Neutron spectra and angular distributions from the reactions /sup 181/Ta(p,n)/sup 181/W and /sup 181/Ta(n,n')/sup 181/Ta

Spectra and angular distributions have been measured for neutrons from the reactions /sup 181/Ta(n,n')/sup 181/Ta at initial neutron energy 9.1 +- 0.2 MeV and /sup 181/Ta(p,n)/sup 181/W for E/sub p/=10.2 +- 0.2 MeV. The neutron spectra were measured by the time-of-flight method in the 150-cm cyclotron at our Institute at angles 30, 60, 90, 120, and 150/sup 0/. It is shown that for identical excitation energy of the nuclei the integrated spectrum of inelastically scattered neutrons has a more energetic form than the neutron spectrum from the (p,n) reaction, and an analysis of the spectra carried out in terms of the model of pre-equilibrium nuclear decay showed that the difference in the fraction of nonequilibrium processes is significantly greater than predicted by the model. The angular distribution of inelastically scattered neutrons has a strong asymmetry in the high energy part, while in the (p,n) reaction it is symmetric within experimental error about 90/sup 0/. This apparently indicates that direct processes whose contribution to the spectrum in the (p,n) reaction is substantially smaller are responsible for the high-energy portion of the spectrum.