Magic-Angle Sample Spinning Electron Paramagnetic Resonance—Instrumentation, Performance, and Limitations

Fast right-angle spinning EPR on organic radicals: Resolution enhancement and angle determination

“…All experiments were performed on a Bruker ESP 380E spectrometer at frequencies of about 9.4 GHz and a temperature of 205 K. The homebuilt probehead for fast rotation at variable angles has been described elsewhere [14]. The angle between the rotation axis and the static field was generally 90°, except for the experiment (see Fig.…”

“…AR EPR provides information on the relative orientation of interaction tensors; however, with rotation frequencies below I kHz reorientation effects are too small for organic radicals with their much smaller anisotropies of the magnetic interactions. We have recently introduced MAS EPR with rotation frequencies up to 17 kHz, which yields isotropic EPR spectra for species with anisotropies below 20 MHz and is thus complementary to the RAS experiments [13,14]. Nevertheless, most organic radicals are accessible to neither of the two techniques because they feature anisotropies well above 10 MHz and not much higher than 100 MHz, which are too large for the MAS EPR experiment and too small for slow RAS.…”

Evaluation and Comparison of Pulsed and Continuous Wave Radiofrequency Electron Paramagnetic Resonance Techniques for in Vivo Detection and Imaging of Free Radicals

“…It has been shown that when the excitation bandwidth ν (given by γ B 1 ) is not comparable to the spectral bandwidth f , destructive interference between contributions of spins with similar resonance offsets can suppress the signal intensity (29). The phase dispersion of the magnetization that is excited off resonance becomes very significant, resulting in substantial sensitivity loss when the spectral bandwidth exceeds the excitation bandwidth by a factor of 5 or more.…”

“…This growth occurs during the recovery of the preamplifier. Besides limiting the sensitivity of the spectrometer, the dead time may lead to considerable distortion in the spectral features, if the resulting truncated FID is Fourier transformed without any phase correction (28,29). Several phase correction procedures are routinely used in NMR spectroscopy (30).…”

Radio frequency continuous‐wave and time‐domain EPR imaging and Overhauser‐enhanced magnetic resonance imaging of small animals: instrumental developments and comparison of relative merits for functional imaging

“…If the excitation bandwidth is not adequate to cover the spectral band width, then destructive interference between contributions of spins with similar resonance offsets can suppress the signal intensity. 119 Increasing the RF power can increase excitation bandwidth. The RF power P o available at the resonator is given by:…”