The Scattering of a Beam of Potassium Atoms in Various Gases

A narrow beam of neutral K atoms was scattered in H₂, He, Ne, N₂, A and CO₂ at low pressures. The distribution of the scattered K atoms about the original beam was measured by the Langmuir-Taylor surface ionization detector. The experimental conditions were sufficiently refined that K atoms suffering very small angular deviations (down to about 4. 5' of arc) were counted as scattered atoms. The computed "effective collision radii" when compared with the values expected from the quantum theory of elastic sphere collisions show good agreement for H₂ and He. For the other gases, the experimental values are much larger, indicating the existence of considerable interatomic attractive forces even for Ne and A.