Angular distributions of the neutron polarization for the BBe(~, no) C and Be(~,n&) C (4.43-MeV) reactions have been measured at six projectile energies in the 4.5to 5.85-MeV interval. Large polarizations are observed for both neutron groups over the whole energy range, making both groups useful sources of polarized neutrons. The ground-state neutronpolarization angular distributions have been analyzed simultaneously with the recent crosssection data of Obst etal. using an S-matrix search code to make J~a ssignments to states in SC in the 13to 15-MeV excitation energy range. The combined data set can be adequately described over the whole energy range by assuming the presence of at least five broad states. The J assignments and the probable excitation energies for these states are given. I. INIODUCTIONThis paper reports observations and analyses of neutron polarizations in the 'Be(n, n) "C reaction for the 4to 6-MeV n-energy interval. The motivations for the experimental investigations were (1) to provide information of a new kind in this energy interval relating to the reaction mechanism, (2) to utilize these data along with published cross-section data to obtain spectroscopic information, and (3) to determine if this reaction is a useful source of higher-energy polarized neutrons.Previous investigations of this reaction employing several experimental techniques have resulted in conflicting interpretations of the reaction mechanism involved, ranging from a purely compoundnucleus picture to one where a pure direct reaction including a heavy-particle-stripping process is advocated. I ietz et gl. ' discuss most of the relevant work on this point. It is clear however that the compound-nucleus mode is important as the cross-section excitation curves exhibit pronounced fluctuations up to F."=12 MeV. Much of our knowledge of states in the "C compound system for E")11 MeV has been obtained from these (n, n) investigations. However, the observed structure is generally broad with an occasional sharp peak superimposed on this, and it is likely that more than one level contributes to the individual fluctuations. " An analysis of reaction cross-section data alone would be difficult, and probably inconclusive; in fact, there are very few attempts reported in the literature. As might be expected, our knowledge of the "C level structure in the 10-20-MeV excitation range is largely unknown.It is in situations such as this that supplementary experimental information such as provided by polarization investigations can be of considerable value. For instance, the measurement of complete polarization angular distributions over a broad energy interval can aid in establishing the reaction mechanism. An analysis of o(8) and P(9) data simultaneously can provide useful spectroscopic information, as shown by Darden' and Baker et al. ' In the present work the ground-state neutron-polarization data provide evidence supporting the dominance of a compound-nucleus mechanism. Accordingly our P(8) data have been analyzed together with published v...
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