Conical intersection seam and bound resonances embedded in continuum observed in the photodissociation of thioanisole-d(3)

Abstract

Herein, the multi-dimensional nature of the conical intersection seam has been experimentally revealed in the photodissociation reaction of thioanisole-d(3) (C6H5SCD3) excited on S-1, giving C6H5S center dot((A) over tilde or (X) over tilde) + center dot CD3 products. The translational energy distribution of the nascent center dot CD3 fragment, reflecting the relative yields of the C6H5S center dot((A) over tilde) and C6H5S center dot((X) over tilde) products, was measured at each S-1 vibronic band using the velocity map ion imaging technique. Direct access of the reactant flux to the conical intersection seam leads to the increase of the nonadiabatic transition probability resulting in sharp resonances in the (X) over tilde/(A) over tildeC(6)H(5)S center dot product branching ratio at several distinct S-1 vibronic bands. The nature of the S-1 vibronic bands associated with such dynamic resonances was clarified by the mass-analyzed threshold ionization spectroscopy. The bound state embedded in continuum generated by the conical intersection is observed as a distinct dynamic resonance, revealing the nature of the nuclear motion responsible for the nonadiabatic coupling of two potential energy surfaces at the conical intersection. The multi-dimensional facets of the conical intersection seam in terms of its detailed structure and dynamic role are discussed with the aid of theoretical calculations.