The yield of secondary electrons ${\gamma }_n$, from cleaned surfaces of polycrystalline molybdenum has been measured for argon neutral atoms (${\mathrm{Ar}}^0$) in the energy range 500-2500 eV. The values of ${\gamma }_n$ thus obtained are compared with ${\gamma }_i$, the yield for argon ions previously determined. It is found that the rates of increase of ${\gamma }_i$ and ${\gamma }_n$ with energy $E$ are not equal in the region of kinetic ejection. The ratio $\frac{\left(\frac{d{\gamma }_i}{\mathrm{dE}}\right)}{\left(\frac{d{\gamma }_n}{\mathrm{dE}}\right)}$ is 1.5. The result indicates that assumed models concerning the respective contributions of potential and kinetic ejection to the secondary electron yield at energies above 1000 eV should be modified.

• Received 29 October 1962

DOI:https://doi.org/10.1103/PhysRev.129.2086