Nitrogen-Aluminium elastic scattering

Abstract

The differential cross section for elastic scattering of 27.3-MeV nitrogen ions from aluminium was measured from 36° to 134° in the centre-of-mass system. A coincidence system detecting both the nitrogen and the aluminium ions was used to identify the elastic events. The angular resolution was about ±1 degree. The ratio of the elastic cross section to the Coulomb cross section exhibits a small rise above unity near 50° (c.m.), then drops almost exponentially from 60° to 134° (c.m.), where it has a value of 0.0265. The results of the experiment are compared with the predictions of a sharp cutoff calculation. Reasonably good agreement is obtained from 36° to 96° (c.m.) with an interaction radius R = 9.07 × 10 −13 cm. If we define R = r 0( A 1 ⅓+( A 2 ⅓), the value of r 0 is 1.68 × 10 −13 cm. Beyond 96° (c.m.) the sharp cutoff calculation displays increasing oscillations and no longer fits the data. The results of a semi-classical scattering theory due to Ford and Wheeler are also compared with the experimental data. The best fit is obtained for a rainbow angle θ r = 94°, corresponding to r 0 = 1.59 × 10 −13 cm, and a surface thickness parameter ΔR = 0.83 × 10 −13 cm. Quite good agreement between this theory and experiment is obtained from about 94° to 134° (c.m.).