Measurements were made of the energy spectra at various angles of protons and a. particles emitted from the reactions of protons with Ni 62 and a. particles with Co 59 to determine the extent to which the deexcitation of the reaction intermediate, Cu 63 at 20.2-MeV excitation energy, is independent of its mode of formation. Similarly, the reaction intermediate Ni 60 at 23.6 MeV was formed by protons on Co 59 and a. particles on Fe 56 , again to determine to what degree its deexcitation by proton and a-particle emission is independent of its mode of formation. Small differences in the shapes of corresponding energy spectra {_{p, p') versus (a, p), and (a, a.') versus (p, a) ] that were observed in apparent violation of the Bohr-independence hypothesis are removed after account has been taken of the effects of angular-momentum conservation. The observed enhancement of the ratio of cross sections a(x } p)/cr{x ) a) for the proton entrance channel over that for the a entrance channel cannot be interpreted in terms of angular-momentum conservation. The consequences of the possibility of isotopic-spin conservation, when considered, lead to enhanced proton reemission similar to that observed experimentally.
Cross sections and excitation functions have been determined for spallation and fiss-ion products from bombardments of Th 232 with helium ions (15 to 46 Mev) and u 2 33 with deuterons (9 to 24 Mev). This work extends a series of investigations of charged particle (a, d, and p) induced reactions in heavy elements (z ~ 88). Radiochemical methods were employed to isolate products corresponding to the following spallation reactions: neutron emis-, sion, (a,4n), (a,5n), (d,n), (d,2n), and (d,3n); emissionof one proton and neutrons (a,p), (a,pn), (a,p2n), and (a,p3n); and emi~sion of two protons and neutrons, (a,2p), (a,2pn), and (a,an), and (d,an). In addition, the following fission products were isolated from one or more bombardments: zn7 2 , The results show that fission is the predbminant reaction at all energies for Th 2 3 2 and to an even greater extent for u 2 33. The data for the surviving spallation products are consistent with several mechanisms of reaction, including compound-nucleus formation and evaporation, direct interactions between nucleons of the incoming helium ion or deuteron and nucleons of the nucleus, and a combination of these types of processes (direct interaction followed by evaporation). In general, the results confirm and extend previously established concepts. The fission mass-yield curves are similar to those found for other heavy target isotopes (~or elements from thorium to plutonium). The minimum in the curves in the region of mass 120 tends to disappear as helium-ion or deuteron energy is increased.The (a,pxn), (a,2pxn), (a,an), (d,n), and (d,an) products are attributed to direct interactions, with complex particles emitted in preference to a series of protons and neutrons. Thus (a,d), (a,t), and (a,tn) mechanisms would account for most of the (a,pn), (a,p2n), and (a,p3n) products, respec-In the case of the (a,t) and (a,tn) reactions, analysis of the ratio leads one to the conclusion that with 35-Mev helium ions only 9% of outgoing tritons leave the residual nucleus with sufficient energy to evaporate a neutron or undergo fission, and with 44-Mev helium ions only 20% do so. The (d,n) product probably results from the stripping reaction.
The transtkrall.i_um region i s u n i q u e Ir, t h a t t h e general occw-rence of alpha decay ~L~! T S one t o construct d o s e e dezay-energy cycles contain5 ng two aip*Qa-decay energies and two beta-aeeay energies. As an example, t h e cycle 3
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