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Science 8 August 2008:
Vol. 321. no. 5890, pp. 826 - 830
DOI: 10.1126/science.1157617
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Reports

The Role of Excited-State Topology in Three-Body Dissociation of sym-Triazine

John D. Savee,1 Vadim A. Mozhayskiy,2 Jennifer E. Mann,1 Anna I. Krylov,2* Robert E. Continetti1*

Molecular fragmentation into three products poses an analytical challenge to theory and experiment alike. We used translational spectroscopy and high-level ab initio calculations to explore the highly debated three-body dissociation of sym-triazine to three hydrogen cyanide molecules. Dissociation was induced by charge exchange between the sym-triazine radical cation and cesium. Calculated state energies and electronic couplings suggest that reduction initially produces a population of sym-triazine partitioned between the 3s Rydberg and {pi}* <- n electronically excited manifolds. Analysis of the topology of these manifolds, along with momentum correlation in the dissociation products, suggests that a conical intersection of two potential energy surfaces in the 3s Rydberg manifold leads to stepwise dissociation, whereas a four-fold glancing intersection in the {pi}* <- n manifold leads to a symmetric concerted reaction.

1 Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA.
2 Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA.

* To whom correspondence should be addressed. E-mail: krylov{at}usc.edu (A.I.K.); rcontinetti{at}ucsd.edu (R.E.C.)

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Science. ISSN 0036-8075 (print), 1095-9203 (online)