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Published on: June 27, 2014
Excitation wavelength dependent S1-state decay dynamics of 2-aminopyridine and 3-aminopyridine
Baihui Feng1,2,3, Dongyuan Yang1, Yanjun Min1,3
1State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, Liaoning 116023, China. yangdy@dicp.ac.cn.
Abstract:
The decay dynamics of 2-aminopyridine and 3-aminopyridine excited to the S1 state is investigated using femtosecond time-resolved photoelectron imaging. The lifetime of the S1 state for both molecules shows a rapid decrease with the increase of the vibrational energy. It is shown that, besides intersystem crossing to the lower-lying triplet state of T1, the decay to the ground state (S0) via internal conversion through a conical intersection plays an increasingly important role and becomes dominant for vibrational states well above the S1 state origin. The comparison between 2-aminopyridine and 3-aminopyridine suggests that the intramolecular hydrogen bonding between a hydrogen atom of the NH2 group and the heterocyclic nitrogen atom in 2-aminopyridine effectively hinders the ring deformation at lower vibrational states which is required for the wavepacket to reach the S1/S0 conical intersection, and therefore slows down the S1 to S0 internal conversion.
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