Ultrafast optical dynamics

The chapter is organized as follows in Section 8.2 a brief overview of ultrafast optical dynamics in polymers is given in Section 8.3 we present m-LPPP and give a summary of optical properties in Section 8.4 the laser source and the measuring techniques are described in Section 8.5 we discuss the fundamental photoexcitations of m-LPPP Section 8.6 is dedicated to radiative recombination under several excitation conditions and describes in some detail amplified spontaneous emission (ASE) Section 8.7 discusses the charge generation process and the photoexcitation dynamics in the presence of an external electric field conclusions are reported in the last section. 

Ohta, K., M. Yang, and G. R. Fleming. 2001. Ultrafast exciton dynamics of J-aggregates in room temperature solution studied by third-order nonlinear optical spectroscopy and numerical simulations based on exciton theory. J. Chem. Phys. 115 7609-7621. 

Giraud, G., Gordon, C. M., Dunkin, 1. R., and Wynne, K., The effects of anion and cation substitution on the ultrafast solvent dynamics of ionic liquids A time-resolved optical Kerr-effect spectroscopic study, /. Chem. Phys., 119,464-477,2003. 

Since many of these developments reach into the molecular domain, the understanding of nano-structured functional materials equally necessitates fundamental aspects of molecular physics, chemistry, and biology. The elementary energy and charge transfer processes bear much similarity to the molecular phenomena that have been revealed in unprecedented detail by ultrafast optical spectroscopies. Indeed, these spectroscopies, which were initially developed and applied for the study of small molecular species, have already evolved into an invaluable tool to monitor ultrafast dynamics in complex biological and materials systems. The molecular-level phenomena in question are often of intrinsically quantum mechanical character, and involve tunneling, non-Born-Oppenheimer effects, and quantum-mechanical phase coherence. Many of the advances that were made over recent years in the understanding of complex molecular systems can therefore be transposed and extended to the study of... 

With site-directed mutation and femtosecond-resolved fluorescence methods, we have used tryptophan as an excellent local molecular reporter for studies of a series of ultrafast protein dynamics, which include intraprotein electron transfer [64-68] and energy transfer [61, 69], as well as protein hydration dynamics [70-74]. As an optical probe, all these ultrafast measurements require no potential quenching of excited-state tryptophan by neighboring protein residues or peptide bonds on the picosecond time scale. However, it is known that tryptophan fluorescence is readily quenched by various amino acid residues [75] and peptide bonds [76-78]. Intraprotein electron transfer from excited indole moiety to nearby electrophilic residue(s) was proposed to be the quenching... 

All the powerful methods of magnetic resonance, from solid-state nuclear magnetic resonance (NMR) to medical magnetic resonance imaging, depend on measuring the time evolution of a spin system following the application of one or more radio frequency pulses. In the visible and ultraviolet, ultrafast optical pulse sequences have been used for many years to measure both population dynamics and coherence phenomena. At low... 

Smith NA, Fin S, Meech SR, Yoshihara K. Ultrafast optical Kerr effect and solvation dynamics of liquid aniline. J Phys Chem A 1997 101 3641-3645. 

ULTRAFAST MAGNETIZATION DYNAMICS OF THIN Au/Fe FILMS NONLINEAR OPTICS STUDIES... 

Ultrafast magnetization dynamics of thin Au/Fe films nonlinear optics studies. 

Klimov V. I. (2000), Optical non-linearities and ultrafast carrier dynamics in semiconductor nanocrystals , J. Phys. Chem. B 104, 6112-6123. 

