Untersuchung des Neutroneneinfang-Mechanismus in der Reaktion 80Se(n,γ)81Se und der Kernstruktur von 77Se, 78Se und 81Se mit Hilfe von (n,γ)-Reaktionen / Neutron Capture Mechanism in the Reaction 80Se(n,γ) 81Se and Nuclear Structure of 77Se, 78Se and 81Se, Studied In The (n,γ) -Reaction

Abstract

Abstract Gamma radiation from the capture of neutrons in natural Se and in enriched 76Se and 80Se has been studied with different Ge (Li)-detectors, with a Ge(Li)-NaJ pair spectrometer and with a Ge (Li) -Ge (Li) two-paramater γ-γ coincidence system. These measurements resulted in a considerable improvement of the level schemes of 77Se, 78Se and 81Se. The 81Se and the 107Ag level schemes are compared, and the applicability of phonon-particle coupling to low-lying states of 81Se is discussed. In the case of 77Se, some properties may be possibly better described by the Nilsson model. It is rather clear, however, that both models can only be regarded as limited approximations and that more refined models are required for Se nuclei. The well-known, unusually small isomeric cross section ratio of 81Se, and the weak population of p-single-quasiparticle states by primary transitions from the capture state 80Se + n, which shows up in our measurements, may be understood by assuming a capture state containing a doorway state with a simple collective excitation.