Imaging studies of the CH3 fragments formed in the ultraviolet photodissociation of dimethylamine: Role of the parent 3s and 3p Rydberg states.

[Display omitted] • The ion-imaging study was performed for photodissociation of dimethylamine. • Two kinetic energy components of the methyl radical product were measured. • The calculation revealed the potential energy curves for N–CH 3 and N–H dissociations. State-resolved ion-imaging of the CH 3 product of dimethylamine photolysis in the 3s and 3p Rydberg bands (200–235 nm) revealed bimodal CH 3 velocity distributions with a fast portion disappearing at the longer photolysis wavelength. The fast component is assigned to direct dissociation based on the calculated potential energy curves. The slow component is assigned to indirect dissociation via N–H channel conical intersection with subsequent CH 3 dissociation. The origin of the threshold wavelength near 225 nm was attributed to the N–CH 3 bond rupture energy barrier on the S 1 (3s) state, implying an increasing contribution of direct dissociation at the shorter photolysis wavelengths. [ABSTRACT FROM AUTHOR]