Thermodynamics of NO⁺·N₂:  Atmospheric Relevance

Abstract

The NO + ‚N 2 cationic complex is studied using high-level ab initio calculations. The geometry is found to be a skewed T shape, with two linear stationary points corresponding to the N-O + ‚N-N and N-N‚N-O + configurations. At the highest level of theory, CCSD(T)/aug-cc-pVQZ//CCSD(T)/aug-cc-pVTZ, the interaction energy is estimated to be 1950 cm -1 (5.6 kcal mol -1 ), from which a ∆H 298 interaction enthalpy value of 4.9 kcal mol -1 was derived. By using the well-established heat of formation of NO + , it was possible to derive a standard ∆H f 298 value of 230.4 kcal mol -1 for NO + ‚N 2 . In addition, the enthalpy, entropy, free energy and equilibrium constants were calculated for the dissociation of the complex, as a function of altitude, for the earth's atmosphere.

The intermolecular potential in NO–N2 and (NO–N2)+ systems: implications for the neutralization of ionic molecular aggregates

“…The D e value of 252 meV compares very well with the best estimate of Solda´n et al (243 meV). 34 Also the DH 298 interaction enthalpy value of 223 meV is in very good agreement with the value of 212 meV obtained by the same authors. 34 This is the global minimum found on the singlet potentialenergy surface of (NON 2 ) + .…”

“…34 Also the DH 298 interaction enthalpy value of 223 meV is in very good agreement with the value of 212 meV obtained by the same authors. 34 This is the global minimum found on the singlet potentialenergy surface of (NON 2 ) + . We tried to find other minima optimizing the (NON 2 ) + geometry with symmetry constraints; in particular, we considered linear geometries with the connectivity N-O-N-N and O-N-N-N, but both structures show an imaginary frequency.…”

The Ã←X̃(1+1)REMPI spectrum and high-level ab initio calculations of the complex between NO and N2

“…•N 2 has been studied recently using ab initio calculations, 50,51 and is found to have a skewed T-shaped structure with the N 2 pointing towards the NO center-ofmass. The binding energy was estimated to be 1950 cm Ϫ1 , which is far greater than that of the X or à states.…”

(2 + 1) REMPI spectroscopy of the NO–CO, NO–N2, and NO–{N2, Ar} van der Waals complexes in the region of the 4s and 3d Rydberg states

“…22,23 It is expected that the motions will be of large amplitude, and that therefore the Franck-Condon factors will be concentrated around those of the more-tightly-bound excited state. Since the binding energy of NO + -N 2 (1700 cm À1 ) 18 is around double that of NO + -Ar (940 cm À1 ), 16 we expect N 2 to have the stronger interaction with the NO + core; also, given the large red shift of the NO-{N 2 , Ar} spectrum relative to that of NO-N 2 (and that this spectrum is itself red shifted with respect to uncomplexed NO-see Fig. 1), it would appear that both the N 2 and the Ar are located inside the Rydberg orbital and are both interacting strongly with the NO + core.…”

“…Calculations of the ion geometries for both NO + -CO and NO + -N 2 have suggested global minima corresponding to a skewed T-shape geometry. 18,19 For the NO + -CO case, linear saddle points were identified, lying 1276-1644 cm À1 above the zero point energy. Thus, a very high barrier to rotation occurs in the ion state.…”