Showing papers by "Yu Harabuchi published in 2015"
TL;DR: The intrinsic reaction coordinate (IRC) approach has been used extensively in quantum chemical analysis and prediction of the mechanism of chemical reactions as mentioned in this paper, which gives a unique connection from a given transition structure to local minima of the reactant and product sides.
Abstract: The intrinsic reaction coordinate (IRC) approach has been used extensively in quantum chemical analysis and prediction of the mechanism of chemical reactions. The IRC gives a unique connection from a given transition structure to local minima of the reactant and product sides. This allows for easy understanding of complicated multistep mechanisms as a set of simple elementary reaction steps. In this article, three topics concerning the IRC approach are discussed. In the first topic, the first ab initio study of the IRC and a recent development of an IRC calculation algorithm for enzyme reactions are introduced. In the second topic, cases are presented in which dynamical trajectories bifurcate and corresponding IRC connections can be inaccurate. In the third topic, a recent development of an automated reaction path search method and its application to systematic construction of IRC networks are described. Finally, combining these three topics, future perspectives are discussed. © 2014 Wiley Periodicals, Inc.
267 citations
TL;DR: Minimum energy conical intersection geometries were searched for polycyclic aromatic hydrocarbons and the energy barriers to the obtained MECIs showed a correlation with their fluorescence quantum yields, providing a theoretical rationale for the size dependence of the fluorescence Quantum yields seen in these PAHs.
Abstract: Minimum energy conical intersection (MECI) geometries were searched for polycyclic aromatic hydrocarbons (PAHs) consisting of up to 26 atoms. The energy barriers to the obtained MECIs showed a correlation with their fluorescence quantum yields. This provides a theoretical rationale for the size dependence of the fluorescence quantum yields seen in these PAHs.
46 citations
TL;DR: Using 42 nm high harmonic pulses, the dissociation dynamics of 1,2-butadiene was investigated by time-resolved photoelectron spectroscopy (TRPES), enabling us to observe dynamical changes of multiple molecular orbitals with higher temporal resolution than conventional light sources.
Abstract: Using 42 nm high harmonic pulses, the dissociation dynamics of 1,2-butadiene was investigated by time-resolved photoelectron spectroscopy (TRPES), enabling us to observe dynamical changes of multiple molecular orbitals (MOs) with higher temporal resolution than conventional light sources. Because each lower-lying occupied MO has particular spatial electron distribution, the structural dynamics of photochemical reaction can be revealed. On the femtosecond time scale, a short-lived excited state with a lifetime of 37 ± 15 fs and the coherent oscillation of the photoelectron yield stimulated by Hertzberg-Teller coupling were observed. Ab initio molecular dynamics simulations in the electronically excited state find three relaxation pathways from the vertically excited structure in S1 to the ground state, and one of them is the dominant relaxation pathway, observed as the short-lived excited state. On the picosecond time scale, the photoelectron yields related to the C-C bond decreased upon photoexcitation, indicating C-C bond cleavage.
19 citations
TL;DR: The detailed mechanisms of bifurcations related to the VRTs are discussed by surveying a landscape of the global reaction route map, and the connectivity of VRT points and minima is clarified.
Abstract: A global reaction route map is generated for Au5 by the anharmonic downward distortion following method in which 5 minima and 14 transition states (TSs) are located Through vibrational analyses in the 3N − 7 (N = 5) dimensional space orthogonal to the intrinsic reaction coordinate (IRC), along all the IRCs, four IRCs are found to have valley-ridge transition (VRT) points on the way where a potential curvature changes its sign from positive to negative in a direction orthogonal to the IRC The detailed mechanisms of bifurcations related to the VRTs are discussed by surveying a landscape of the global reaction route map, and the connectivity of VRT points and minima is clarified Branching of the products through bifurcations is confirmed by ab initio molecular dynamics simulations starting from the TSs A new feature of the reaction pathways, unification, is found and discussed
14 citations
TL;DR: The existence of a valley-ridge transition point along the intrinsic reaction coordinate does not always indicate the existence of two minima in the product side, but VRT is a sign of bifurcating nature of dynamical trajectories running on the potential energy surface.
Abstract: The existence of a valley-ridge transition (VRT) point along the intrinsic reaction coordinate does not always indicate the existence of two minima in the product side, but VRT is a sign of bifurcating nature of dynamical trajectories running on the potential energy surface. It is demonstrated by molecular dynamics simulations.
2 citations