Highly Rotationally Excited CH3from Methane Photodissociation through Conical Intersection Pathway

Abstract

Photodissociation of CH4 has been studied using the high-resolution Rydberg tagging time-of-flight technique. The TOF spectra show an important single C-H bond fission channel with partially resolved sharp features. Careful simulations indicate that these sharp peaks are due to highly rotationally excited CH3 products, which are likely produced through a conical intersection dissociation pathway between the excited and ground potential energy surfaces. The energy-dependent anisotropy parameter of the CH3 product has also been determined at various photolysis wavelengths. The results of this work show that the conical intersection between the S-1 and S-0 surfaces plays an essential role in the photochemistry of CH4.