Departamento de Química-Física, Facultad de Ciencia y Tecnología, Universidad del País Vasco (UPV/EHU), Bilbao, Spain.
J Chem Phys. 2011 Aug 7;135(5):054308. doi: 10.1063/1.3615544.
The ultrafast relaxation of jet-cooled aniline was followed by time-resolved ionization, after excitation in the 294-234 interval. The studied range of energy covers the absorption of the two bright ππ∗ excitations, S(1) and S(3), and the almost dark S(2) (πσ∗) state. The employed probe wavelengths permit to identify different ultrafast time constants related with the coupling of the involved electronic surfaces. A τ(1) = 165 ± 30 fs lifetime is attributed to dynamics along the S(2) (πσ∗) repulsive surface. Other relaxation channels as the S(1)→S(0) and S(3)→S(1) internal conversion are also identified and characterized. The work provides a general view of the photophysics of aniline, particularly regarding the role of the πσ∗ state. This state appears as minor dissipation process due to the ineffective coupling with the bright S(1) and S(3) states, being the S(1)→S(0) internal conversion the main non-radiative process in the full studied energy range. Additionally, the influence of the off-resonance adiabatic excitation of higher energy electronic states, particularly S(3), is also observed and discussed.
喷气冷却苯胺的超快弛豫后，在 294-234 间隔内进行了时间分辨的离化。研究的能量范围涵盖了两个明亮的 ππ∗激发态 S(1)和 S(3)以及几乎暗的 S(2)（πσ∗）态的吸收。所采用的探测波长允许识别与涉及的电子表面耦合相关的不同超快时间常数。τ(1)=165±30fs 的寿命归因于沿着 S(2)（πσ∗）排斥表面的动力学。还识别和表征了其他弛豫通道，如 S(1)→S(0)和 S(3)→S(1)内转换。该工作提供了苯胺光物理的总体视图，特别是关于 πσ∗态的作用。由于与明亮的 S(1)和 S(3)态的无效耦合，该态表现为较小的耗散过程，S(1)→S(0)内转换是在整个研究的能量范围内主要的非辐射过程。此外，还观察和讨论了较高能量电子态（特别是 S(3)）的非共振绝热激发的影响。
