Dynamics of molecules near ionization

In this paper, we report our experimental studies, using femtosecond-resolved mass spectrometry, and theoretical calculations of the potential energy surfaces, using density functional theory, for 10 aliphatic amines (substituted ammonia) excited directly near the ionization continuum. By probing parent and fragment masses, we are able to decipher pathways of the reactive alpha-cleavage and the nonreactive internal conversion, a precursor for the following chemistry. The bifurcation in these channels is related to the structure, as evidenced by the dramatic effect of alpha-substitution vs N-substitution on the time scale of the dynamics-femtosecond vs picosecond rates. For all molecules studied, the observed branching is dependent on the change of character of the state, ionic and/or neutral, along the reaction coordinate, and this change blurs the distinction between Rydberg and Superexcited states in their subsequent reactivity.