Angular distributions for C12(p)N15 at 16.1-19.0 Mev and F19(p)Ne22 at 18.9 Mev

Abstract

Angular distributions have been measured for the reactions C12(p)N15 and F19(p)Ne22 using the cyclotron 19-Mev alpha-particle beam. The C12(p0)N15 data at 18.0, 17.1, and 16.1 Mev differ markedly from the 19.0-, 18.7-, and 18.3-Mev data; the latter three are very similar to each other. The differential excitation function at 31.8°(lab) shows a resonance at 17.5 Mev with a width at half-maximum of 2 Mev. Steep backward peaking is observed in the 16.1-Mev data. Some of the features of the 17.1- and 18.0-Mev data can be represented by Butler's formula for (p) reactions using l=1 and r0=5.9 and 5.5f, respectively. For the F19(p)Ne22 data the cross sections for the transition to the ground state of Ne22 are factors of 10 to 20 less than the cross sections for the transition to the first excited state of Ne22. This inhibition, together with the F19(n, d)O18 data, may be explained by assuming that the two last neutrons of F19 are not disturbed in the direct interactions and that they are in a (d522)0 configuration in Ne22, in a (d522)2, or (s122)0 configuration in F19. Using r0=5.1f, Butler's formula accounts reasonably well for the forward peak and the location of the minima of all three angular distributions for the region of angles less than 90°. The angular distributions are all peaked in the backward angles. © 1960 The American Physical Society.