Resonance like effect

For the second harmonic generation, we find that above a certain input intensity a dynamics reminiscent of a competitive, multi-wave mixing process occurs the pump field is mostly reflected, revealing a novel type of optical limiting behavior, while forward a nd b ackward g eneration i s g enerally b alanced. W e a Iso s tudy t he case of parametric down-conversion, where an intense second harmonic signal is injected in order to control a much weaker fundamental beam. Our results reveal the onset of a new process that has no counterpart in bulk materials both transmission and reflection display an unexpected, unusual, resonance-like effect as functions of input second harmonic power. 

The resonance-mediated coupling mechanisms described above involve subtle quantal intramolecular/intermolecular donor-acceptor effects that tend to be inadequately described by current-generation empirical potentials. Simulations based on these potentials are therefore likely to be inherently defective for describing realistic folding processes in proteins. However, approximations such as those illustrated in Example 5.8 may ultimately make it feasible to incorporate additional resonance-mediated effects into empirical force fields of tractable form. 

When an electromagnetic wave interacts with resonators, the effect of quantization of all possible stationary stable oscillating amplitudes arises without the requirement of any specifically organized conditions (like the inhomogeneous action of external harmonic force). 

R-type para substituents lead to large increases in the rates of thermolysis of azidobenzenes.44 hi nitrobenzene at 120 °C the rates follow the Hammett-type relationship log A = —5.44 — 2.33indicating conjugative stabilization of a nitrene-like transition state. + R-type ortAo-substituents cause even larger rate increases, suggesting a special resonance proximity effect (34). 

Degani, H., M. Gochin, SJ.D. Karlish, and Y. Shechter. 1981. Electron paramagnetic resonance studies and insulin-like effects of vanadium in rat adipocytes. Biochemistry 20 5795-9. 

Resonance-like suppression of the higher harmonics in the response spectrum of a superparamagnetic particle is investigated. Using a nonperturbative approach, we analyze the steady processes that take place under arbitrary values of the DC (bias) and AC (excitation) strengths. The results show that the suppression effect is equally achieved on varying either noise (temperature) or force (external field intensity) or by a combination of both. In the fundamental aspect, we surmise... 

There is an intrinsic experimental problem when using magnetic field modulation in ESR spectroscopy that is associated with spurious resonance-like modulations transferred to the microwave carrier and arising from modulations of the resonator microwave characteristics. This phenomenon, perhaps apocryphally, was called potato by F. Bloch because of the resemblance when the effect is displayed as a lissajous figure. 

Chemical Enhancement Compared to electromagnetic enhancement, aspects of the contribution of chemical enhancement [27-29], are less known. Chemical enhancement has other synonyms such as charge transfer (CT) and the short-range effect. It is associated with the electronic structure (state) of the metal and the adsorbate, which can be explained by a resonance-like Raman mechanism (vide infra). As most of the electrochemical SERS systems involve the formation of strong or weak chemical bonds for the adsorbate with the electrode surface, it is... 

The innate reactivity of the parent ring is determined by the inductive and resonance electronic effects of the heteroatom(s) present in the ring. Therefore, C—H fimctionahzation via an aromatic electrophilic substitution pathway most likely takes place at the C2 (and C5) position of Iff-pyrroles, furans, and thiophenes (Figure 3). 

Chemical enhancement is typically explained by the CT mechanism. When a molecule is adsorbed on a metal surface, new electronic states are formed due to chemisorption. The new electronic states may serve as resonant intermediate states in Raman scattering. If the Fermi level of the metal is located between the Highest Occupied Molecular Orbital (HOMO) Lowest Unoccupied Molecular Orbital (LUMO) in energy, CT excitations may likely occur at lower energy than intrinsic intramolecular excitations of the adsorbate [55-58]. According to Albrechts notation [55], in the CT mechanism via Albrechts A term Franck-Condon term) only the totally symmetric modes are resonantly enhanced when the laser excitation is close to an allowed electronic transition, and only one excited state is involved. The resonance Raman effects for vibrational modes that are non-totally symmetric, are usually observed when these modes couple two excited states of the chromophore. The product of the symmetry of both excited states should be equal or contain the non-totally symmetry. This mechanism is known as the Herzberg-Teller mechanism or B mechanism in Albrechts notation. 

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