Elastic Scattering of Heavy Ions from Several Gas Targets

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The absolute differential cross section for the elastic scattering of oxygen by gaseous targets of helium, nitrogen, and neon and of carbon by nitrogen were measured from about 4 to \ensuremath{\sim}20 degrees in the center-of-mass system. The energy of the incident heavy ions was \ensuremath{\sim}10 Mev per atomic mass unit. The ratio of the elastic cross section to the Coulomb cross section exhibits diffraction-like oscillations which damp out as $\ensuremath{\eta}=\frac{{Z}_{1}{Z}_{2}{e}^{2}}{\ensuremath{\hbar}v}$ increases from \ensuremath{\sim}1 to \ensuremath{\sim}4. The results are compared with the predictions of a simple diffraction model, a sharp-cutoff model, and a modified-cutoff model. Reasonably good agreement is obtained in predicting the angular position of the maxima and minima, but not the absolute cross section. The modified-cutoff model appears to apply only if $\ensuremath{\eta}$ is greater than about 2.5. The value of ${r}_{0}$ found for the ${\mathrm{O}}^{16}$-Ne scattering is 25% greater than for the remaining three reactions.