TABLE III-E STOPPING POWERS OF ATOMS FOR THE ALPHA-PARTICLES OF RaC' (84RaII) RELATIVE TO THAT OF THE OXYGEN ATOM TABLE III-F STOPPING POWERS OF MOLECULES FOR THE ALPHA-PARTICLES OF RaC' (84RaII) RELATIVE TO THAT OF THE OXYGEN ATOM RELATIVE TOTAL IONIZATION BY ALPHA-RAYS IN VARIOUS GASES IV. BETA-RAYS 1. NATURE OF BETA-RAYS The term ẞ-rays was applied by Rutherford to the negatively charged rays emitted by radioactive substances. Experiments on electrostatic and magnetic deflections of B-rays, particularly those of Kaufmann and Bucherer, leave no doubt that the B-particle is an electron of the same nature as any other electron. No experiment, however, sufficiently accurate to prove directly that the charge is constant or that the variation of e/m with velocity agrees exactly with the Lorentz-Einstein formula, has been performed. The experiment of Kovarik, who checked the number of B-particles (counted by the point-discharge method), by dividing their total charge by the electronic charge, had an accuracy of only 1.5%, and is the only experiment bearing directly on the former point. The work of Soddy and Fajans shows that when a radio-element emits B-rays in disintegrating, the succeeding product is shifted one place, to the next higher atomic number, in the periodic table. This proves that in B-ray disintegration one emitted electron is of nuclear origin. On the other hand, the recent work on B-ray spectra and on their relation to y-ray spectra proves that some of the B-particles are of extra-nuclear origin. It seems proper to suggest that when the controversy about the origin of certain disputed B-rays is settled that a distinction in terminology be made between " nuclear" and "orbital" B-rays. The continuous curvature sometimes observed in B-ray tracks by C. T. R. Wilson's method has led A. H. Compton to suggest that the electron may have magnetic polarity. The calculations of Kapitza show, however, that electrons possessing sufficient magnetic moment to explain the apparent curvature would at atomic distances exert such great forces that ionization should occur where it is not experimentally observed. Glasson suggests that the curvature of the B-ray tracks is due to transient pseudocrystalline structures in the gas. Bothe denies that such continuous curvature really occurs. In this connection it may be noted that Nicholson pictures the electron as a state of strain in the ether, concentrated at a point and rapidly diminishing outward. He regards the electric charge as a fundamental property of the strain and is able on certain assumptions to calculate the effective radius of the electron. |