{He}$ in ${}^6\mathrm{Be}$ and $t+t$ in ${}^6\mathrm{He}$ were studied via the ${}^6\mathrm{Li}({}^3\mathrm{He},t{}^3\mathrm{He})$ and ${}^6\mathrm{Li}({}^7\mathrm{Li},{}^7\mathrm{Be}t)$ reactions at incident energies of 450 and 455 MeV, respectively. A new resonance in ${}^6\mathrm{Be}$ was found at $E_x=18.0\pm 1.2\text{MeV}$ with a width of $9.2\pm 1.0\text{MeV}$ in the binary decay channel of ${}^6\mathrm{Be}\to {}^3\mathrm{He}+{}^3\mathrm{He}$. The resonance in ${}^6\mathrm{He}$ previously reported was also observed at $E_x=18.0\pm 1.0\text{MeV}$ with a width of $9.5\pm 1.0\text{MeV}$ in the binary decay channel of ${}^6\mathrm{He}\to t+t$. The branching ratios of the resonances for each binary decay were both $0.7\pm 1.0$, which was larger than the branching ratio calculated in a statistical model by two orders of magnitude. The angular correlations measured for t and ${}^3\mathrm{He}$ particles in the binary decay show a contribution dominantly from the multipolarity of $L=1$. We suggest that the resonances are the members of the isobaric triplet of the ${}^{3}P$ resonances in $A=6$ nuclei.

• Received 28 January 2005

DOI:https://doi.org/10.1103/PhysRevC.71.064316