The polarization of protons elastically scattered from alpha particles was observed by measuring the asymmetry obtained by doubly scattering protons in helium. Protons from the Brookhaven National Laboratory Van de Graaff generator entered a helium-filled double-scattering chamber through a 50-microinch nickel window. The first scattering was at either 104° 29′ (c.m.) or 73° 38′ (c.m.) and the second scattering was to left and right at 73° 38′ (c.m.). The doubly scattered protons were detected by 50-μ Ilford C-2 plates. The polarization product, $P_a{P}_b$, was calculated from the left-right ratio ($R$) using the formula $R=\frac{(1+P_a{P}_b)}{(1-P_a{P}_b)}$, where $P_a$ and $P_b$ are the polarizations at the first and second scatterings, respectively. Three interdependent measurements, in which $P_a{P}_b$ was equal to $P_1{P}_2$, $P_1{P}_3$, or $P_2{P}_3$, yielded values for $P_1[3.580\mathrm{} \mathrm{Mev}, 104° {29}^{\prime } (\mathrm{c}.\mathrm{m}.\mathrm{}\left)\right]$, $P_2[2.020\mathrm{} \mathrm{Mev}, 73° {38}^{\prime } (\mathrm{c}.\mathrm{m}.\mathrm{}\left)\right]$, and $P_3[1.375\mathrm{} \mathrm{Mev}, 73° {38}^{\prime } (\mathrm{c}.\mathrm{m}.\mathrm{}\left)\right]$. The calculated polarizations are in the direction of the normal n (n=${\mathrm{k}}_0$×k|${\mathrm{k}}_0$×k|) to the scattering plane. The following results were obtained:

• Received 24 February 1958

DOI:https://doi.org/10.1103/PhysRev.110.1398