Pre-equilibrium neutron emission for theDy164(α,xnγ)Er168−xreaction studied byn−γcoincidence measurements

Abstract

Neutron deexcitation mechanism through pre-equilibrium and equilibrium phases of the $^{164}\mathrm{Dy}$($\ensuremath{\alpha}$,$\mathrm{xn}\ensuremath{\gamma}$) reaction at $E(\ensuremath{\alpha})=120$ MeV was studied as a function of the neutron multiplicity $x$. The deexciting neutrons with a wide range of the multiplicity $x$ showed energy and angular distributions characteristic of the pre-equilibrium process followed by equilibrium evaporation. The pre-equilibrium neutrons were found to carry away considerable amounts of angular momenta. The energy and angular distributions of the emitted neutrons were analyzed in terms of a simple two phase deexcitation model of the pre-equilibrium phase and the equilibrium phase. It gives the mean number of pre-equilibrium neutrons (\ensuremath{\sim}1.7), pre-equilibrium quasitemperature (\ensuremath{\sim}6 MeV), the average exciton particles number around 20, and the equilibrium temperature (1.6 MeV).NUCLEAR REACTIONS $^{164}\mathrm{Dy}(\ensuremath{\alpha},xn\ensuremath{\gamma})^{168\ensuremath{-}x}\mathrm{Er}$, $x=6\ensuremath{-}11$, $E(\ensuremath{\alpha})=120$ MeV; measured $\ensuremath{\sigma}(x)$, $\ensuremath{\sigma}({E}_{n},{\ensuremath{\theta}}_{n})$; deduced angular momentum removal by neutrons, pre-equilibrium effects, properties of pre-equilibrium phase. Two phase deexcitation model analysis. Enriched target.