Elastic Scattering of Nitrogen by Carbon

Abstract

The differential cross section for the elastic scattering of nitrogen from thin carbon foils was measured from about 40 to about 140 deg in the center-of-mass system. The measurements were made at three energies: 27.3 Mev, 23.5 Mev, and 21.5 Mev, mean energy in the 1-Mev thick targets. The angular resolution was about 1 deg. Scattered nitrogen and recoil carbon atoms were counted in coincidence. Positions of the two counters, as prescribed by the kinematics of elastic scattering, served to discriminate against inelastic events and transfer reactions. The differential cross sections at all three energies exhibit marked structure especially beyond 90 deg. An optical model scattering calculation using a Saxon potential with $V=45\mathrm{}$ Mev, $W=6\mathrm{}$ Mev, and $a=0.65\mathrm{}$ fermi was performed. The results of the calculation exhibit fair agreement with the data. The results of the experiment are also compared with the predictions of a sharp cutoff model for elastic scattering and show no agreement with the theory. Analyzing the data in terms of a diffraction model the positions of the well-defined minima yield an interaction distance $R$ such that $r_0=1.18\mathrm{}\pm 0.02$ in the relation $R=r_0({A_1}^{\frac{1}{3}}+{A_2}^{\frac{1}{3}})$.