Interaction between light and matter

Bioinorganic Photochemistry Grazyna Stochel, Malgorzata Brindell, Wojciech Macyk, Zofia Stasicka, Konrad Szacilowski 2009 Grazyna Stochel, Malgorzata Brindell, Wojciech Macyk, Zofia Stasicka, Konrad Szacilowski. ISBN 978-1405-16172-5 

Artificial sources of incoherent radiation functioning continuously involve  

The spectral characteristic of this light depends on the kind of the source the incandescent lamps are used primarily as sources of polychromatic visible light characterized by a continuous spectrum electrical discharge lamps produce band or line spectra in UV, visible and near-IR regions, whereas resonance lamps emit resonance radiation of atoms and their ions in the form of line spectra and can be used as sources of monochromatic light, eg Hg (184.9 and 253.7nm), Cd (228.8 and 643.8nm), Na (589.0nm), Zn (213.8, 330.0, 334.5, and 636.2nm), Kr (116.5 and 123.6nm), Xe (129.6 and 147.0nm) [1]. 

Sources of pulsed incoherent radiation are so-called flash lamps, which produce short light pulses of broadband continuous-wave characteristic. Commonly, an intense pulse of short duration is used to generate sufficient concentration of a transient species suitable for spectroscopic observation. 

For photochemical purposes only absorption and luminescence are of importance absorption is the main method of excited state generation, whereas luminescence belongs to photophysical processes, which compete with the photoreactions in the excited state deactivation. 

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Vibrational spectroscopy is based on the interaction between light and matter it probes the different vibrational states of the investigated molecules. A number of excellent books describing the principles, instrumentation and applications are available [7,8]. 

From the stereochemical point of view, (3 characterizes a chiral compound similar to the classical rotatory power [a]0. However, the two quantities have a different origin The optical rotation is a consequence of the chiral interaction between light and matter, while the cholesteric induction originates from a... 

What is the nature of the interaction between light and matter that causes certain wavelengths of light to be absorbed The answer lies in the structure of the atoms and molecules of which matter is composed. First consider atoms. The modem theory of the atom states that electrons exist in energy levels around... 

The discovery of self-focussing of intense laser beams 318 ) and the phenomena of self-induced transparency 318b) have stimulated a whole new class of experimental investigations which give information about the transient interaction between light and matter 318c)... 

Our understanding of the interaction between light and matter is governed and limited by the Heisenberg uncertainty principle which may be stated as... 

The interaction between light and matter can be viewed as the creation of a coherent quantum superposition of initial and final electron states that has an associated polarization [3], as shown in Figure 1. The coherence between states with different wave vector requires an intermediate virtual state and the presence of a coherent phonon. A transition between the initial and final states may occur when the coherence of the system is broken either due to the finite width of an optical wave packet or by scattering from the environment. The transition results in the absorption of a photon and the creation of a hot electron-hole pair. Otherwise, the photon is re-radiated with a different phase and, perhaps, polarisation. 

Scandola F, Balzani V. Interaction between light and matter. In Serpone N, Pelizzetti E, eds. Photocatalysis Fundamentals and Application. New York Wiley-Interscience, 1989 9 14. 

Abstract Photochemistry is concerned with the interaction between light and matter. The present chapter outlines the basic concepts of photochemistry in order to provide a foundation for the various aspects of environmental photochemistry explored later in the book. Electronically excited states are produced by the absorption of radiation in the visible and ultraviolet regions of the spectrum. The excited states that can be produced depend on the electronic structure of the absorbing species. Excited molecules can suffer a variety of fates together, these fates make up the various aspects of photochemistry. They include dissociation, ionization and isomerization emission of luminescent radiation as fluorescence or phosphorescence and transfer of energy by intramolecular processes to generate electronic states different from those first excited, or by intermo-lecular processes to produce electronically excited states of molecules chemically different from those in which the absorption first occurred. Each of these processes is described in the chapter, and the ideas of quantum yields and photonic efficiencies are introduced to provide a quantitative expression of their relative contributions. 

In order to investigate solids or polymer systems with free carriers by IR spectroscopy, it is very convenient to measure the reflectivity instead of absorbance or transmittance. Thus, the problems to be discussed in this context are usually described by a linear response formalism. In its simplest form, this means that the response function (dielectric function) s(u ) of a damped harmonic oscillator is used to describe the interaction between light and matter. The complex form of this function is... 

The interactions between light and matter at a surface include absorption, reflection, phase shift, and diffraction. The... 

The interaction between light and matter, rmlike thermal activation of compounds in the form of heat, is always a very selective process. Photochemical activation may induce the twisting, stretching, or destabilization of certain bonds located in a specific region of an individual molecule, while other subrmits remain... 

Molecular nonlinear optics is the description of the change of the molecular optical properties by the presence of an intense light field. Since light either can be considered a classical electromagnetic wave or as a stream of photons, we may describe the interaction between light and matter in two apparently different ways, and we will start by considering how linear and nonlinear optical phenomena can be described in these two frameworks. 

NLO phenomena result from the interaction between light and matter and, more precisely, between the polarisable electron density and the strong electric field associated with a very intense laser beam. They were experimentally observed firstly in 1961 just after the development of intense laser sources in particular by Kaiser and Garett for two-photon absorption and by Fra n ken for They can be divided in two... 

Phototransduction based on interactions between light and matter... 

PHOTOTRANSDUCTION BASED ON INTERACTIONS BETWEEN LIGHT AND MATTER... 

It is probably safe to say that there is really no satisfactory mathematical description that can fully account for all of the possible interactions between light and matter, particularly in complex biological media. Two common interactions are illustrated in figure 4.2. Although Newton incorrectly explained the principle of refraction, it is now understood that light changes speed and direction when passing from one medium to another. The index of refraction is defined as... 

Figure 4.2 Two common interactions between light and matter, (a) At certain angles, light is refracted when passing from one medium to another (at dashed line), changing direction and velocity, (b) When light hits a particle, elastic collisions result in changes in direction and phase (Rayleigh scattering), whereas inelastic collisions result in frequency changes (Raman effect).

Interaction between light and matter in a non-absorbing medium... 

The interaction between light and matter is a complex phenomenology that has been theoretically solved a long time ago. but has been applied to wide range instrumentation techniques only very recently because of computational problems that could not be solved quickly prior to the arrival of digital computers. 

Photophysics and photochemistry deal with the interaction between light and matter. This is of immediate interest to ns, since the nutrients that we need originate in natural photosynthesis. Fnrthermore, it has become very important to develop solar cells for electric energy prodnction. 

A variety of functions can also be obtained from the interaction between light and matter in artificial systems. The type and utility of such functions depend on the degree of complexity and organization of the chenfical systems that receive and process the photons. 

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