Non-adiabatic dynamics of Rydberg-excited diethylamine

Femtosecond time-resolved photoelectron spectroscopy was employed to investigate the ultrafast non-adiabatic dynamics of diethylamine (DEA). Following the direct excitations of the two main conformational structures (i.e., TT and TG) of DEA to the 3p Rydberg states at 200 nm, DEA undergoes internal conversion to the 3s state with similar to 68 fs, which is similar to previously relaxation pathways of several secondary and tertiary amines. Subsequent dynamics on the 3s Rydberg state evolves along the N-H stretching coordinate and is then accompanied by the breaking of the N-H bond in about 120 fs, rather than the cleavage of the N-C, or C-C bonds as well as the conformational transformations between the TT and TG conformers on the 3s states. Theoretically, we reveal the pre-dissociative n sigma* character evolving along the N-H stretching coordinate within the 3s state as DEA dissociates to yield H atom products. As contrasted to the well-known conformational N-C bond rotation motions in systems such as tertiary amines, the non-adiabatic relaxation of the 3s state of DEA is predominantly characterized by the N-H bond dissociation process.(c) 2022 Elsevier B.V. All rights reserved.