Dipoles resonance

A third technique for field enhancement is the dual-dipole effect. In this case, two resonant particles are brought close enough together to interact with each other. In the gap region between the two particles, the field can become much more intense than that from either 

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Nuclear science in particular obtains from laser-driven electron sources a brand new input to perform interesting measurements in the context of many laboratories equipped with ultrashort powerful lasers. The ultrashort duration of these particle bunches represent a further attractive feature for these kinds of studies. In the following, we will focus on nuclear reaction induced by gamma radiation produced by bremsstrahlung of laser-produced electrons in suitable radiator targets. This way is usually mentioned as photo-activation and is particularly efficient for photons of energy close to the Giant Dipole Resonance of many nuclei. 

Giant dipole resonance. Isovector giant resonances contain information about the SE through the restoring force. In particular the excitation of the isovector giant dipole resonance (GDR) with isoscalar probes has been used to extract A R/R [32], In the distorted wave Bom approximation optical model analysis of the cross section the neutron and proton transition densities are needed as an input. For example, in the Goldhaber-Teller picture these are... 

DIPHTHERIA TOXIN DIPOLAR BOND DIPOLE-DIPOLE INTERACTION NONCOVALENT INTERACTLONS Dipole-dipole resonance energy transfer, FLUORESCENCE... 

In the 1950s, many basic nuclear properties and phenomena were qualitatively understood in terms of single-particle and/or collective degrees of freedom. A hot topic was the study of collective excitations of nuclei such as giant dipole resonance or shape vibrations, and the state-of-the-art method was the nuclear shell model plus random phase approximation (RPA). With improved experimental precision and theoretical ambitions in the 1960s, the nuclear many-body problem was born. The importance of the ground-state correlations for the transition amplitudes to excited states was recognized. 

This bump is called the giant dipole resonance (GDR). Goldhaber and Teller (1948) provided a model for this reaction in which the giant dipole resonance is... 

An excited molecule X can pass into the basic level again. This can be performed by radiation—i.e., by emission of the energy difference as a photon hvx—or by nonradiation by internal quenching where the energy difference is dissipated as thermal energy. Furthermore there is the possibility that the excitation energy is not dissipated by radiation but by interaction with a guest molecule Y. This interaction can be described by diffusion of excitons and/or dipole-dipole resonance. 

Dimole absorption and emission, 247 Dioxetane formation, 253 Donor-acceptor energy levels, 201 property, energies of, 289 Dipole-dipole resonance energy transfer, 192, 193... 

Characteristic Lengths Associated with Dipole-Dipole Resonant S-P Excitation Transfer (pi = d2/flv)... 

In the case of a solid inclusion, the dipole resonance frequency is generally lower than the monopole resonance frequency. For low shear modulus material with dense particles, Chaban finds the dipole resonance frequency... 

Recently we have calculated this term when the shear rigidity of the matrix material is taken into account. We find the dipole resonance frequency... 

One finds that solid inclusions tend to define the low frequency structure in k, the attenuation edge and the resonance in c, by means of the dipole resonance, whereas cavities tend to define it by means of the monopole resonance (35). Since the dipole resonance of a solid inclusion involves center of mass motion of the inclusion, this resonance tends to be at lower frequencies than that due to the monopole of a cavity which merely involves cavity wall motion. The heavier the inclusions in the case of solid inclusion and the softer the matrix material in the case of cavities, the lower in frequency in which significant attenuation is achieved (attenuation edge) and the larger the corresponding scattering cross sections. 

Figure 1 shows an example 30 percent lead inclusions (a = 2mm) in epoxy, Epon 828Z, Here 0 —0 and a is seen to be essentially due to Ops at low frequencies. The volume concentration of inclusions in this example is, however, known to be rather high for Equation (29) to yield exact predictions. It has been pointed out that Equation (31) does not predict the shift in resonance frequency with concentration that is experimentally observed for Pb in epoxy at volume concentrations above 5 percent. Note the steep rise of of and the attenuation edge (predicted by Equation (30) at all concentrations of inclusions), approaching the characteristic (Rayleigh) dependence of Opg below the dipole resonance frequency Equation (26), At ka>l, attenuation is controlled by high frequency resonances above the quadrupole resonance. 

Soft matrix materials do not support shear waves and consequently dipole scattering by solid inclusions and mode conversion effects are weak in such materials. The corresponding resonance frequency is given by Equation (19), Mode conversion is also weak in the case of cavities in soft materials. The dipole resonance frequency is given by Equation (28), In the case of cavities in soft materials, monopole scattering predominates at low frequencies. The lowest resonance frequency is given by Equation (18) and a reduces to... 

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