Detection of the Excited-State NH2 (Ã 2A1) in the Ultraviolet Photodissociation of Methylamine.

Abstract

Ion-imaging and dispersed fluorescence spectroscopy are employed for the photodissociation dynamics study of methylamine in the photolysis wavelength range 205-213 nm. The methyl radical product is found to populate a wide range of ro-vibrational states, among which the CH3 fragment generated in the v = 0 state shows a bimodal kinetic energy distribution. The internal energy analysis of the NH2 counterproduct indicates that a lower kinetic energy component, which was observed only with the CH3(v=0) fragment, energetically matches the electronically excited Ã2A1 state. The dispersed fluorescence spectrum, whose band structure is assigned to the Ã2A1 → X̃2B1 transition, provides evidence of the CH3(v=0) + NH2(Ã2A1) pathway. The branching mechanism of the product pathway is discussed in terms of nuclear dynamics in the long-range region, where the conical intersection between the excited- and ground-state potential energy surfaces can play a significant role.