Transient terahertz spectroscopy Time-resolved terahertz (THz) spectroscopy (TRTS) has been used to measure the transient photoconductivity of injected electrons in dye-sensitised titanium oxide with subpicosecond time resolution (Beard et al, 2002 Turner et al, 2002). Terahertz probes cover the far-infrared (10-600 cm or 0.3-20 THz) region of the spectrum and measure frequency-dependent photoconductivity. The sample is excited by an ultrafast optical pulse to initiate electron injection and subsequently probed with a THz pulse. In many THz detection schemes, the time-dependent electric field 6 f) of the THz probe pulse is measured by free-space electro-optic sampling (Beard et al, 2002). Both the amplitude and the phase of the electric field can be determined, from which the complex conductivity of the injected electrons can be obtained. Fitting the complex conductivity allows the determination of carrier concentration and mobility. The time evolution of these quantities can be determined by varying the delay time between the optical pump and THz probe pulses. The advantage of this technique is that it provides detailed information on the dynamics of the injected electrons in the semiconductor and complements the time-resolved fluorescence and transient absorption techniques, which often focus on the dynamics of the adsorbates. A similar technique, time-resolved microwave conductivity, has been used to study injection kinetics in dye-sensitised nanocrystalline thin films (Fessenden and Kamat, 1995). However, its time resolution is limited to longer than 1 ns. 

Voisin, C., Del Fatti, N., Christofilos, D., Vallee, F. Ultrafast electron dynamics and optical nonlinearities in metal nanoparticles. J. Phys. Chem. B 105, 2264-2280 (2001)... 

This chapter focused on the role of photon polarization in producing ultrafast Jt-electron rotation by a single-color laser. If a two-color laser is employed, its relative optical phase can be another controlling factor for the rotation direction of Jt electrons [17, 39]. The next step is to extend the series of our studies to cover ultrafast nonadiabatic dynamics of chiral aromatic molecules in laser fields of arbitrary polarization. 

Hertel T, Knoesel E, Wolf M, Ertl G (1996) Ultrafast electron dynamics at Cu(ll 1) response of an electron gas to optical excitation. Phys Rev Lett 76 535-538... 

In Section 11.1.2 we argued that the solvation shell is not static. To probe the dynamics of the motion under the solvent-solute potential we need to displace the shell from equihbrium in a sudden manner. Ultrafast optical excitation of a solute from the ground state to an electronically excited state, particularly when the excited state has a very different dipole moment from the ground state, creates suitable initial conditions (see Figme 11.5). 

M. Cho, S. J. Rosenthal, N. F. Scherer, L. D. Ziegler, and G. R. Fleming, J. Chem. Phys., 96, 5033 (1992). Ultrafast Solvent Dynamics Connection between Time Resolved Fluorescence and Optical Kerr Measurements. 

In this chapter we describe advances in the femtosecond time-resolved multiphoton photoemission spectroscopy (TR-MPP) as a method for probing electronic structure and ultrafast interfacial charge transfer dynamics of adsorbate-covered solid surfaces. The focus is on surface science-based approaches that combine ultrafast optical pump probe excitation to induce nonlinear multi-photon photoemission (MPP) from clean or adsorbate covered single crystal surfaces. The photoemitted electrons transmit spectroscopic and dynamical information, which is captured by their energy analysis in real or reciprocal space. We examine how photoelectron spectroscopy and microscopy yield information on the unoccupied molecular structure, electron transfer and relaxation processes, light induced chemical and physical transformations and the evolution of coherent single particle and collective excitations at solid surfaces. 

Hu, Z. Huang, X. Armapureddy, H. V. R. Margulis, C. J. (2008). Molecular dynamics study of the temperatme-dependent optical Kerr effect spectra and intermolecular dynamics of room temperature ionic liquid 1-methoxyethylpyridinium dicyanoamide. Journal of Physical Chemistry B, 112, 7837-7849 Hunt, N. T. Jaye, A. A. Meech, S. R. (2007). Ultrafast dynamics in complex fluids observed through the ultrafast optically-heterodyne-detected optical-Kerr-effect (OHD-OKE), Physical Chemistry Chemical Physics, 9, 2167-2180 Hyun, B.-R. Dzyuba, S. V. Bartsch, R. A. Quitevis, E. L. (2002). Intermolecular dynamics of room-temperature ionic liquids femtosecond optical Kerr effect measurements on l-alkyl-3-ethylimidazoliinn bis((trifluoromethyl)sulfonyl)imides. Journal of Physical Chemistry A, 106, 7579-7585. 

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