1.6 The e- correlation in ⁸Li decay

E.G. Adelberger, A. Cronin, L. De Braeckeleer, G.B. Franklin,^* H.E. Swanson, K.B. Swartz and Z. Zhao

The e- correlation in ⁸Li decay can be used to determine the induced tensor contribution to the decay. We made preliminary attempts to measure this correlation by detecting, in coincidence, the two 's from the decay of the ⁸Be daughter state. We used the target transfer system of the 'mass 8' apparatus at the UW tandem accelerator. The energies E₁ and E₂ of the two 's were registered in pairs of thin surface-barrier detectors. These counters were backed by large surface-barrier VETO counters to identify events where the counter was struck by both the and one of the 's from a given decay. The sum energy, =E₁ + E₂, of an event gave the excitation energy of the daughter state, while the difference energy =E₁ - E₂ (which ranges up to ±400 keV) was sensitive to the lepton recoil (and therefore to the e- correlation). The energy response of the surface-barrier detectors was measured on-line using an E = 3183keV ¹⁴⁸Gd source and (at a variety of energies) in subsequent runs using elastically scattered 's from the UW tandem accelerator. These preliminary measurements proved the usefulness of the technique. However, we did not obtain a final result because of problems with gain drifts and with a coincidence efficiency of only 99%. We intend to cure these problems in future runs.