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Abstract
Constrained optimizations in the space of S1/S0 intersection are used to map the seam of degeneracy at which the singlet-excited state of fulvene undergoes radiationless decay to the ground state. The relevant seam of intersection lies along a coordinate composed of methylene torsion and C–C bond inversion, and connects the conical intersection (CI) minima of C 2 v and C 2 symmetry. These results are consistent with a previous second derivative analysis of the CI minima, and also with MMVB dynamics, for which decay to the ground state occurs at all twisted angles. The constrained optimizations are carried out using a conical intersection optimization algorithm based on projected gradients. The constraint is applied before projection, in order to avoid optimization errors due to cancellation between the components of the composite optimization gradient.
∥Dedicated to Mike Robb on his 60th birthday.
Acknowledgements
The authors thank Mike Robb for continuous support. L. B. is financed by the Ramón y Cajal program from the MCyT and by Grants No. BQU2002-04112-C02-02 and BQU2002-03334 from the Dirección General de Investigación (MCyT). M. J. B. gratefully acknowledges a travel award to visit Girona from the HPC-Europa Transnational Access programme, administered by CEPBA (Barcelona).
Notes
∥Dedicated to Mike Robb on his 60th birthday.