The Scattering of Hydrogen and Helium Beams in Mercury Vapor

The scattering of beams of hydrogen molecules and helium atoms in mercury vapor has been investigated in the angular region from 5^ to 65^ at beam temperatures of 115^, 300^ and 590^. The results are expressed in terms of the number of molecules scattered per incident molecule, per cm path, per 10^-3 mm of mercury at 0^ per unit solid angle in the direction to the original beam. The general shape, the absolute intensity and the change in shape of the helium scattering curves with change in beam temperature is in moderately good quantitative agreement with the quantum theory of scattering of rigid spheres as developed by Massey and Mohr. The scattering of hydrogen molecules, especially at low temperatures, shows some deviation from the results predicted by the same theory. In the case of both hydrogen and helium it is necessary to assume collision radii larger than the corresponding kinetic theory values in order to obtain the best agreement between the calculated and observed curves.