Dipolar absorption

ColvinVL, Cunningham K L and Alivisatos A P 1994 Electric field modulation studies of optical absorption in CdSe nanocrystals dipolar character of the excited state J. Chem. Phys. 101 7122... 

Scheme 30) (6). Infrared spectra of the products possess a normal amide carbonyl absorption, indicating that the products are not present on the dipolar form (30) but rather as the neutral A -thiazoline tautomer (31 or 32) (6). 

The dielectric permittivity as a function of frequency may show resonance behavior in the case of gas molecules as studied in microwave spectroscopy (25) or more likely relaxation phenomena in soUds associated with the dissipative processes of polarization of molecules, be they nonpolar, dipolar, etc. There are exceptional circumstances of ferromagnetic resonance, electron magnetic resonance, or nmr. In most microwave treatments, the power dissipation or absorption process is described phenomenologically by equation 5, whatever the detailed molecular processes. 

Dispersion mode A Lorentzian line shape that arises from a phase-sensitive detector (which is 90 out of phase with one that gives a pure-absorption-mode line). Dispersion-mode signals are dipolar in shape and produce long tails. They are not readily integrable, and we need to avoid them in a 2D spectrum. 

In this Section we want to present one of the fingerprints of noble-metal cluster formation, that is the development of a well-defined absorption band in the visible or near UV spectrum which is called the surface plasma resonance (SPR) absorption. SPR is typical of s-type metals like noble and alkali metals and it is due to a collective excitation of the delocalized conduction electrons confined within the cluster volume [15]. The theory developed by G. Mie in 1908 [22], for spherical non-interacting nanoparticles of radius R embedded in a non-absorbing medium with dielectric constant s i (i.e. with a refractive index n = Sm ) gives the extinction cross-section a(o),R) in the dipolar approximation as ... 

The absorption bands for both quinoid and dipolar structures have been calculated by the PPP method.2,12 The calculations for a more simplified model of the colored form of some spirobenzopyrans using the normal parameters are shown in Table 2.12 In this case, the spiro carbon in the indoline moiety is ignored in the 7i-electron system, and the quinoid structure is assumed. 

Beverina L, Fu J, Leclercq A, Zojer E, Pacher P, Barlow S, Van Stryland EW, Hagan DJ, Bredas JL, Marder SR (2005) Two-photon absorption at telecommunications wavelengths in a dipolar chromophore with a pyrrole auxiliary donor and thiazole auxiliary acceptor. J Am Chem Soc 127 7282-7283... 

NMR of solids usually give broad featureless absorptions due to the dipolar interactions which, at least in the case of protons, are orders of magnitude larger than the characteristic chemical shifts and spin-spin couplings used for structure elucidation... 

This effect induces a free induction decay (FID) signal in the detection circuit. The FID can be measured, and the normal absorption spectrum can be obtained by means of an inverse Fourier transform. A variety of experimental extensions have been developed for this approach. By means of particular pulse sequences it is possible to detect spin resonances selectively on the basis of a broad ensemble of properties such as spatial proximity and dipolar coupling strengths. The central fundamental quantity of interest is, however, still the energy spectrum of the nuclear spin,... 

Water absorption can also cause significant changes in the permittivity and must be considered when describing dielectric behavior. Water, with a dielectric constant of 78 at 25°C, can easily impact the dielectric properties at relatively low absorptions owing to the dipolar polarizability contribution. However, the electronic polarizability is actually lower than solid state polymers. The index of refraction at 25°C for pure water is 1.33, which, applying Maxwell s relationship, yields a dielectric constant of 1.76. Therefore, water absorption may actually act to decrease the dielectric constant at optical frequencies. This is an area that will be explored with future experiments involving water absorption and index measurements. 

F(ABA) = 0.95, LnICj, = -3.79 x 10-2 Ex + 1.86 (Rg = 0.971) ) see figure 4. Finally, even in highly polar solvents like TFE where the model exists exclusively in the keto-form, the same copolymer has an enolcontent of about 16 % and,moreover, it shows an important specific absorption band at A 380 nm which may be tentatively attributed to new dipolar structures such as ... 

Finally, it should be mentioned that Raman and infrared absorption spectra (i.e., absorption spectra among vibrational levels) are very often complementary methods with which to investigate the energy-level structure associated with vibrations. If a vibration (phonon) causes a change in the dipolar moment of the system, which occurs when the symmetry of the charge density distribution is changed, then the vibration... 

A giant dipolar resonance (GDR) exists in the majority of photoabsorption and photonuclear reactions. This resonance energy corresponds to the fundamental frequency for absorption of electric dipole radiation by the nucleus acting as a whole. It can be envisioned as an oscillation of neutrons against the protons in a nucleus. The GDR occurs at energies of 20-24 MeV in light material and of 13-15 MeV in heavy nuclei. A compendium of the GDR parameters is found in Ref [3]. 

In the case of dipolar produced line width, a rigorous expression for the second moment (Equation 17) of the resonance absorption line allows one to obtain quantitative structural information (Section II,B and C). The... 

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