The ab-initio calculation of the gas phase ion mobility of Na+ in N-2

A potential energy surface for the Na+-N-2 system calculated at the MP4SDTQ /6-311 + G(2df) level of theory in a rigid rotor approximation has been det ermined. The potential energy surface has an absolute minimum at theta = 0 degrees and R = 3.06 Angstrom of - 0.33 eV. R is the magnitude of the vecto r connecting the centre of mass of the N-2 molecule and the position of the Nai ion. The potential is expanded into its angular components in a trunca ted Legendre expansion. Transport cross-sections for the collisions of posi tive sodium ions with nitrogen molecules have been computed from the calcul ated interaction potential. These cross-sections have been combined with th e kinetic theory of atomic ions in polyatomic gases to calculate the mobili ty and diffusion coefficients parallel and perpendicular to an external ele ctric field. (C) 1999 Elsevier Science B.V. All rights reserved.