Complementary applications of the practice of measurement of the specific electronic charge

Abstract

In the usual experiment of the measurement of the e/m ratio, an electron beam is fired into an ampoule containing helium at low pressure, immersed in a magnetic field that confines the beam in a circular path. From the measurement of the radius of this path and other parameters, the e/m ratio is calculated. In the present work, a method is proposed to calculate the initial current of the electron beam. On the other hand, from digital photographs, the change of the absolute luminous intensity of this beam is estimated. Then these data are adjusted with a theoretical model of the dynamics of the same, from which the effective section of electron-He interaction is obtained. The objective is didactic, and aims to quantitatively justify initial assumptions of the usual practice, and to give an introduction to the interaction of a beam of particles with a neutral gas by means of the Invariant Imbedding formalism.