Isomer-scope: A new instrument for in-beam γ-ray spectroscopy through deep inelastic collisions

Abstract

A new instrument, isomer-scope, has been constructed to observe the ns-μs isomers produced by deep inelastic collisions. It consists of a Si detector, a γ-absorber and Ge detectors. The Si detector provides the energy and timing signals of projectile-like fragments(PLF) for the coincidence measurement and also stores the isomers of PLF for the Ge detectors. The γ-absorber shields the Ge detectors from the strong γ-radiation generated in the target. Thus, the isomer-scope greatly intensifies the γ-rays from the isomers of PLF in the PLF-γ(-γ) coincidences. In the reaction 635 MeV 76Ge + 198Pt , a new isomer of 69Cu was found to be excited at 2741 keV. It decayed with T 1 2 = 0.36(3) μ s via transition cascade 190-680-1871 and via cascade 73-486-471-1711. The cascade 486-471-1711 was fed in part from another state; either the 486 keV γ-ray or a side-feeding γ-ray unobserved was an isomeric transition of T 1 2 = 25(5) ns .