Kirkby Oliver M, Sala Matthieu, Balerdi Garikoitz, de Nalda Rebeca, Bañares Luis, Guérin Stéphane, Fielding Helen H
Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
Phys Chem Chem Phys. 2015 Jul 7;17(25):16270-6. doi: 10.1039/c5cp01883h. Epub 2015 May 20.
Femtosecond time-resolved photoelectron spectroscopy experiments have been used to compare the electronic relaxation dynamics of aniline and d7-aniline following photoexcitation in the range 272-238 nm. Together with the results of recent theoretical investigations of the potential energy landscape [M. Sala, O. M. Kirkby, S. Guérin and H. H. Fielding, Phys. Chem. Chem. Phys., 2014, 16, 3122], these experiments allow us to resolve a number of unanswered questions surrounding the nonradiative relaxation mechanism. We find that tunnelling does not play a role in the electronic relaxation dynamics, which is surprising given that tunnelling plays an important role in the electronic relaxation of isoelectronic phenol and in pyrrole. We confirm the existence of two time constants associated with dynamics on the 1(1)πσ* surface that we attribute to relaxation through a conical intersection between the 1(1)πσ* and 1(1)ππ* states and motion on the 1(1)πσ* surface. We also present what we believe is the first report of an experimental signature of a 3-state conical intersection involving the 2(1)ππ*, 1(1)πσ* and 1(1)ππ* states.
飞秒时间分辨光电子能谱实验已被用于比较苯胺和d7-苯胺在272 - 238纳米范围内光激发后的电子弛豫动力学。结合最近对势能面的理论研究结果[M. Sala, O. M. Kirkby, S. Guérin和H. H. Fielding, Phys. Chem. Chem. Phys., 2014, 16, 3122]，这些实验使我们能够解决一些围绕非辐射弛豫机制的未解决问题。我们发现隧穿在电子弛豫动力学中不起作用，鉴于隧穿在等电子的苯酚和吡咯的电子弛豫中起重要作用，这一发现令人惊讶。我们证实了与1(1)πσ表面上的动力学相关的两个时间常数的存在，我们将其归因于通过1(1)πσ和1(1)ππ态之间的锥形交叉点的弛豫以及在1(1)πσ表面上的运动。我们还展示了我们认为是涉及2(1)ππ*、1(1)πσ和1(1)ππ态的三态锥形交叉点的实验特征的首次报道。
