Power spectrum broadening

Complications with intensity or spectral analysis sometimes hamper LDE experiments. For small particles with large diffusion coefficients, or for particles with low electrophoretic velocities, the decay constant T becomes large compared to q 1 it [Eq. (92)]. As a result, the power spectrum broadens, making it... 

Fig. 8. The 195Pt-NMR spectra of a DMF solution of [Pt2(en)3(PRI)2(N02) (N03)](N03)2 0.5 H20 (11) at 5°C, acquired on a Bruker WM-250 spectrometer operating at 53.6 MHz. (a) Power spectrum of the Fourier transform of a 1 K FID accumulated with a 5-jjls pulse width, 100-kHz spectral width, and 2000 K transients, (b and c) Normal Fourier transforms of 1 K FIDs accumulated with 10-fis pulsewidths, 42-kHz spectral width, and 64 K transients per spectrum. All FIDs were treated with 400-Hz line broadening functions to suppress noise (58).

Photon Correlation. Particles suspended in a fluid undergo Brownian motion due to collisions with the liquid molecules. This random motion results in scattering and Doppler broadening of the frequency of the scattered light. Experimentally, it is more accurate to measure the autocorrelation function in the time domain than measuring the power spectrum in the frequency domain. The normalized electric field autocorrelation function g(t) for a suspension of monodisperse particles or droplets is given by ... 

Two other technical issues must be discussed briefly. In deducing the viscoelastic parameters through the dispersion equation from the power spectrum of SLS, it must be corrected for the instrumental broadening. The other... 

Theoretically, ESR lines should be infinitely narrow, experimentally, they are broadened by various mechanisms, both intrinsic (determined by sample properties and the physics of the resonance experiment) and extrinsic (dependent on spectrometer operating conditions) Line shapes of ESR signals of peroxy radicals in lignin are often asymmetric because of the solid-state or power spectrum effects of the vanous anisotropic interactions... 

Mu-substituted hexadienyl radicals are easily observed by high-field tS Rotation and their reaction with benzoquinone has been studied. The method is principally the same as in the Mu relaxation kinetics but, since Mu-substituted tmlicals are measured, the disappearance rate of MuO H is determined from the line broadening of the Fourier transformation power spectrum. The obtained value is kjj = 2.8 x 10 M- s- . It is important to note tlmt the reaction rate constant of Mu-substituted radicals may not differ much from that of the H-counterparts. The isotope effect should be small since the mass of Mu- and H-radicals are not much different, and since the reaction center is arated from the site of Mu- and H-addition. 

In general, the intensity of an ESR spectrum increases with an increase in the microwave power R When the applied power level is sufficiently low, thermal relaxation processes can, to a good approximation, maintain the Boltzmann equilibrium between spin levels. When the power level exceeds that amount, the ESR spectrum broadens and its intensity begins to decrease and eventually disappears. This phenomenon is called the power saturation or saturation broadening effect and depends... 

Figure 5 Power spectrum analysis of the Langevin dynamics simulation of the model system. Frequency peaks are in qualitative agreement with constant-energy simulations but somewhat broadened when compared with the data shown in Figure 2.

A qualitatively new result appears in the opposite limit when broadening is adiabatic (Atc 1). In this case only the resolved spectrum is worthy of discussion but in the vicinity of P and R lines the broadening is almost the same as before (Fig. 4.5). The significant changes are on the periphery of both resonances. The far wings of the spectrum do not follow the power law but instead, for

Fig. 5. Effective g assignment of the low-field S = IEPR signals in D. vulgaris Fepr protein [from 11)]. The spectrum was recorded at the optimEd temperature of 12 K, that is, at which the amplitude is maximal and lifetime broadening is not significEmt. EPR conditions microwave frequency, 9.33 GHz microwave power, 80 mW modulation amplitude, 0.8 mT.

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