Theoretical and experimental studies of the N2O− and N2O ground state potential energy surfaces. Implications for the O−+N2→N2O+e and other processes

Abstract

The ground state potential energy surface of the nitrous oxide negative ion is characterized and related to that of the neutral molecule by a synergetic theoretical–experimental approach. Ab initio multiconfiguration self-consistent-field/configuration interaction (MCSCF/CI) and other calculations for N2O−(X 2A′) yield the minimum energy geometry (ReNN, ReNO, AeNNO) = (1.222±0.05 Å, 1.375±0.10 Å, 132.7±2°), the vibrational frequencies (ν1,ν2,ν3) = (912±100 cm−1, 555±100 cm−1, 1666±100 cm−1), the dipole moment μ =2.42±0.3 D, and other properties. The N2O− molecular ion in the X 2A′ state is found to have a compact electronic wavefunction—one with very little diffuse character. The MCSCF/CI bending potential energy curve from 70° to 180° for the X 1Σ+(1 1A′) state of N2O as well as the bending curve for the X 2A′ state of N2O− are also reported. The dissociation energy D (N2–O−) =0.43±0.1 eV and, thus, the adiabatic electron affinity E.A.(N2O) =0.22±0.1 eV and the dissociation energy D (N–NO−) =5.1±0.1 eV are determined from beam–collision chamber experiments. Corrections are made for both the dispersion in the ion beam and the translational motion of each target gas. The combined theoretical and experimental results yield a vertical electron affinity V.E.A.(N2O) of −2.23±0.2 eV and enable the construction of angular dependent Morse functions to represent the neutral and ionic surfaces. This construction leads to the determination of the minimum intersection locus as (V*, R*NN, R*NO, A*NNO) = (0.67±0.1 eV, 1.18±0.05 Å, 1.28±0.10 Å, 154±3°). The predicted activation energy of this critical point with respect to the asymptote O−, N2—0.21±0.1 eV—and the position of the critical point with R*NN well outside of the N2 (v=0) outer turning point imply that the reaction O−+N2→N2O+e will be strongly facilitated by reagent vibrational excitation.

Dissociation of Molecules by Slow Electrons

“…(222) It was suggested(223.224) that excitation of the bending mode leads to the capture of electrons with very low energy, and that in the bent configuration the ground state of N20-is stable against electron emission. This suggestion was confirmed by the quantal calculations by Hopper et al (225) Studies of the angular distributions of the 0-produced from N20 have also been made, (224) giving information on the partial waves that are involved in the electron capture step.…”

Reaction rates of the hydrated electron with N2O in high temperature water and potential surface of the N2O− anion

“…This disparity was resolved by Chantry [26], who showed that the results depend on pressure. While the adiabatic electron affinity of N 2 O in the gas phase is assigned to be +0.22 eV [8], there are both experimental and theoretical results on the electron affinity that disagree with this value (for e.g., [9][10][11]), and the reason for this disparity has not been determined.…”

“…While there has been considerable interesting research on the electron attachment to N 2 O in the gas phase [2][3][4][5][6][7][8][9][10][11][12], the presence of solvent molecules will significantly alter the electron affinity, molecular structure and chemical reactivity of N 2 O. One cannot apply the gas phase data to an N 2 O solution.…”

Chemiluminescence from the Ba(P3)+N2O→BaO(A Σ1+)+N2 reaction: Collision energy effects on the product rotational alignment and energy release

“…III A͒, with calculated thresholds of 5.85 and 11.55 eV, respectively, using D͑N 2 -O͒ = 1.74 eV, 33 a Ba͑ 1 S 0 ͒ ionization potential of 5.21 eV, 42 and a N 2 O vertical electron affinity ͑VEA͒ of Ϫ2.23 eV. 43 The latter threshold, along with the possible production of BaO + above 6.91 eV, suggests that a broad range of collision energies could lead to reaction, especially considering the high efficiency of the Ba͑ 3 P͒ beam source.…”