The use of fast polarized projectiles in nuclear reactions provides a possible tool for studying the spin-dependence of nuclear interactions. In the first section general properties of such reactions are discussed. For incident neutrons or protons and a value $n,p$ for the maximum partial wave that need be considered in the incident beam, the results are summarized in theorems 3 and 4.

The following reactions involving polarized protons are shown to be possible: (a) production of polarized protons by the ($n,p$) reactions of N or ${\mathrm{He}}^3$ using polarized thermal neutrons, (b) detection of polarization by means of the ${\mathrm{Li}}^7(p,\alpha )\alpha$-reaction, and (c) production or detection by the resonance scattering of protons from helium. Considering these reactions alone and exploring the fundamental limitations on intensity, one finds that the intensity problem appears to be least critical if (c) is used for both production and detection. The polarization effect usually depends on at least one parameter which does not affect or affects much less critically the unpolarized result. The polarization effect caused by the spin-dependent Coulomb scattering is calculated and found to be less than 5 percent for atomic number $Z$ less than 5, except for special cases. Protons retain their polarization while being slowed down.

• Received 17 January 1949

DOI:https://doi.org/10.1103/PhysRev.75.1664