Scattering of High Velocity Neutral Particles. X. He–N2; A–N2. The N2–N2 Interaction

Abstract

Total collision cross sections have been measured for helium atoms with energies between 500 and 2100 ev, and for argon atoms with the same energies, scattered in room temperature nitrogen. The results have been analyzed to obtain the average potential between a helium atom and a nitrogen molecule, $${\mathrm{〈V(r)〉}}_{\mathrm{Av}}{\text{=1.19×10}}^{\text{−10}}{\mathrm{/r}}^{\text{7.06}}\hspace{0.17em}\mathrm{ergs,}$$ for r between 1.79 A and 2.29 A, and the average potential between an argon atom and a nitrogen molecule, $${\mathrm{〈V(r)〉}}_{\mathrm{Av}}{\text{=1.21×10}}^{\text{−9}}{\mathrm{/r}}^{\text{7.78}}\hspace{0.17em}\mathrm{ergs},$$ for r between 2.28 A and 2.83 A. A procedure which takes into account the noncoincidence of the center of mass and the centers of force in the N₂ molecule has been developed for expressing these average atom‐molecule interactions as functions of the atom‐atom potential between the beam particle and either of the nitrogen atoms. These interatomic potentials have been combined with potentials previously determined for He–He and A–A to obtain a hypothetical potential between two nitrogen atoms in different N₂ molecules. The following average intermolecular potential for the N₂–N₂ system has been obtained by averaging such N–N interactions over all mutual orientations of the two N₂ molecules: $${\mathrm{〈V(r)〉}}_{\mathrm{Av}}{\text{=9.54×10}}^{\text{−10}}{\mathrm{/r}}^{\text{7.27\hspace{0.17em}}\mathrm{ergs}},$$ for r between 2.43 A and 3.07 A. This N₂–N₂ potential is consistent with one valid at larger separation distances, which has been derived from measurements on gaseous viscosity at high temperatures.