New techniques for determining spins and parities of neutron resonances and their impact on nuclear astrophysics

We describe new techniques for determining spins and parities of neutron resonances which have resulted in large improvements over previous methods. These advances have made it possible, for the first time, to obtain reduced-neutron- and total-radiation-width distributions separately for resonances of different spin and parity in odd-A target nuclides. Using these new as well as previous data, we show that neutron distributions sometimes are significantly different from the Porter-Thomas distribution assumed by the nuclear statistical model. Furthermore, we show that the radiation-width distributions often are substantially different than predicted by the nuclear statistical model using standard level densities and photon strength functions. These differences could have significant impact on astrophysical reaction rates calculated using the statistical model.