State ultrafast

Wokosin D L, Centonze V, White J G, Armstrong D, Robertson G and Ferguson A I 1996 All-solid-state ultrafast lasers facilitate multiphoton excitation fluorescence imaging IEEE J. Sel. Top. Quantum Electron. 21051-65... 

Developments in laser sources have been essential for the advances in CARS microscopy (Cheng and Xie 2004). Recent CARS microscopy studies have relied on solid-state ultrafast lasers, and have evolved from low-repetition-rate femtosecond... 

The label thermal can apply to any of the ET types just described and implies that the initial state is at thermal equilibrium (i.e., all the molecular and medium modes are at thermal equilibrium with the given electronic state). Ultrafast PIET processes may be sufficiently fast (ultrafast) that the equilibrium assumption is no longer valid [11]. 

Fe(CO)4 proceeds, that is, Fe(CO)s— excited Fe(CO)s— Fe(CO)4— Fe(CO)4, or Fc(CO)5— excited Fe(CO)5 — excited Fe(CO)s— Fe(CO)4. Fe(CO)4 was not observed in the low-temperature matrix experiments. Femtosecond UV laser excitation with time-of-flight mass spectrometric detection was able to show that photolysis of Fe(CO>5 at 267 nm proceeds via an excited singlet state to yield (in ca. 30 fs) Fe(CO)4, initially in an excited singlet state, which then rapidly decays to the lowest singlet state.Ultrafast electron diffraction experiments were able to determine a more precise structure of Fe(CO>4 and confirm the singlet pathway. 

Time-resolved resonance Raman spectrometry is a technique that allows collection of Raman spectra of excited state moleeules. It has been used to study intermediates in enzyme reactions, the spectra of carotenoid excited states, ultrafast electron transfer steps, and a variety of other biological and bioinorganic processes. Time-discrimination methods have been used to overcome a major limitation of resonance Raman spectroscopy, namely, fluorescence interference either by the analyte itself or by other species present in the sample. 

A MAS NMR technique for transferring polarization from protons to a specific set of the spins has been introduced for the study of biomole-cular samples in the solid-state. Ultrafast (>60kHz) MAS and low irradiation rf fields are used to achieve band-selective Hartmann-Hahn CP between the whole proton bath and carbons whose resonances are close to... 

A combination of solid-state NMR techniques and theoretical calculations has been used by Kobayashi et ah to confirm that unsubstituted metal-free corroles form supramolecular systems with toluene through 71-71 interactions in the solid state. Ultrafast MAS enabled the use of... 

According to Kramers model, for flat barrier tops associated with predominantly small barriers, the transition from the low- to the high-damping regime is expected to occur in low-density fluids. This expectation is home out by an extensively studied model reaction, the photoisomerization of tran.s-stilbene and similar compounds [70, 71] involving a small energy barrier in the first excited singlet state whose decay after photoexcitation is directly related to the rate coefficient of tran.s-c/.s-photoisomerization and can be conveniently measured by ultrafast laser spectroscopic teclmiques. 

Mohrschladt R, Schroeder J, Troe J, Vdhringer P and Votsmeier M 1994 Solvent influence on barrier crossing in the S. -state of c/s- and trans- st ff stiibene Ultrafast Phenomena /Xed P F Barbara et al (New York Springer) pp 499-503... 

Plenary 11. W Kiefer et al, e-mail address wolfgang.kiefer mail.imi-wue.de (TR CARS). Ultrafast impulsive preparation of ground state and excited state wavepackets by impulsive CARS with REMPI detection in potassium and iodine duners. 

These limitations have recently been eliminated using solid-state sources of femtosecond pulses. Most of the femtosecond dye laser teclmology that was in wide use in the late 1980s [11] has been rendered obsolete by tliree teclmical developments the self-mode-locked Ti-sapphire oscillator [23, 24, 25, 26 and 27], the chirped-pulse, solid-state amplifier (CPA) [28, 29, 30 and 31], and the non-collinearly pumped optical parametric amplifier (OPA) [32, 33 and 34]- Moreover, although a number of investigators still construct home-built systems with narrowly chosen capabilities, it is now possible to obtain versatile, nearly state-of-the-art apparatus of the type described below Ifom commercial sources. Just as home-built NMR spectrometers capable of multidimensional or solid-state spectroscopies were still being home built in the late 1970s and now are almost exclusively based on commercially prepared apparatus, it is reasonable to expect that ultrafast spectroscopy in the next decade will be conducted almost exclusively with apparatus ifom conmiercial sources based around entirely solid-state systems. 

