ESR frequency

The first compensating pole will be located at the capacitor s ESR frequency (4,020 Hz). 

Thus the high-frequency ESR is about half the low-frequency ESR. Frequency multipliers should always be used, or we will overestimate the heating and underestimate the life, possibly forcing us to move to a larger capacitor size (overdesign). 

Garcia et al. describe the design of an L-band DNP spectrometer at 40 mT, employing an ESR frequency of 1.1 GHz, and report a coupling factor for 4-oxo-TEMPO dissolved in water of p = 0.39. This coupling factor corresponds to a translational correlation time of r = 150 ps, which implies that the actual coupling factor at 40 mT should be higher to yield... 

The off-diagonal elements depend on the x and y components of the local field, which contain many fluctuating components oscillating at different frequencies. The parts which oscillate at the ESR frequency ( ) induce transition between the a- and P-states. By making a Fourier analysis of V(f) and using time-dependent perturbation theory [22], the transition probability between the a- and p-states (P< ) is given by... 

Clark and co-workers measured the temperature dependence of a DNP experiment and succeeded in obtaining OE and SSE independently as shown in Figure 6.30 [173], indicating a characteristic crossover from pure OE above 150 K to the mixed effect below 150 K. The OE and the SSE can be distinguished by the ESR frequency at which the maximum enhancement would be obtained (and equivalently by the peak-ratio y/x as shown in Figure 6.30) the same frequency as the usual ESR peak for the OE, but at Wp (i) for the SSE. Namely, in the SSE a required energy /i(we w ) for... 

Some very interesting double resonance experiments were carried out on ruby (155-161). A single crystal of ruby at liquid helium temperature was placed in a constant magnetic field and simultaneously subjected to the microwave ESR frequency of the chromium spins and the NMR radiofrequency of either the AP or the Cr (9.54 % abundant) nucleus. The results were as follows. 

To obtain reliable information from ESR studies of metallic nanoparticles, it is necessary to take the skin effect into account. Namely, for the particles smaller than skin depth at ESR frequency (for typical metals it is about 0.5-3 p.m), the additional contribution to the line width has to appear. This contribution originates from scattering of spins by the particle surface, and it is inversely proportional... 

Overlap of signals from different chemical elements is an inherent weakness of ENDOR spectroscopy at conventional ESR frequencies of 9.6 GHz (X band) as can be seen in Fig. 9. To overcome this problem, pulse ENDOR techniques have been developed that separate ENDOR signals according to the nuclear Zeeman frequency or the magnitude of the hyperfine couphng. Provided the hardware is available, high-field ENDOR provides a more simple alternative. At an ESR frequency of 95... 

Electron spin resonance (ESR) spectroscopy has been widely used to obtain information about the molecular dynamics of polymers. The method requires the introduction of a stable free-radical reporter group, such as a nitroxide, into the system. Nitroxide spin labels can be covalently attached to the polymer of interest, and can therefore serve as probes of the local backbone dynamics of the polymer, providing information on the local orientation, stracture, dynamics, and enviromnent. " A commonly used nitroxide is shown in Eig. 1. Depending on the ESR frequency, motion on time scales between 10 and 10 ° s may be investigated by this method, making it ideal to study the dynamics of macromolecules and macromolecular structures or assemblies. 

The curves shown in Fig. 14 were calculated from pirical expressions that can be used to estimate the needed for a given calculation from the ESR frequency and without performing a swept-fields calculation. Although an axial diffusion tensor was assumed in deriving these expressions, the method may also be applied when a rhombic Ry) diffusion tensor is anticipated, using the lesser of the quantities R, Ry. 

The ESR working window in which the ESR line shapes are sensitive to rotational reorientation depends on the anisotropy of the A- and g-tensors of the radical for nitroxides, the range for Xp, is 10 -10 s, which means that the technique is applicable to polymer solutions, polymer gels, and solid polymers at temperatures close to or above Tg. At the X-band ESR frequency ( 9 GHz), the rotational dynamics in most liquids is usually sufficiently fast, that is, Xp,Aco 1 [where Am is a measure of the magnitude of the orientation-dependent part of the spin Hamiltonian ffj(t)] such motions (Xjj < lO s) fall within the motional narrowing (fast-motional) regime. For slower dynamics (Xp,Am > 1), more complicated slow-motional spectra are observed. ... 

In the work of Xiao et al. the resonance of a single electronic spin is observed directly in a field-effect transistor (FET). After creating a paramagnetic trap, they observe the source/drain current in the FET, as a function of the ESR frequency. Under a magnetic field, the Fermi level of the channel electrons is adjusted to lye between the two electronic states of the paramagnetic trap. The idea is that, if only the lower spin state is occupied, then no electron can jump from the channel to the trap. But if only the upper spin... 

Fig. 33, ESR frequency in CuMn versus field in the two limiting cases of large (slope 1) (Monod and Berthier 1980) and M, — Q (Schultz et al. 1980) (M, =

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