Blanchet Valérie, Raffael Kevin, Turri Giorgio, Chatel Béatrice, Girard Bertrand, Garcia Ivan Anton, Wilkinson Iain, Whitaker Benjamin J
Laboratoire Collisions Agrégats Réactivité, UMR 5589, CNRS, Institut de Recherches sur les Systèmes Atomiques et Moléculaires Complexes, UPS Toulouse, 31062 Toulouse Cedex 04, France.
J Chem Phys. 2008 Apr 28;128(16):164318. doi: 10.1063/1.2913167.
Pump-probe photoionization has been used to map the relaxation processes taking place from highly vibrationally excited levels of the S(2) state of azulene, populated directly or via internal conversion from the S(4) state. Photoelectron spectra obtained by 1+2(') two-color time-resolved photoelectron imaging are invariant (apart from in intensity) to the pump-probe time delay and to the pump wavelength. This reveals a photoionization process which is driven by an unstable electronic state (e.g., doubly excited state) lying below the ionization potential. This state is postulated to be populated by a probe transition from S(2) and to rapidly relax via an Auger-like process onto highly vibrationally excited Rydberg states. This accounts for the time invariance of the photoelectron spectrum. The intensity of the photoelectron spectrum is proportional to the population in S(2). An exponential energy gap law is used to describe the internal conversion rate from S(2) to S(0). The vibronic coupling strength is found to be larger than 60+/-5 microeV.
泵浦-探测光电离已被用于描绘从薁的S(2)态的高振动态激发能级发生的弛豫过程，这些能级是直接填充的，或者是通过从S(4)态的内转换填充的。通过1+2(')双色时间分辨光电子成像获得的光电子能谱对于泵浦-探测时间延迟和泵浦波长是不变的（除了强度）。这揭示了一个由位于电离势以下的不稳定电子态（例如，双激发态）驱动的光电离过程。假定该态是由从S(2)的探测跃迁填充的，并通过类似俄歇的过程迅速弛豫到高振动态激发的里德堡态。这解释了光电子能谱的时间不变性。光电子能谱的强度与S(2)中的布居数成正比。指数能隙定律被用于描述从S(2)到S(0)的内转换速率。发现振动电子耦合强度大于60±5微电子伏特。
