Cascade Gamma Decay In The Li-7(Lambda) Hypernucleus

In a gamma-ray spectroscopy experiment with the (K-, pi(-)) reaction on a B-10 target, we have observed the 7/2(+)-> 5/2(+) spin-flip M1 transition in Li-7(Lambda) via gamma-gamma coincidence with the 5/2(+)-> 1/2(+)E2 transition. This is the first successful gamma-gamma coincidence measurement for hypernuclei. The measured M1 gamma-ray energy is 470.8 +/- 1.9(stat)+/- 0.6(syst) keV. The spacing of the 7/2(+), 5/2(+) doublet is consistently explained using the strengths of the spin-spin, Lambda-spin-orbit, and tensor interactions obtained from previous gamma-spectroscopy experiments.