Measurements on thevcDependence of the Beta-Circularly Polarized Gamma Correlation inCo60Using a Magnetic-Lens Spectrometer

Measurements have been made of the circular polarization of ${\mathrm{Co}}^{60}$ gamma rays in coincidence with beta rays whose momentum is defined by a magnetic lens spectrometer. The gamma rays are analyzed by a transmission-type Compton analyzer of new construction (toroidal geometry). At nominal 180° between beta and gamma, and accepting both of the gamma-ray lines, the degree of circular polarization is generally higher than the expected $+\frac{0.33v}{c}$ and markedly so for the smaller speeds. Proceeding downward in $\frac{v}{c}$ from 0.71 to 0.33 there is no indication that the polarization falls off as fast as would be given by a "$\frac{v}{c}$ law."