Energy radiative

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... 

A3.13.3.2 THE MASTER EQUATION FOR COLLISIONAL AND RADIATIVE ENERGY REDISTRIBUTION UNDER CONDITIONS OF GENERALIZED FIRST-ORDER KINETICS... 

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 ... 

Radiative heat transfer is perhaps the most difficult of the heat transfer mechanisms to understand because so many factors influence this heat transfer mode. Radiative heat transfer does not require a medium through which the heat is transferred, unlike both conduction and convection. The most apparent example of radiative heat transfer is the solar energy we receive from the Sun. The sunlight comes to Earth across 150,000,000 km (93,000,000 miles) through the vacuum of space. FIcat transfer by radiation is also not a linear function of temperature, as are both conduction and convection. Radiative energy emission is proportional to the fourth power of the absolute temperature of a body, and radiative heat transfer occurs in proportion to the difference between the fourth power of the absolute temperatures of the two surfaces. In equation form, q/A is defined as ... 

Noncontact Interactions (Nonradiative and Radiative Energy Transfer).197... 

As seen from (1) and (2), intermolecular processes may reduce essentially the lifetime and the fluorescence quantum yield. Hence, controlling the changes of these characteristics, we can monitor their occurrence and determine some characteristics of intermolecular reactions. Such processes can involve other particles, when they interact directly with the fluorophore (bimolecular reactions) or participate (as energy acceptors) in deactivation of S) state, owing to nonradiative or radiative energy transfer. Table 1 gives the main known intermolecular reactions and interactions, which can be divided into four groups ... 

Thus, this mechanism requires that A must be capable of absorbing the photon emitted by D that is, the acceptor absorption spectrum must overlap with the donor emission spectrum. Radiative energy transfer can operate over very large distances because a photon can travel a long way and A simply intercepts the photon emitted by D. ... 

Since the photon emitted by D is absorbed by A, the same rules will apply to radiative energy transfer as to the intensity of absorption. Because singlet-triplet transitions are spin-forbidden and singlet-triplet absorption coefficients are usually extremely small, it is not possible to build up a triplet state population by radiative energy transfer. For this... 

Finally, there is a specific red-edge effect related to non-radiative energy transfer between a donor fluorophore whose emission spectrum overlaps the absorption spectrum of an acceptor fluorophore in rigid polar solutions, there is a lack of energy transfer upon excitation at the red-edge. This effect, called Weber s effect, will be described in Section 9.4.3. 

Perrin s model has been used in particular for the interpretation of non-radiative energy transfer in rigid media (see Chapter 9). 

The use of Forster non-radiative energy transfer for measuring distances at a supramolecular level (spectroscopic ruler) will be discussed in detail in Chapter 9. 

Further details of non-radiative energy transfer will be presented in Chapter 9, together with various applications. 

Emission inner filter effect (self-absorption) The fluorescence photons emitted in the region overlapping the absorption spectrum can be absorbed (radiative energy trans-... 

We have considered so far non-radiative energy transfer from a donor to an acceptor that is a different molecule (heterotransfer). Energy transfer between like molecules is also possible (homotransfer) if there is some overlap between the absorption and fluorescence spectra. 

The rate of radiant thermal energy transfer between two bodies is described by the Stefan-Boltzmann law. Originally proposed in 1879 by Joseph Stefan and verified in 1884 by Ludwig Boltzmann, the Stefan-Boltzmann law states thatthe emission of thermal radiative energy is proportional to the fourth power of the absolute temperature (Kelvin or Rankine) ... 

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