A Determination ofemby Means of Photoelectrons Excited by X-Rays

A value of $\frac{e}{m}$ has been obtained by a magnetic deflection method by making use of x-ray photoelectrons and the magnetic spectrograph. Electrons were ejected from thin evaporated or sputtered films of gold, silver, copper and platinum by the x-radiation from a molybdenum target metal tube placed close to the film and working at an input of 1.5 kilowatts. The velocity of ejection of the photoelectrons was computed from the difference between the energies associated with Mo $K$ radiation and the various absorption limits of the metal films. Relativity corrections were made since these velocities correspond to from 8000 to 15,000 equivalent volts. The ${\alpha }_1$ and ${\alpha }_2$ components of the molybdenum $K\alpha$ line were clearly resolved since the magnetic field was kept very constant by the use of a potentiometer and continuous hand control. The weighted mean value of $\frac{e}{m_0}$ obtained from five plates is 1.7570±0.0026×${10}^7$ e.m.u. per gram. This result is based upon a value of $\frac{h}{e}=1.3737\mathrm{}\pm 0.0005\times {10}^{-17\mathrm{}}$ as taken from x-ray crystal measurements. By taking $\frac{h}{e}$ from x-ray data the resulting value of $\frac{e}{m}$ is independent of the uncertainty involved in the crystal grating constant.