Conical intersections dynamics

Toniolo A, Olsen S, Manohar L, Martinez TJ (2004) Conical intersection dynamics in solution the chromophore of green fluorescent protein. Faraday Discuss 127 149... 

PolU D, Altoe P, Weingart O, SpUlane KM, Manzoni C, Brida D, Tomasello G, Orlandi G, Kukura P, Mathies RA, GaraveUi M, Cerullo G (2010) Conical intersection dynamics of the primary photoisomerization event in vision. Nature 467 440-443... 

X, y, z describe the orientation and shape of the double cone. The relation between these attributes and the near conical intersection dynamics has been discussed previously for nonrelativistic conical intersection. For the conical intersections encountered here, —s... 

Instead of trying to obtain each surface individually at a highly accurate level, we here resort to the much simpler scheme of complete active space self consistent field (CASSCF). Together with the phenomenological diabatization scheme of Sec. 5.2.1.2, the potential surfaces are computed at fairly low cost. Several accurate potential surfaces have been computed for the NO2 system by other groups as stated above. By comparison we conclude that features relevant to the conical intersection dynamics are well represented already at the CASSCF level. 

Time-resolved photoelectron spectroscopy of the conical intersection dynamics in the NO2 system... 

In Refs. [466] and [221], the transient grating interferometry signal from the conical intersection dynamics in NO2 (see Sec. 5.4.1.2) was measured for a 401 nm (3.09 eV), FWHM 40 fs pump pulse. The left panel of Fig. 5.33 shows the time-dependence of Im= , t) for the 13th harmonic, which re-hects the time evolution of the diabatic excited state population (Fig. 5.33, right). In the case of ionization out of the same orbital and spatially spread vibrational waveftmction as in the present case, the dependence of di Q,t) on the molecular geometry (vibrational dynamics) was found to be small... 

Conical Intersection Dynamics in Solution The Chromophore of Green Fluorescent Protein. 

The stoi7 begins with studies of the molecular Jahn-Teller effect in the late 1950s [1-3]. The Jahn-Teller theorems themselves [4,5] are 20 years older and static Jahn-Teller distortions of elecbonically degenerate species were well known and understood. Geomebic phase is, however, a dynamic phenomenon, associated with nuclear motions in the vicinity of a so-called conical intersection between potential energy surfaces. 

Conical intersections can be broadly classified in two topological types peaked and sloped [189]. These are sketched in Figure 6. The peaked case is the classical theoretical model from Jahn-Teller and other systems where the minima in the lower surface are either side of the intersection point. As indicated, the dynamics of a system through such an intersection would be expected to move fast from the upper to lower adiabatic surfaces, and not return. In contrast, the sloped form occurs when both states have minima that lie on the same side of the intersection. Here, after crossing from the upper to lower surfaces, recrossing is very likely before relaxation to the ground-state minimum can occur. 

Other studies have also been made on the dynamics around a conical intersection in a model 2D system, both for dissociahve [225] and bound-state [226] problems. Comparison between surface hopping and exact calculations show reasonable agreement when the coupling between the surfaces is weak, but larger errors are found in the shong coupling limit. 

For the mechanistic studies made, this protocol is able to give information about how dynamical properties affect the evolution of a photochemical reaction, but is not accurate enough for quantitative results. The information obtained relates to aspects of the surface such as the relative steepness of regions on the lower slopes of the conical intersection, and the relative width of alternative channels. 

The first study in which a full CASSCE treatment was used for the non-adiabatic dynamics of a polyatomic system was a study on a model of the retinal chromophore [86]. The cis-trans photoisomerization of retinal is the primary event in vision, but despite much study the mechanism for this process is still unclear. The minimal model for retinal is l-cis-CjH NHj, which had been studied in an earlier quantum chemisti7 study [230]. There, it had been established that a conical intersection exists between the Si and So states with the cis-trans defining torsion angle at approximately a = 80° (cis is at 0°). Two... 

The full quantum mechanical study of nuclear dynamics in molecules has received considerable attention in recent years. An important example of such developments is the work carried out on the prototypical systems H3 [1-5] and its isotopic variant HD2 [5-8], Li3 [9-12], Na3 [13,14], and HO2 [15-18], In particular, for the alkali metal trimers, the possibility of a conical intersection between the two lowest doublet potential energy surfaces introduces a complication that makes their theoretical study fairly challenging. Thus, alkali metal trimers have recently emerged as ideal systems to study molecular vibronic dynamics, especially the so-called geometric phase (GP) effect [13,19,20] (often referred to as the molecular Aharonov-Bohm effect [19] or Berry s phase effect [21]) for further discussion on this topic see [22-25], and references cited therein. The same features also turn out to be present in the case of HO2, and their exact treatment assumes even further complexity [18],... 

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