Energy transport, molecular

FIGURE 3.11 Core definition. After redistribution of energy at the molecular scale, core size is suggested by the distance at which energy transported by secondary electrons just exceeds that due to every other channel (see text for details). From Mozumder and La Verne (1987). 

Schwarzer D, Kutne P, Schroder C, Troe J (2004) Intramolecular vibrational energy redistribution in bridged azulene-anthracene compounds ballistic energy transport through molecular chains. J Chem Phys 121 1754... 

The future targets of supramolecular photochemistry in CD chemistry will contain photoresponsive molecular machines, emission-based sensors, and energy transport systems. For construction of such systems, the design of three-dimen-sionally correct arrangement of component units will become important. The molecular modeling computation approach will be helpful for designing the systems and deeper understanding of structural features of chromophore-modified CDs and their complexes. 

In this part of the thesis, we will combine the theoretical aspects of the previous section with experimental aspects of charge/energy transport and focus on the molecular wire-like transport from the mechanistic point of view. 

In this thesis, we will focus on molecules as individual wires. It is, nevertheless, important to point out, that electron and energy transport in higher dimensional molecular materials (such as polymers or molecular crystals) is closely interconnected. Many of the mechanisms that have been discussed in this thesis, such as coherent tunneling, thermal hopping, Forster transfer, etc., are present in both the single-wire systems and in molecular materials. 

If we can expect that the eddy momentum and energy transport will both be increased in the same proportion compared with their molecular values, we might anticipate that heat-transfer coefficients can be calculated by Eq. (5-56) with the ordinary molecular Prandtl number used in the computation. It turns out that the assumption that Pr, = Pr is a good one because heat-transfer calculations based on the fluid-friction analogy match experimental data very well. For this calculation we need experimental values of C/ for turbulent flow. 

Mean free path indicates the transfer of momentum, energy, or mass a distance. In the steady state, the net transport equals zero. These forces, or transfer functions, always act to bring a system back to the steady state. This implies (1) diffusion from high concentration to low concentration, (2) heat conduction from hot to cold, and (3) momentum flow—mass motion energy to molecular motion (hence accompanied by a rise in temperature of the gas). 

There is a close connection between molecular mass, momentum, and energy transport, which can be explained in terms of a molecular theory for low-density monatomic gases. Equations of continuity, motion, and energy can all be derived from the Boltzmann equation, producing expressions for the flows and transport properties. Similar kinetic theories are also available for polyatomic gases, monatomic liquids, and polymeric liquids. In this chapter, we briefly summarize nonequilibrium systems, the kinetic theory, transport phenomena, and chemical reactions. 

However, changes in the potential energy of intermolecular interactions are not uniquely separable. There is an ambiguity in defining the heat flow for open systems. We may split u into a diffusive part and a conductive part in several ways and define various numbers of heat flows. In the molecular mechanism of energy transport, the energy... 

The nature of energy transport and percolation has been examined in mixed molecular crystals which are regarded as fractal structures S0. Strong guest host interaction produces induced energy funnels which are found to mask the fractal nature of the... 

The transport of mass, momentum and energy through a fluid are the consequences of molecular motion and molecular interaction. At the macroscopic level, associated with the transport of each dynamic variable is a transport coefficient or property, denoted by X, such that the flux, J, of each variable is proportional to the gradient of a thermodynamic state variable such as concentration or temperature. This notion leads to the simple phenomenological laws such as those of Pick, Newton and Fourier for mass, momentum or energy transport, respectively. 

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