Photoinduced surface dynamics

Photoinduced Surface Dynamics of CO Adsorbed on a Platinum Electrode... 

Noguchi, H., Okada, T. and Uosaki, K. (2006) Photoinduced surface dynamics of CO adsorbed on a platinum electrode. 

Z. G. Lan, E. Fabiano, and W. Thiel. Photoinduced nonadiabatic dynamics of pyrimidine nucle-obases on-the-fly surface-hopping study with semiempirical methods, J. Phys. Chem. B, 113 3548-3555 (2009). 

Nevertheless, detailed information on nudear wavepacket dynamics of surface adsorbates is important both from fundamental and from practical points of view. As is evidenced from the huge success of catalysis, solid surfaces sustain various kinds of reactions [8]. In order to understand the elementary steps of these reactions, the electronic and vibrational dynamics of surface adsorbates should be investigated in depth. Photochemistry at surfaces involves the photoinduced nuclear dynamics of adsorbates, which needs to be elucidated by ultrafast spectroscopy. Furthermore, combining with recently developed pulse shaping technologies [9], elucidation of the wavepacket dynamics will open up a novel laser control scheme of surface photochemical reactions. 

Overall the forward electron-transfer step must be much faster than all other photophysical decay mechanisms of the dye s excited state. The forward electron-transfer time should be >10 faster than the back-electron-transfer dynamics. The regeneration of the dye must be faster than both back electron transfer and the rate of photoinduced surface charging. The mechanism of regeneration and ensuing dynamics determines the required conditions for the back-electron-transfer rates. 

Muller, U., 8c Stock, G. (1997). Surface-hopping modeling of photoinduced relaxation dynamics on coupled potential-energy surfaces. Journal of Chemical Physics, 107(16), 6230-6245. 

Although the conductivity change Aa [relation (8)] of microwave conductivity measurements and the Ac of electrochemical measurements [relation (1)] are typically not identical (owing to the theoretically accessible frequency dependence of the quantities involved), the analogy between relations (1) and (8) shows that similar parameters are addressed by (photo)electrochemical and photoinduced microwave conductivity measurements. This includes the dynamics of charge carriers and dipoles, photoeffects, flat band and capacitive behavior, and the effect of surface states. 

To understand the fundamental photochemical processes in biologically relevant molecular systems, prototype molecules like phenol or indole - the chromophores of the amino acids tyrosine respective trypthophan - embedded in clusters of ammonia or water molecules are an important object of research. Numerous studies have been performed concerning the dynamics of photoinduced processes in phenol-ammonia or phenol-water clusters (see e. g. [1,2]). As a main result a hydrogen transfer reaction has been clearly indicated in phenol(NH3)n clusters [2], whereas for phenol(H20)n complexes no signature for such a reaction has been found. According to a general theoretical model [3] a similar behavior is expected for the indole molecule surrounded by ammonia or water clusters. As the primary step an internal conversion from the initially excited nn state to a dark 7ta state is predicted which may be followed by the H-transfer process on the 7ia potential energy surface. 

In this chapter we have surveyed recent experimental progress on the investigation of ultrafast nuclear wavepacket dynamics at surfaces. Nuclear (or vibrational) wavepackets of adsorbates are excited with ultrashort laser pulses, and subsequently their evolutions are probed with surface nonlinear spectroscopy such as 2PPE and SHG. These studies provide rich information on the initial stages of photoinduced... 

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