Ultrafast dynamics of aniline in the 294-234 nm excitation range: The role of the πσ state

• Published in: The Journal of chemical physics 2011-08, Vol.135 (5), p.054308-054308-8
• Main Authors: Montero, Raúl, Conde, Álvaro Peralta, Ovejas, Virginia, Martínez, Roberto, Castaño, Fernando, Longarte, Asier
• Format: Article
• Language: English
• Subjects: Aniline Compounds - chemistry; Electrons; Photochemical Processes; Quantum Theory
• ISSN: 0021-9606; 1089-7690
• 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.