A semiclassical dynamics simulation for a long-lived excimer state of π-stacked adenines

Semiclassical dynamics simulation of the excitation of one of two π-stacked adenines by a 25 fs fwhm laser pulse was found to lead to the formation of a long-lived excimer, with an average C2– C 2 ′ distance of 2.2 Å. The C 2 ′ – N 3 ′ bond in the unexcited adenine was found to twist after the formation of excimer. The out-of-plane deformations of both C2 and C 2 ′ atoms play a significant role in the vibronic coupling, between the HOMO and LUMO, which leads to the deactivation of the excimer. This interaction is attributed to a face-to-face stacked configuration and a very short C2– C 2 ′ distance of 1.821 Å.