Energy transfer molecular

Flash Photolysis. Time-resolved spectroscopy techniques are a powerful means of studying materials, giving information about the nature of the excitations, energy transfer, molecular motion, and molecular environment, information that is not available from steady-state measurements. It is... 

Keywords Angular momentum Energy transfer Molecular collision dynamics... 

Wolfsberg s theoretical researches have focused on a variety of topics including quantum chemistry, isotope effects on thermodynamic properties and on chemical reaction rates, mass-spectrometric fragmentation patterns, translational-vibrational energy transfer, molecular dynamics calculations on condensed phases, and rotational-vibrational spectroscopy. 

Devices based on photo-induced energy transfer. Molecular wires can be... 

Following a transient disturbance the gas relaxes into an equilibrium distribution. One can follow this relaxation process in terms of the changes in the population of the different energy levels. Such changes are the manifestations of the energy-transferring molecular collisions. For example, a vihrationally excited HCl molecule can lose its excess energy in a collision with a vihrationally cold DCl molecule... 

Tsourkas, A. Behlke, M. A. Xu, Y. Bao, G. Spectroscopic features of dual fluorescence/luminescence resonance energy-transfer molecular beacons. Anal. Chem. 2003, 75, 3697-3703. 

M. Seibold, H. Port, and H. C. Wolf, Fulgides as light switches for intra-supermolecular energy transfer, Molecular Crystals and Liquid Crystals, vol. 283, no. 1, pp. 75-80, 1996. 

Davis M J 1995 Trees from spectra generation, analysis, and energy transfer information Molecular Dynamics and Spectroscopy by Stimulated Emission Pumping ed H-L Dai and R W Field (Singapore World Scientific)... 

Straub J E and Berne B J 1986 Energy diffusion in many dimensional Markovian systems the consequences of the competition between inter- and intra-molecular vibrational energy transfer J. Chem. Phys. 85 2999 Straub J E, Borkovec M and Berne B J 1987 Numerical simulation of rate constants for a two degree of freedom system in the weak collision limit J. Chem. Phys. 86 4296... 

For example, energy transfer in molecule-surface collisions is best studied in nom-eactive systems, such as the scattering and trapping of rare-gas atoms or simple molecules at metal surfaces. We follow a similar approach below, discussing the dynamics of the different elementary processes separately. The surface must also be simplified compared to technologically relevant systems. To develop a detailed understanding, we must know exactly what the surface looks like and of what it is composed. This requires the use of surface science tools (section B 1.19-26) to prepare very well-characterized, atomically clean and ordered substrates on which reactions can be studied under ultrahigh vacuum conditions. The most accurate and specific experiments also employ molecular beam teclmiques, discussed in section B2.3. 

The first classical trajectory study of iinimoleciilar decomposition and intramolecular motion for realistic anhannonic molecular Hamiltonians was perfonned by Bunker [12,13], Both intrinsic RRKM and non-RRKM dynamics was observed in these studies. Since this pioneering work, there have been numerous additional studies [9,k7,30,M,M, ai d from which two distinct types of intramolecular motion, chaotic and quasiperiodic [14], have been identified. Both are depicted in figure A3,12,7. Chaotic vibrational motion is not regular as predicted by tire nonnal-mode model and, instead, there is energy transfer between the modes. If all the modes of the molecule participate in the chaotic motion and energy flow is sufficiently rapid, an initial microcanonical ensemble is maintained as the molecule dissociates and RRKM behaviour is observed [9], For non-random excitation initial apparent non-RRKM behaviour is observed, but at longer times a microcanonical ensemble of states is fonned and the probability of decomposition becomes that of RRKM theory. 

In the case of polarized, but otherwise incoherent statistical radiation, one finds a rate constant for radiative energy transfer between initial molecular quantum states i and final states f... 

On the experimental side, small molecule energy transfer experiments may use molecular beam teclmiques [65. 66 and 67] (see also chapter C3.3 for laser studies). 

The dynamics of fast processes such as electron and energy transfers and vibrational and electronic deexcitations can be probed by using short-pulsed lasers. The experimental developments that have made possible the direct probing of molecular dissociation steps and other ultrafast processes in real time (in the femtosecond time range) have, in a few cases, been extended to the study of surface phenomena. For instance, two-photon photoemission has been used to study the dynamics of electrons at interfaces [ ]. Vibrational relaxation times have also been measured for a number of modes such as the 0-Fl stretching m silica and the C-0 stretching in carbon monoxide adsorbed on transition metals [ ]. Pump-probe laser experiments such as these are difficult, but the field is still in its infancy, and much is expected in this direction m the near fiitiire. 

Sharma R D and Brau C A 1969 Energy transfer in near-resonant molecular collisions due to long-range forces with application to transfer of vibrational energy from the mode of CO2 to N2 J. Chem. Phys. 50 924-30... 

Cottrell T L and McCoubrey J C 1961 Molecular Energy Transfer in Gases (London Butterworths)... 

Yardley J T 1980 Introduction to Molecular Energy Transfer (New York Aoademio)... 

More recently Andrews and Juzeliunas [6, 7] developed a unified tlieory that embraces botli radiationless (Forster) and long-range radiative energy transfer. In otlier words tliis tlieory is valid over tire whole span of distances ranging from tliose which characterize molecular stmcture (nanometres) up to cosmic distances. It also addresses tire intennediate range where neitlier tire radiative nor tire Forster mechanism is fully valid. Below is tlieir expression for tire rate of pairwise energy transfer w from donor to acceptor, applicable to transfer in systems where tire donor and acceptor are embedded in a transparent medium of refractive index ... 

Master equation methods are not tire only option for calculating tire kinetics of energy transfer and analytic approaches in general have certain drawbacks in not reflecting, for example, certain statistical aspects of coupled systems. Alternative approaches to tire calculation of energy migration dynamics in molecular ensembles are Monte Carlo calculations [18,19 and 20] and probability matrix iteration [21, 22], amongst otliers. 

Demidov A A 1999 Use of Monte-Carlo method in the problem of energy migration in molecular complexes Resonance Energy Transfer e6 D L Andrews and A A Demidov (New York Wiley) pp 435-65... 

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