4 MeV in Fig. 3 is underestimated. As long as the true ratio of the intensities of these components is unknown, it is difficult to say whether the results for the $\gamma$-radiation of Li obtained by one method or another coincide or do not coincide. One can only assert that there is no gross contradiction in these data.

Assuming that the initial energy distribution for electrons and positrons is the same, and taking into account the different thicknesses of the effective layers for paired and single electrons, the authors find that in $1\ \mathrm{cm}^3$ of lead 1.8 pairs are produced per 1 single electron for a $\gamma$ quantum of energy 5.4 MeV, and 10 pairs per 1 electron for 12 MeV. These data are in good agreement with Oppenheimer’s theory.

The stated results show what an important role pair production, which until quite recently had escaped observation, plays in the process of absorption of high-energy $\gamma$ quanta.

L. Gorshev.

ARE METAL ATOMS DEFORMED DURING COLD WORKING

A number of authors (Fann-Lim, Tammann) have expressed the opinion that, after plastic deformation, metal atoms are in a special state and have a charge distribution different from the normal one. The latter can be determined by directly measuring the intensity of x-rays reflected from a crystal face. Taking into account the dependence of the intensity of the reflected x-rays on various factors (the distribution of atoms—the structural factor, thermal motion—the Debye factor, etc.), among them we also find a factor due to the charge distribution within the atom, the atomic factor $F$:

$$ F = Z \int_{d/2}^{d} p(z)\cos \frac{4\pi z \sin \vartheta}{\lambda}\, dz, $$

where $p(z)$ is the distribution of charge density between neighboring atomic planes of the reflecting crystal face. The defined integral is a function of $\vartheta$. When $p(z)$ changes, the angular dependence of $F$ also changes.

J. Boyd attempts, by measuring the atomic factor for deformed (powder) and undeformed Be, to resolve the question of the deformation of Be atoms. The latter was chosen because of the small total number of electrons in it, so that the influence of the outer electron here should be rather appreciable. The results lead the author to the opinion that the atomic factor does not change as a result of the work-hardening of the metal. Attention is drawn, however, to the fact that the factor of lattice disorder due to deformation, which should act analogously to temperature, was not taken into account. Nevertheless, the work is of interest as an attempt to solve a question that is very important for the theory of plastic deformation (James E. Boyd, Scattering of X-Rays by cold worked and annealed Berillium. Phys. Rev., 45, 832, 1934).

S. Konobeevsky