The N__(a,a)N__ and N__(a,p)O_ß reactions for bombarding energies from 3 to 5 mev

Abstract

The purpose of this work is the investigation of the scattering and reaction resulting from the bombardment of N14 with alpha particles having energies from 3 to 5 Mev. The N14(a,p)O17 reaction is of some historical interest because it was the first of the laboratory induced nuclear reactions. The original experiments were performed in 1919 by Rutherford. Subsequent work on this reaction has been done by R. R. Roy using Polonium alpha particles and nuclear plates, by N. P. Heydenberg and G. M. Temmer, using artificially accelerated alpha particles with energies between 1.5 and 3.5 Mev, and others. The reaction and scattering cross sections give information about the positions and widths of energy levels of the compound nucleus F18 and an analysis of the data by the scattering matrix method as described by J. M. Blatt and L. C. Biedenharn may lead to assignments of total angular momentum and parity to the nuclear energy levels. When N14 is bombarded with alpha particles, reactions occur below 5 Mev. The first of these corresponds to elastic scattering of alpha particles, the second to a reaction with the protons going to the ground state of O17, and the third to a reaction with the protons going to the 0.875 Mev state of O17. We have not so far been able to observe this second proton group in our experiment; the yield of protons to the 0.875 Mev state is given by R. R. Roy, who used photographic plates, to be 0.12 of the yield to the ground state of O17. The analysis of the data is complicated by the large angular momentum of the ground of 017, (I = 5/2 +), because for a given value of the spin and parity of a level in the compound nucleus F18, there are many allowed values of 1p, the orbital angular momentum of the outgoing proton.