NUCLEAR PICKUP REACTIONS AND STUDIES OF He-ION INDUCED REACTIONS IN LIGHT AND MEDIUM WEIGHT NUCLEI

A study was made of nuclear pickup reactions and also direct reactions induced by protons, deuterons, and He-ion projectiles in which the exit channels may be reaehed through single or multi-nucleon pickup reactions. A simple theory leading to the differential form factors for the various reactions is presented. The theory is shown to give fairly accurate angular distributions when compared vvith recent measurements of (p,d), (d,t), and (d, alpha ) angular spectra. Total cross section measurements and mechanism studies of the ( alpha ,Be/sup 7/) reaction in the light elements (Al, Mg, Ti, Co, and Cu) were made. The cross sections at 40 Mev He-ion bombarding energy are shown to dccrease rapidly with increasing atomic number of the target nuclei. The excitation function data were compared with the predictions of the statistical theory of nucleair reactions for the Al/sup 27/( alpha ,Be/sup 7/)Na/sup 24/ reaction. Yields of both Be/sup 7/ and Na/sup 24/ were measured and discussed in terms of other possible mechanisms leading to the residual Na/sup 24/ nucleus (the Al/sup 27/( alpha , alpha He/sup 3 reaction). Bulk laboratory angular distribution measurements of the emerging Be/sup 7/ nuclei and more detailed angular spectra work showed the reaction tomore » proceed by a direct interaction mechanism in less than about 40% of the total yield in the 41 Mev He-ion bombardment of aluminum, the principal mechanism in the A1/sup 27/( alpha ,Be/sup 7/) reaction being the evaporation of the heavy particle from a highly excited compound nucleus. A study of the Al/sup 27/( alpha ,3p)Mg/sup 28/ and t of aluminum and magnesium targets with 42 Mev He-ions was made, and excitation functions from reaction threshold to 40 Mev are given. An investigation of numerous other He-ion induced reactions, particularly ( alpha , alpha n) reactions in cobalt, nickel, and silver isotopes was carried out and the results discussed in terms of the various possible mechanisms for the reactions. Excitation functions are given for the production of Na/sup 22/ from the bombardment of aluminum with 30-42 Mev He-ions, which proceeds chiefly through the reaction Al/sup 27/ ( alpha ,2 alpha n)Na/sup 22/, and of Na/sup 24/ from the bombar dment of natural magnesium, primarily through the s of the Ni/sup 62/ ( alpha ,n)Zn/sup 65/ + Ni/sup 61/( alpha ,)Zn/sup 65/, Ni/sup 58/( alpha , alpha pn), Co/sup 59/( alpha ,2pn), and Ag/sup 107/( alpha , alpha 2n) reactions are presented and discussed.« less