Yu J and Berg M 1992 Solvent-electronic state interactions measured from the glassy to the liquid state. I. Ultrafast transient and permanent hole burning in glycerol J. Chem. Phys. 96 8741-9... 

Chudoba C, Riedle E, Pfeiffer M and Elsaesser T 1996 Vibrational coherence in ultrafast excited-state proton transfer Cham. Phys. Lett. 263 622-8... 

Bardeen C J, Che J, WIson K R, Yakovlev V V, Cong P, Kohler B, Krause J L and Messina M 1997 Quantum control of Nal photodissociation reaction product states by ultrafast tailored light pulses J. Phys. Chem. A 101 3815-22... 

In light of tire tlieory presented above one can understand tliat tire rate of energy delivery to an acceptor site will be modified tlirough tire influence of nuclear motions on tire mutual orientations and distances between donors and acceptors. One aspect is tire fact tliat ultrafast excitation of tire donor pool can lead to collective motion in tire excited donor wavepacket on tire potential surface of tire excited electronic state. Anotlier type of collective nuclear motion, which can also contribute to such observations, relates to tire low-frequency vibrations of tire matrix stmcture in which tire chromophores are embedded, as for example a protein backbone. In tire latter case tire matrix vibration effectively causes a collective motion of tire chromophores togetlier, witliout direct involvement on tire wavepacket motions of individual cliromophores. For all such reasons, nuclear motions cannot in general be neglected. In tliis connection it is notable tliat observations in protein complexes of low-frequency modes in tlie... 

For /2(Ar)i7, an extensive CI-CSP simulation was carried out, and the results were compared with those of the simple CSP approximation. Both calculations are for the ultrafast dynamics following excitation of the I2 into the B state. We found that the CI-CSP calculation, including doubly excited configurations , is close to converged for times up to t 500 fs, when 1500 configurations are included. Fig. 2 shows co(t)p, the coefficient of the CSP term and the doubly excited terms in the full CI-CSP wavefunction,... 

The role of disorder in the photophysics of conjugated polymers has been extensively described by the work carried out in Marburg by H. Bassler and coworkers. Based on ultrafast photoluminescence (PL) (15], field-induced luminescence quenching [16J and site-selective PL excitation [17], a model for excited state thermalizalion was proposed, which considers interchain exciton migration within the inhomogenously broadened density of states. We will base part of the interpretation of our results in m-LPPP on this model, which will be discussed in some detail in Sections 8.4 and 8.6. 

The purpose of this work is to demonstrate that the techniques of quantum control, which were developed originally to study atoms and molecules, can be applied to the solid state. Previous work considered a simple example, the asymmetric double quantum well (ADQW). Results for this system showed that both the wave paeket dynamics and the THz emission can be controlled with simple, experimentally feasible laser pulses. This work extends the previous results to superlattices and chirped superlattices. These systems are considerably more complicated, because their dynamic phase space is much larger. They also have potential applications as solid-state devices, such as ultrafast switches or detectors. 

Easy availability of ultrafast high intensity lasers has fuelled the dream of their use as molecular scissors to cleave selected bonds (1-3). Theoretical approaches to laser assisted control of chemical reactions have kept pace and demonstrated remarkable success (4,5) with experimental results (6-9) buttressing the theoretical claims. The different tablished theoretical approaches to control have been reviewed recently (10). While the focus of these theoretical approaches has been on field design, the photodissociation yield has also been found to be extremely sensitive to the initial vibrational state from which photolysis is induced and results for (11), HI (12,13), HCl (14) and HOD (2,3,15,16) reveal a crucial role for the initial state of the system in product selectivity and enhancement. This critical dependence on initial vibrational state indicates that a suitably optimized linear superposition of the field free vibrational states may be another route to selective control of photodissociation. 

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