Spectroscopy Of A=9 Hyperlithium With The (E, E ' K+) Reaction

Missing mass spectroscopy with the (e, e', K+) reaction was performed at Jefferson Laboratory's Hall C for the neutron-rich Lambda hypernucleus Li-9(Lambda). The ground-state (g.s.) energy was obtained to be B-Lambda(g.s.) = 8.84 +/- 0.17(stat.) +/- 0.15(sys.) MeV by using shell-model calculations of a cross-section ratio and an energy separation of the spin doublet states (3/2(1)(+) and 5/2(1)(+)). In addition, peaks that are considered to be states of [Li-8(3(+)) circle plus s(Lambda) = 3/2(2)(+), 1/2(+)] and [Li-8(3(+)) circle times s (Lambda) = 5/2(2)(+), 7/2(+)] were observed at E-Lambda (no. 2) = 1.74 +/- 0.27(stat.) +/- 0.11(sys). and E Lambda (no. 3) = 3.30 +/- 0.24(stat.) +/- 0.11(sys.) MeV, respectively. The E Lambda (no. 3) is larger than shell-model predictions by a few hundred keV, and the difference would indicate that a He-5 + t structure is more developed for the 3(+) state than those for the 2(+) and 1(+) states in a core nucleus Li-8 as a cluster model calculation suggests.