The ab-initio calculation of the gas phase ion mobility of Na+ in N2 Original Research Article

A potential energy surface for the Na+–N2 system calculated at the MP4SDTQ/6-311+G(2df) level of theory in a rigid rotor approximation has been determined. The potential energy surface has an absolute minimum at θ=0° and R=3.06 Å of −0.33 eV. R is the magnitude of the vector connecting the centre of mass of the N2 molecule and the position of the Na+ ion. The potential is expanded into its angular components in a truncated Legendre expansion. Transport cross-sections for the collisions of positive sodium ions with nitrogen molecules have been computed from the calculated interaction potential. These cross-sections have been combined with the kinetic theory of atomic ions in polyatomic gases to calculate the mobility and diffusion coefficients parallel and perpendicular to an external electric field.