Topography of potential-energy surfaces. DIM (diatomics-in-molecules) surface for Cl + Cl2

Abstract

Potential-energy surfaces have been calculated over the full range of nuclear configurations for the C1+ C12 reaction using the DIM (diatomics-in-molecules) method with the 28 polyatomic basis functions of 2A' symmetry and the 26 of 2A" symmetry arising from three Cl(*P,) atoms. The lowest 2A' surface has its lowest potential-energy barrier Eb = 28 kJ mol-' in a configuration bent by ca. 35" from the collinear configuration with 'xi symmetry. The lowest 2A" surface has its lowest barrier Eb == 75 kJ mol-I in the collinear configuration with 211u symmetry. Comparison with previous calculations on the F + F2 reaction shows that the barrier heights are lower and the bent configuration more energetically favoured over the collinear configuration on the 2A' surface, in accord with Walsh molecular-orbital theory. However, the predicted increase in bending of the 2A' transition state for C13 compared with F3 is observed to only a small extent (ca. 5")

Direct observation and reactions of Cl3 radical

“…[17][18][19][20][21][22][23] Emission spectra attributable to Cl 3 were observed by Kawasaki et al 14 and Wright et al 15 These data were in reasonable agreement with each other. An IR spectrum of Cl 3 in a Kr matrix was reported by Nelson and Pimentel.…”

Reactive scattering of a supersonic fluorine atom beam: F + Cl2

“…DIM calculations have recently been undertaken [9] on the F + F 2 and C1 + C12 potential energy surfaces including spin orbit interaction, which indicate that some non-adiabatic transitions may occur between F(2P1/2) and F(2P3/z) spin multiplet states with splitting F(2P1/2)-F(2P3/2)= 5 kJ tool-1, in near collinear configurations in the entrance valley of the F + C12 potential energy surface. However reaction can proceed only on the lowest 2E+ 2A' potential energy surface which involves a shallow minimum, since the higher lying 21-I-2A', 2A" potential energy surfaces involve a significant barrier [7,8]. The 2~+-2-4' potential energy surface correlates with the CI(zP3/2) ground spin multiplet state of the product C1 atom.…”

“…Ab initio calculations on the C1F 2 radical [6] show it to be bent with an interbond angle fl-,~ 148 ~ and a C1-F bond length r e = 1'72A slightly extended over the bond length of the diatomic r~(ClF) = 1'63 A [-22]. Similarly DIM calculations on the F + F 2 [7] and C1 + el 2 [8] potential energy surfaces predict transition states which are bent with interbond angles fl ~ 150~ ~ and with the F-F and C1-C1 bond lengths slightly increased over the corresponding diatomic bond lengths [22]. Accordingly the structure of the F Cl-C1 complex may be estimated as shown in figure 5, together with an estimated reactant transition state having the same interbond angle fl and an gxtended C1-F bond length.…”

“…However this work has been confined to the heavier halogen atoms and molecules and theoretical estimates of the topography of the reaction potential energy surfaces have therefore been confined to the qualitative indications of Walsh [5] triatomic molecular orbital theory. The structure of the C1F 2 radical has been studied by ab initio methods [6] and potential energy surfaces have been calculated by the diatomics-in-molecules (DIM) method for the F + F 2 [7] and C1 + C12 [8], with spin orbit interaction being included in more recent calculations [9]. Calculations have also been reported on the full range of triatomic radicals involving F and C1 atoms using the MINDO method [I0].…”

Reactive scattering of a supersonic fluorine atom beam: F + Br2

“…Recent DIM calculations on the F + F 2 [15] and C1 + C12 [16] potential energy surfaces which have been extended to include spin orbit interaction [17], suggest that some non-adiabatic transitions may occur between the F(2Pt/2) and F(2P3/2) spin multiplet states in the entrance valley of the F + Br 2 potential energy surface due to the small spin orbit splitting F(2P1/2)-F(2p3/2)= 5 kJ mot -1. However the lowest 2E+-2A' potential energy surface correlates the reactant F(aP3/2) ground state with the Br(2p3/2) ground state product without an intervening energy barrier.…”