The Radio-activity of the Chemical Elements

Abstract

IN connection with the emission, from the radio-active elements, of corpuscles with velocities below the critical velocity necessary for the ionisation of gases, it has occurred to me that such a form of radiation is possibly a fairly general property of the chemical elements. It is, I think, usually accepted that “γ” radiation always accompanies the projection of “β” particles, and the extreme penetration of the “γ” rays seems to be directly due to the very high velocity of the average “β” particle. As the efficiency of the “X” rays is due to the sudden negative acceleration of the unit electrical charges (i.e. the corpuscles) as they strike the anti-kathode, it appears quite possible that corpuscles, moving with comparatively low velocities, may yet be capable of causing a form of “γ” radiation of feeble penetrating power. The fact that the kathode stream, which can hardly penetrate the glass of the tube, is still able to set up very penetrating X radiation when given a sudden negative acceleration by impact with the platinum anti-kathode may perhaps be given as an instance in support of this idea. It seems probable that the photographic action of a beam of corpuscles (deviated away from the “γ” radiation by a magnetic field) may be chiefly due to a form of “γ” ray set up on contact with the plate itself. The several mysterious instances of the fogging of photographic plates left in certain conditions for considerable periods may be caused by a very feeble form of “γ” radiation set up by the impact of slow-moving corpuscles on the surrounding matter. Such evidence of these slow-moving corpuscles may be somewhat meagre and doubtful, but I think that, so far as the ordinary chemical elements are concerned, the emission of such corpuscles may be very much greater than the measured activities would lead us to suppose.