Differential cross sections for the elastic scattering of various hydrogen and helium isotopes have been measured using accelerated particles from the Los Alamos 42-inch cyclotron. The scattering of protons and deuterons from deuterons, tritons, and helium-three particles has been studied over an energy range of 5 to 14 Mev. The elastic scattering of ^10-Mev polarized protons has also been studied. In all cases nuclear emulsions were used as detectors.Proton-deuteron elastic scattering has been measured at 5.6 and 7.85 Mev. A comparison is made to results at nearby energies of both p-D and n-D scattering and to theoretical predictions. The scattering of 10-Mev polarized protons from deuterons has been measured and provides support for calculations using central force approximations.Measurements of p-T and />-He 3 elastic scattering at 6.5 and 8.34 Mev give angular distributions which are quite similar to those for p-D and p-Ke*. An encouraging agreement is found with resonating-group calculations with central-force approximations of the Serber type.Deuteron-deuteron scattering has been measured at 6.0, 8.2, 12.1, and 13.8 Mev. A preliminary theoretical treatment indicates that the process is predominantly hard-sphere scattering with no strong level splitting.Deuteron-triton and deuteron-helium three scattering has been measured over the energy range of 5 to 14 Mev.

Using the method of induced radioactivity we have measured the (n,2n) cross sections of C 12 , Cu 63 , and Mo 92 as a function of energy from threshold to 27 Mev. The positron activities of 20, 10, and 15.5 min, respectively, were employed. K-capture corrections were applied to the copper and molybdenum data. We have compared the copper and molybdenum data with the statistical theory of Weisskopf and collaborators and find satisfactory agreement from threshold to the onset of tertiary reactions.The reaction a-\-nucleus->/3+nucleons is considered where a and /3 are particles of quantized fields and the coupling to nucleons is assumed linear in the fields. By an extension of the recent work of Chew and Goldberger on potential scattering, the collision matrix has been manipulated into a term representing the impulse approximation plus three correction terms which are, respectively: The error in the impulse assumption arising from nuclear potentials; the "multiple scattering" which is at least fourth order in the coupling; and finally, a small term representing the effect of lowest order absorption. It is significant that there is no large term present, of the order of the impulse approximation term, which represents processes, second order in the coupling, where one nucleon absorbs a and another nucleon emits 0.

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