Authors Referees APS Members |
December 2007, to be published in Physical Review A
Dissociative recombination dynamics of the ozone cation
The dissociative recombination of the ozone cation has been studied at the heavy-ion storage ring CRYRING. The total cross section and branching fractions have been measured. The cross section from $\approx$0 eV to 0.2 eV follows a nearly $E^{-1}$ dependence, which was theoretically predicted to be a characteristic of the direct dissociative recombination mechanism. The thermal rate coefficient has been deduced from the cross section to be 7.37$\times$10$^{-7}$($T$/300)$^{-0.55}$ cm$^3$s$^{-1}$. The branching fraction analysis carried out at $\approx$0 eV interaction energy has shown a strong propensity (94\%) to dissociate through the three-body channel. Due to the overwhelming dominance of this channel it has been investigated in more detail. Of the six energetically available three-body pathways only three are significantly populated, such that the production of O($^1$S) is highly unfavoured and all atomic oxygen fragments are predominantly formed in $^3$P and $^1$D states. Analysis of the break-up geometries has been performed by means of the Dalitz plot. It is observed that the molecules dissociating through the O($^3$P)+O($^3$P)+O($^3$P) and O($^3$P)+O($^3$P)+O($^1$D) channels have an open linear geometry where cleavage of two valence bonds occurs preferentially in unison, while the O($^3$P)+O($^1$D)+O($^1$D) break-up might proceed partly through a sequential mechanism. © 2008 The American Physical Society.
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