Electromagnetic radiation incoherent

Conventional sources of electromagnetic radiation are incoherent, which means that the waves associated with any two photons of the same wavelength are, in general, out-of-phase and have a random phase relation with each other. Laser radiation, however, has both spatial and temporal coherence, which gives it special importance for many applications. 

Tab. 3.3 Spectral domains of electromagnetic radiation (VUV, UV, VIS and IR), energy conversions, principle emission lines of mercury arc lamps, and of some novel incoherent excimer lamps...

In addition, a novel generation of lamps with promising features for photochemical applications has been developed to industrial maturity over the last decade, the so-called incoherent excimer radiation sources (Eliasson et al., 1988). Note that these lamps are not laser sources. In contrast to well-known excimer lasers, excimer lamps are operated under different physical conditions and they emit incoherent electromagnetic radiation. Whereas pulsed laser radiation can reach very high irradiances, E up to 100 MW m , the irradiance E of excimer lamps is only in the range of 1000 W m . ... 

In the H2O-VUV AOP no additional auxiliary oxidants must be used to produce sufficient amounts of OH radicals. The technical development of incoherent exci-mer VUV and UV sources of electromagnetic radiation (see Chapter 4.3) led to a renaissance of research related to water photolysis. Hence, the experimental conditions and results of several recent investigations that deal with the applications of VUV and UV incoherent excimer lamps in the field of AOP research (mainly in aqueous media) are briefly summarized in Tab. 7-2. 

The computation of far-field radiation from a collection of incoherently radiating dipoles is in general quite a complicated problem. To calculate the angular dependence of the far-field intensity, the volume distribution of excited states must first be obtained, which, as we have seen, depends on the volume distribution of the absorbers and the electromagnetic field which stimulates them. The fields in turn depend on the frequency and linewidth of the exciting light source. Then the emission problem for the excited-state distribution (both spatial and frequency) must be solved including reorientation and depolarization effects. 

In contrast to coherent radiation emitted by laser sources, incoherent or non-co-herent radiation is characterized by elementary electromagnetic waves that do not have any phase relation in space and time. The production of incoherent excimer radiation in the UV or VUV region of the electromagnetic spectrum is made pos-... 

The electrons enter the wiggler/undulator in unstructured packets (e.g. storage ring case) or in a quasi-continuous stream. As stated above, the electromagnetic waves, produced by oscillation of the various electrons traversing the device, add incoherently. There will be partial destruction since positive and negative amplitudes add algebraically. The emitted amplitude is proportional to the square root of the number of electrons in the packet, i.e. to so that the radiation intensity will be proportional to Ng. 

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