The γ Rays of Uranium

Abstract

OUR knowledge of the γ rays of uranium has until now been confined to their discovery by Rutherford (Phys. Zeit., 1902, 517) and to the observations of Eve (ibid., 1907, 185). The latter directed attention to their extraordinary feebleness and to their relatively low penetrating power. Eve found that uranium gives out only about one-tenth as much γ radiation as thorium when examined through 0.64 cm. lead, which is most remarkable, considering that it gives about six times more β radiation. Whereas the γ rays of thorium have the same value for the absorption coefficient as those of radium [λ(cm.)^-1=from 0.57 to 0.46 over a range of from 0.64 cm. to 3.0 cm. of lead], the uranium γ rays are far more easily absorbed. Eve gave the value 1.4 for λ for thicknesses of lead between 0.28 cm. and 0.92 cm. He stated that the radiation was homogeneous, that the absorption was exponential over this range, and that the rays were practically completely absorbed in 1 cm. of lead. He worked with uranyl nitrate.