Rotation sweep spectroscopy

The recently introduced rotation sweep spectroscopy [11] is based on the realization that decreased rotor size provides acceleration proportional to the inverse cube of the rotor diameter... 

Unlike correlation spectroscopy based on spin diffusion, the adiabatic version enables, in principle, almost full exchange of magnetization between the two spins. As a result, the entire signal intensity will reside in the cross-peaks. Violation of the adiabaticity is characterized by the appearance of a diagonal peak and can be expected to occur if the rotation sweep is too fast compared to the interaction between spins. While numerical simulations indicate possible linear dependencies of the polarization transfer coefficient on spin coupling and the rate of the sweep over a range of practical values, the validity of this assumption remains to be tested. Here we present a semi-quantitative example of a relayed polarization transfer process. 

The most common techniques for testing electrodes are sweep voltammetry, galvanostatic poten-tiometry, rotating disk electrochemistry, and impedance spectroscopy. Detailed information about these techniques may be found in most classical electrochemical textbooks [6-13], and we will present here the basics of these techniques. 

To perform broadband FTMW spectroscopy we require a microwave source that can produce phase-locked linear frequency sweeps over an 11 GHz frequency range in times ranging from 100 ns to 1 ps (sweep rates of 10 ° - lO" MHz/s). The short sweep durations are required so that the sample is polarized on a time scale faster than the pure dephasing of the rotational free indnction decay (FID). Traditional microwave synthesized sweepers are typically limited to sweep rates of about 10 MHz/s. We have developed a microwave source based on a 4 Gs/s arbitrary waveform generator that can produce the required excitation pulses. A schematic of the microwave source is shown in Figure 1. 

Methanol oxidation on CNF- and CNT-supported Pt-Ru particles in liquid electrolytes has been studied using cyclic voltammetry, chronoamperometry [13,231-237], and electrochemical impedance spectroscopy [236]. Rotating disk electrode and linear potential sweep voltammetry in liquid electrolytes were used to study the oxygen reduction reaction on Pt supported on CNTs and CNFs (see,... 

Since a fuel cell is an electrochemical device, electrochemical mefliods are deemed to play important roles in characterizing and evaluating the cell and its components such as the electrode, the membrane, and the catalyst. The most popular eleetroehemical characterization methods include potential step, potential sweep, potential cycling, rotating disk electrode, rotating ring-disk eleetrode, and impedance spectroscopy. Some techniques derived from these methods are also used for fuel cell characterization. 

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