In the precise measurement of the critical potentials of gases

Abstract

The aim of this research has been to attempt to increase the accuracy with which the measurement of the critical potentials of gases can be made, and so being about a closer confirmation of the numerical relationships of the quantum eory. We must first examine the factors which have limited the accuracy previous measurements, and then see by what means we may increase the decision of these determinations. In all methods in common use the critical potentials are determined from singular points in the current-voltage curves of the apparatus. These points the case of the Lenard and allied methods are upward bends or “kinks,” while in the inelastic impact method of Franck and Hertz they are downward ends, that is to say, they are maxima. Were these changes ideally abrupt here would be no difficulty in fixing the critical points with great accuracy if we ignore for the moment the question of the correction for the initial velocity of emission of the electrons and for contact potential differences); and so in conjunction with the spectroscopic evidence we could obtain independent determinations of the Planck constant h .