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

State-resolved ion-imaging of the CH3 product of dimethylamine photolysis in the 3s and 3p Rydberg bands (200-235 nm) revealed bimodal CH3 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 CH3 dissociation. The origin of the threshold wavelength near 225 nm was attributed to the N-CH3 bond rupture energy barrier on the S1(3s) state, implying an increasing contribution of direct dissociation at the shorter photolysis wavelengths.

Automated summary

State-resolved ion-imaging of the CH3 product of dimethylamine photolysis in the 3s and 3p Rydberg bands reveals bimodal velocity distributions, with a fast component attributed to direct dissociation and a slow component attributed to indirect dissociation. The study also suggests an increasing contribution of direct dissociation at shorter photolysis wavelengths.