From quantum chemistry to dissociation kinetics: what we need to know ^†

^†The Molecular Physics Lecture presented at the 23rd Colloquium on High Resolution Molecular Spectroscopy, Budapest, August 2013.

Figures & data

Figure 1. Falloff curves of the rate constants k _at for non-dissociative electron attachment to SF₆ (modelling from Ref. [8]; dashed lines: only collisional stabilisation, full lines: collisional plus radiative stabilisation of SF₆ ^−*).

Figure 2. Specific rate constants for electron detachment (k _det, SF₆ ⁻ → SF₆ + e⁻) and dissociation (k _dis, SF₆ ⁻ → SF₅ ⁻ + F) of SF₆ ^−* (modelling from Ref. [10]; the energies E should be decreased by 0.17 eV after re-evaluation [6] of E _a).

Figure 3. Dissociative electron attachment cross sections of SF₆ as a function of electron energy E _el and gas temperature T _gas (experimental points from Ref. [11]; modelling from Ref. [10], dashed curves: total cross sections).

Figure 4. Branching fractions R = [SF₅ ⁻] / ([SF₆ ⁻] + [SF₅ ⁻]) for dissociative electron attachment to SF₆ (filled experimental points after 4 ms of reaction time, open experimental points after 14 ms, from Ref. [4]; low-pressure decrease of R: collisional stabilisation of primary SF₆ ^−*, high-pressure increase of R: collisional thermal dissociation of SF₆ ⁻ after primary collisional stabilisation of primary SF₆ ^−*).

Figure 5. Falloff curves for H + CH₃ (+ M) → CH₄ (+ M) (full lines: modelling from Ref. [13], experimental data given in Ref. [13]).

Figure 6. Falloff curves for CH₄ (+ M) → CH₃ + H (+ M) (M = CH₄, modelling from Ref. [13], experimental data given in Ref. [13]).

Figure 7. Falloff curves for CH₄ (+ M) → CH₃ + H (+ M) (M = Ar, T = 2200 K; full and dashed lines: modelling from Ref. [14], experimental data given in Ref. [14]).

Figure 8. High-pressure limiting rate constants for CH₄ → CH₃ + H (theoretical modelling from Ref. [14]; lines: modelling with potential of Equation (3.1) and C/D = 2.5, points: modelling with the ab initio potential of Refs [16, 17]; upper line and points: isotropic potential, i.e. PST, lower line, and points: anisotropic potential).

Figure 9. Dependence of transitional mode frequencies on the C–C bond length r in C₂F₄ (quantum-chemical calculations from Ref. [30], α/Å⁻¹ = anisotropy parameter, see the text).

Figure 10. High-pressure limiting rate constants for 2 CF₂ → C₂F₄ (line: SACM/CT calculations from Ref. [30] with α/β ≈ 0.23, experimental data given in Ref. [30]).

Figure 11. Minimum-energy path potential V(R) for HO₂ → H + O₂ (a ₀ = 0.529 Å, from Ref. [32]; points and full line: ab initio potential of Ref. [31], dashed and dotted lines: simpler analytical potentials, see Ref. [32]).

Figure 12. Transition-state switching in the adiabatic channel potential curves V_i (R) for HO₂ → H + O₂ (SACM calculations from Ref. [32]; B = 1.446 cm⁻¹, dash–dotted line: MEP potential of Figure 11, other lines: channel potentials for l = j = 1, 3, 5, … from bottom to top, see Ref. [32]).

Figure 13. Capture rate constants k _cap for H + O₂ → HO₂ (from Ref. [32], dashed line: with isotropic long-range potential, upper full line: PST with MEP potential of Figure 11, lower full line: with anisotropic ab initio potential from Ref. [31]).

Figure 14. Falloff curves for H + O₂ + M → HO₂ + M (from Ref. [28], M = N₂, experimental points given in Ref. [28], T = 300, 400, …, 900, and 1200 K from bottom to top).

Figure 15. Long-range potential energy curves for C + HO → CHO (from Ref. [34], numbers = Ω values).

Figure 16. Association rate constants for C + HO → CHO (from Ref. [35]; k _ass = k _rec,∞, dashed line: calculation with single electronic state and Equation (4.1), full line: calculation with full mixing of electronic states accounting for spin–orbit and rotronic coupling).

Figure 17. Experimental (points) and modelled (lines) low temperature rate constants for HO + O → H + O₂ (from the Kinetic Database for Astrochemistry (KIDA) [38]).

Figure 18. Rate constants for HO + O → H + O₂ (various models from Ref. [40] compared with experimental points, for details see Ref. [40]; high temperature points from the reverse reaction converted with the equilibrium constant).

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