Compton Scattering of 2.62-Mev Gamma Rays by Polarized Electrons

Abstract

The differential cross section for Compton scattering of a circularly polarized photon by an electron with given initial spin orientation can be written as a sum of the common Klein-Nishina formula for no polarization and a term sensitive to polarization. The total cross section is $\ensuremath{\sigma}={\ensuremath{\sigma}}_{0}\ifmmode\pm\else\textpm\fi{}{\ensuremath{\sigma}}_{1}$. A measurement of the transmission of 2.62-Mev gamma rays through iron magnetized along the transmission direction relative to that through unmagnetized iron gives the absolute value of ${\ensuremath{\sigma}}_{1}$ for this energy, if the number ${\ensuremath{\nu}}_{s}$ of polarized electrons per iron atom at saturation is known. For ${\ensuremath{\nu}}_{s}=2.06$, $\frac{{\ensuremath{\sigma}}_{1}}{\ensuremath{\pi}{{r}_{0}}^{2}}=0.089\ifmmode\pm\else\textpm\fi{}0.007$. This agrees with the theoretical value 0.093. Alternatively, the theoretical ${\ensuremath{\sigma}}_{1}$ and the measurements would yield ${\ensuremath{\nu}}_{s}=1.97\ifmmode\pm\else\textpm\fi{}0.15$.The application of the method of this experiment to measurement of gyromagnetic ratios for ferromagnets is suggested, as is its application to the analysis of circularly polarized radiation.