Attention is focused on the Na+. N-2 complex as part of a study of Na+-cont
aining complexes, which have been implicated in the formation of sporadic s
odium layers in the upper atmosphere. The equilibrium structure is found to
be linear, in agreement with previous studies. A potential energy hypersur
face is calculated at the CCSD(T)/aug-cc-pVTZ level of theory, where the N-
2 moiety is held fixed, but a wide range of Jacobi bond lengths and bond an
gles are sampled. This hypersurface is fitted to an analytic form and from
this anharmonic vibrational separations are calculated, and compared to har
monic values. Rovibrational energy levels are also calculated from the fitt
ed hypersurface. The best estimate of the interaction energy, Delta E-e is
2770 cm(-1), and Delta H-f(298)(Na+. N-2) = (136.5 +/- 2.0) kcal mol(-1). (
C) 1999 American Institute of Physics. [S0021-9606(99)30632-2].