R. A. Kaye

First observation of a strongly-coupled band in even-even A ≈ 80 nuclei: 76Kr

Abstract A new ΔI = 1 band has been discovered in 76Kr, the first to be observed in an even-even A ≈ 80 nucleus. The rotational band is built upon a Kπ = 4(+) state at 2844 keV excitation energy which is interpreted as a strongly-coupled two-quasineutron configuration ( [301] 3 2 − ⊗ [303] 5 2 − )4+ at a prolate deformation of π2 ≈ 0.34.

Angle-corrected doppler-shift attenuation analysis

If all nuclei from a reaction recoil from a thin target at essentially the same velocity, it is easy to correct for the variation of γ-ray energy with emission angle due to the Doppler shift to combine data from different detectors and improve the statistical accuracy. However, the situation is more complex with thick-target experiments in which γ emission occurs over a wide range of velocities. Now charged-particle detector arrays allow the determination of the exact recoil angle and velocity from fusion-evaporation reactions on an event-by-event basis. Corrections for the variations in the Doppler shift due to different angles between each detector and each recoil event and for the variations in the recoil velocities would provide better statistical accuracy and more accurate line shapes for analysis using the Doppler-shift attenuation method to infer mean lifetimes of excited states. A technique to make these corrections has been developed using simulated line shapes.

Nuclear structure of neutron-rich 78 As

Excited states in the neutron-rich doubly-odd nucleus78As have been identified for the first time by proton-γ and γ-γ coincidence measurements via the76Ge(α, pn) reaction at 32, 36, and 40 MeV beam energy. Four levels have been found to decay with lifetimes in the nanosecond region. The 5(+) to (10+) states are ascribed to the (πg9/2⊗νg9/2) intruder two-quasiparticle configuration with some collective components in the 9(+) and (10+) states.