Extended conical intersection seam

The Extended Conical Intersection Seam Applications in Photochemistry 403... 

THE EXTENDED CONICAL INTERSECTION SEAM APPLICATIONS IN PHOTOCHEMISTRY... 

However, the initial excitation is to the enol S2 7jr-7jr state. It is clear from Figure 9.25 that there is an extended conical intersection seam between the ln-7nl6n-8n excited states and the ground state. Thus, the system can decay... 

Blancafort L, Robb MA. A valence bond description of the prefulvene extended conical intersection seam of benzene. J Chem Theory Comput. 2012 8 4922-4930. Blancafort L, Celani P, Beatpark M, Robb M. A valence-bond-based complete-active-space self-consistent-field method for the evaluation of bonding in organic molecules. Theor Chem Acc. 2003 110 92-99. 

Serrano-Perez JJ, Bearpark MJ, Robb MA. The extended S-1 /S-0 conical intersection seam for the photochemical 2+2 cycloaddition of two ethylene molecules. Mol Phys. 2012 110 2493-2501. 

Quantum dynamics simulations were run within a nine-dimensional model subspace including the nine most important modes displayed on Fig. 10 and a fivedimensional model including only the pseudo-branching-plane modes 1 and 15, and the three out-of-plane photoactive modes 4, 16x, and 16 j [31,53]. The results were interpreted with regard to the topological features of the extended seam of conical intersection and their influence on the photoreactivity. This is illustrated with Fig. 11. 

So an alternative mechanism is followed corresponding to bond formation in an asynchronous fashion, involving the formation of one bond completely on the excited-state surface. From Figure 3.25, we can see that this occurs via a transition state, which leads to a conical intersection. This conical intersection is a seam that extends through 1,3 (meta) and 1,4... 

Siciha F, Blancafort L, Bearpark MJ, Robb MA. Quadratic description of conical intersections Characterization of critical points on the extended seam.J Phys Chem A. 2007 111 2182-2192. 

This chapter sets out to focus on the information available from computational tools to describe non-adiabatic dynamics and photochemical reactivity. From a general mechanistic point of view the non-adiabatic event takes place near a conical intersection. It is the shape of the extended seam of the intersection and its position on the reaction path that controls the outcome of a photochemical reaction. The concepts of this topic are reviewed, with examples, in Sect. 7.2. In Sect. 7.3 we introduce the main methods for performing dynamics using a potential derived from quantum chemistry electronic structure methods, starting from an exact solution of... 

Calculations on model cyanines (H2N-(CH) -NH2+ with n = 3, 5 or 7) showed [86,87] (1) a systematic relationship between the size of the polymethine chain and the time scale of the cis-trans torsion (2) an extended seam of conical intersection along the torsional coordinates and (3) that high-frequency skeletal deformations were required to access the seam. The last two points were demonstrated with qualitative results based on semi-classical trajectories for the simplest trimethine cyanine (see Fig. 7.10). 

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