Microwave spectral response

For many materials, the simple spectral model gives reasonable estimates of the Hamaker constant when the microwave term is omitted and a single oscillator term is used. An example for a material with a more complex spectral response is water. The original parameterization of Ninham with a microwave term and just one oscillator term for IR and UVeach [23] was improved in several steps to a model including a relaxation term, five IR, and six UV oscillator terms [26, 27]. Two alternative models closer to a full spectral analysis for water have recently been proposed by Dagastine et al. [28] and Fernandez-Varea and Garcia-Molina [29]. 

CW experiments (sometimes called stationary or steady state ) are ones in which either no modulations are used, or they are so low in frequency that no spectral complications ensue. (This is only approximately the case if 100 kHz field modulation is employed. This frequency gives rise to modulation sidebands and, under saturating conditions, rapid passage effects.) Time-domain ESR involves monitoring the spin system response as a function of time. Pulse ESR can be divided into two broad categories the response of spin systems to sequences of microwave pulses (spin echo) and the response of spin systems to step changes in resonance conditions (saturation recovery). 

Afc are different, the temperature dependence of these quantities is identical based on microwave measurements (Zhang et al. 1994). The frequency dependence of (Ti(ft)) is also very similar for the two polarizations. This indicates that die electrod5mamic response of YBa2Cu306 95 is identical along the a- and Z)-directions, except for the additional spectral weight along the a-axis. 

Field splitting of energy levels (see Fig. 2.8) can also be observed in transitions from level 1 or 2 to some third level. As a result, of this sphtting, the spectral line of the 2 —> 3 transition is split into two hnes (Fig. 2.8(b)). This phenomenon was first observed in microwave spectroscopy (the Autler-Townes effect (Autler and Townes 1955)). In the optical region of the spectrum and in the presence of phase relaxation, such a splitting can apparently be observed only if condition (2.62) is satisfied, that is, when the response of the two-level system to the laser-light field is truly oscillatory. 

Simple Spectral Method [23] In the simple spectral method, a model dielectric response function is used. It combines a Debye relaxation term to describe the response at microwave frequencies with a sum of terms of classical form of Lorentz electron dispersion (corresponding to a damped harmonic oscillator model) for the frequencies from IR to UV ... 

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