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

Neutron deexcitation mechanism through pre-equilibrium and equilibrium phases of the ${}_{}{}^{164}{}_{}{}^{}\mathrm{Dy}$($\alpha$,$\mathrm{xn}\gamma$) reaction at $E\left(\alpha \right)=120\mathrm{}$ 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 (∼1.7), pre-equilibrium quasitemperature (∼6 MeV), the average exciton particles number around 20, and the equilibrium temperature (1.6 MeV).