A tube especially designed for the study of the Compton effect at large angles of scattering.—The structure of the Compton line obtained with this tube for a scattering angle of nearly 180° with a metallic beryllium scatterer is shown.

Interpretation of the structure of the Compton line.—The diffuse structure of the Compton line is here attributed to a broadening caused by the velocity distribution of the scattering electrons in the solid scatterer analagous to a Doppler broadening and a relation between line structure and velocity distribution is derived. The observed line structure from the beryllium scatterer is compared with theoretical structures computed on several alternative assumptions as to electron velocity distribution. It is assumed: —1. That electrons in the solid scattering substance have the velocity distribution required by a wave-mechanical atom model for a free atom of that substance far removed from neighbors. 2. That electrons may be divided into two classes, one class the metallic or conductive electrons in the state of a degenerate electron gas subject to the Pauli Exclusion Principle and having the velocity distribution derived by Sommerfeld, and the other class as in the 1st assumption unperturbed by the neighboring atoms. 3. That electrons may be divided into two classes as before but that those forming an electron gas have the classical velocity distribution required by the Maxwell-Boltzmann equipartition law. 4. That electrons have the velocity distribution required by the older Bohr-Sommerfeld atom model with point electrons executing Kepler orbits and as in the first assumption unperturbed by neighboring atoms.

The distribution of electron velocities in metals.—The results strongly contradict the classical distribution of electron velocities in solid bodies predicted by the rigid interpretation of the Maxwell-Boltzmann equipartition principle. They are also in contradiction with the older Bohr-Sommerfeld atom model. The results are in accord with the wave-mechanical atom model and constitute favorable evidence for the Sommerfeld distribution of metallic electron velocities and for the degenerate gas state.

• Received 10 February 1929

DOI:https://doi.org/10.1103/PhysRev.33.643