Dipole absorption

Considering an electric dipole absorption process, which is in agreement with the oscillator strength / = 0.6, we can use Equation (5.22) to estimate IV, the concentration of absorbing F centers ... 

Conjugated Dipole absorption-A specific type of dipole absorption represented by a structural resonance related to the conjugated backbone of a molecule and characterized by isotropic absorption in the visual spectmm. 

Resonant absorption-A specific type of conjugate dipole absorption associated with two auxochromes separated by a conjugated chain of carbon atoms characterized by absorption in the visual spectrum. The resonance is due to the low velocity of charge transport along the molecule. As a result, the effective wavelength of the molecule is equal to that of the incident photons. The absorption is... 

In complex molecules, such as the Rhodonines, it is important to recognize that both the dipole molecular and resonance molecular absorption can coexist. It is only resonance absorption is functionally important in vision. The spectral absorption associated with both may be observed in the laboratory. However, the dipole absorption is normally only observed in the liquid crystalline state. The mechanics of the resonant molecular process will be detailed in Section 5.4.3. 

Table II. Activation Energies of the Dipole Absorption Process ( 1 Kcal)...

For example, most prototype devices use polymethyl methacrylate CPMMA, trade name PLEXIGLASS) as a substrate material. PMMA has an index of refraction of about 1,49, This produces an escape probability of 26% for isotropic absorption and emission, and an escape probability of 29% for dipole absorption and emission of perpendicularly incident light. 

Linear response theory (TDLDA) applied to the jellium model follows the Mie result, but only in a qualitative way the dipole absorption cross sections of spherical alkali clusters usually exhibit a dominant peak, which exausts some 75-90% of the dipole sum rule and is red-shifted by 10-20% with respect to the Mie formula (see Fig. 7). The centroid of the strength distribution tends towards the Mie resonance in the limit of a macroscopic metal sphere. Its red-shift in finite clusters is a quantum mechanical finite-size effect, which is closely related to the spill-out of the electrons beyond the jellium edge. Some 10-25% of the... 

The magnitude of the observed cross sections, in themselves, is good evidence that the photonuclear effect is mainly an electric dipole effect. Levinger and Bethe have calculated the electric quadrupole effect and conclude that it can only amount to a few percent of the electric dipole effect. If the giant resonance itself is identified with the electric dipole absorption, some of the photonuclear cross section which corresponds to the tails of this resonance can be ascribed to electric quadrupole absorption. In 0 the absorption for x-rays between I3 and iqMev is accounted for satisfactorily by electric quadrupole absorption. 

In general, therefore, a in (4.1) is a tensor, the exact form of which depends upon the orientation of the dipole and the dipole absorption and emission characteristics. The molecule s motion, its interaction with its neighbors, and the decay... 

The i f f) contribution gives rise to the familiar electric dipole absorption responsible for a large part of electronic spectroscopy. The second term in the matrix element may be divided into a symmetric part, identifiable with the electric quadrupole interaction, and an antisymmetric part which is the magnetic dipole operator ... 

In the gas phase or in isotropic hosts, such as liquids, polymers or glasses, the transition dipole moments of the guest molecules exhibit random orientations. In anisotropic systems, like crystals and stretched polymer films, there is usually a correlation between the orientation of the molecule and the geometry of the host matrix. The probability of electric dipole absorption depends on the square of the scalar product... 

Assuming electrie dipole absorption, (i2o) may be ealculated from knowledge of the initial... 

As we have seen there now exist significant measurements of PNC in four different atoms, carried out on five distinct magnetic-dipole absorption lines. In Table 3 we show the most recent result of each experiment together with the value predicted by the Weinberg-Salam weak interaction theory. The predicted values come from atomic calculations "" taking into account the major corrections to the central field approximation. We also show the values of Q defined in Eqs. (9) and (10) that may be inferred in each case from the experimental result and the atomic calculations. 

We saw earlier that the probability of electric dipole absorption is related to the transition dipole moment. However, there are a variety of terms commonly used to describe the strength or probability of absorption. The allowedness or forbiddenness of the transition, and oscillator strength, /, are useful ideas where the relative, rather than absolute value, of the strength of coupling is required. These terms are factors used to describe how likely absorption is by reference to the ideal oscillator of a free electron where the transition is fully allowed and both the allowedness and oscillator strength are unity. 

While the dipole absorption features [114, 124] and photodissociation dynamics of small sodium clusters are rather well known [112, 113, 126, 127, 407-409], there is very little knowledge about potassium clusters larger than the dimer. The lack of experimental data might be caused by ultrafast fragmentation processes within the potassium clusters, so that conventional stationary spectroscopic techniques might fail. Hence, the goal of this section is to determine the photodissociation probability of small potassium clusters as a function of cluster size as well as excitation energy. 

J.M.M. Roco, A. Calvo Hernandez, S. Velasco, Far-infrared permanent and induced dipole absorption of diatomic molecules in rare-gas fluids. I. Spectral theory. J. Chem. Phys. 103 (21), 9161-9174 (1995)... 

A large part of the QM/MM applications to photoinduced processes are focused on the calculations of stationary properties, namely transition energies and dipoles, absorption/emission and electronic circular dichroism spectra, etc. 

For excited states 2 is chosen so that Rjjj + Q is the appropriate LS-coupled Hartree-Fock potential. As an example, consider argon 3p6 Is. Dipole absorption of a photon leads to final states 3p (ks or kd)lp. The usual 3p k P Hartree-Fock potential results by setting... 

The temperature, voltage, frequency, and duration of exposure to moisture have an influence on the electrical properties. For example, the a-c characteristics of water (2) are illustrated in Figures 43 and 44. At low frequencies, the loss (Fig. 43) appears to be ionic. A dipole absorption peak appears at very high frequencies. The ionic loss is increased by a dissolved ionizable salt, but the dipole peak seems to be unaffected. The dielectric constant of water (Fig. 44) is very high until a sudden decrease takes place around the absorption peak just above IQio Hz. 

For dipole absorption of radiation, the selection rules for J are as follows, along with their general designations ... 

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