Issue 7, 2014

Roads leading to roam. Role of triple fragmentation and of conical intersections in photochemical reactions: experiments and theory on methyl formate

Abstract

The exploration of alternative roads that open to molecules with sufficient energy to yield different products permits prediction and eventually control of the outcomes of chemical reactions. Advanced imaging techniques for monitoring laser-induced photodissociation are here combined with dynamical simulations, involving ample sets of classical trajectories generated on a quantum chemical potential energy surface. Methyl formate, HCOOCH3, is photodissociated at energies near the triple fragmentation threshold into H, CO and OCH3. Images of velocity and rotational distributions of CO exhibit signatures of alternative routes, such as those recently designated as transition-state vs. roaming-mediated. Furthermore, a demonstration of the triple fragmentation route is given, and also confirmed by H-atom product imaging and FTIR time-resolved spectra of the intermediate HCO radical. In addition, the relevance of nonadiabatic transitions promoted by a conical intersection is clarified by simulations as the privileged “reactivity funnel” of organic photochemistry, whereby the outcomes of molecular photoexcitation are delivered to electronic ground states.

Graphical abstract: Roads leading to roam. Role of triple fragmentation and of conical intersections in photochemical reactions: experiments and theory on methyl formate

Article information

Article type
Paper
Submitted
05 Sep 2013
Accepted
07 Nov 2013
First published
11 Nov 2013

Phys. Chem. Chem. Phys., 2014,16, 2854-2865

Roads leading to roam. Role of triple fragmentation and of conical intersections in photochemical reactions: experiments and theory on methyl formate

P. Tsai, M. Chao, T. Kasai, K. Lin, A. Lombardi, F. Palazzetti and V. Aquilanti, Phys. Chem. Chem. Phys., 2014, 16, 2854 DOI: 10.1039/C3CP53792G

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