Parallel mode EPR spectroscopy

Multifrequency EPR Study of High Spin Cr(III) and the Analysis of Allowed and Forbidden Transitions using Perpendicular and Parallel Mode EPR Spectroscopy. 

During oxidation of the MoFe protein the P clusters are the first to be oxidized at about -340 mV. This redox potential was first measured (40) using Mossbauer spectroscopy and exhibited a Nemst curve consistent with a two-electron oxidation process. It is possibly low enough for this redox process to be involved in enzyme turnover (see Section V). No additional EPR signal was observed from this oxidized form at this time. However, later a weak signal near g = 12 was detected and was finally confirmed, using parallel mode EPR... 

An open volume, high isolation RF system suitable for pulsed NMR and EPR spectrometers with reduced dead time has been described. It comprises a set of three RF surface coils disposed with mutually parallel RF fields and a double-channel receiver (RX). Theoretical and experimental results obtained with a prototype operating at about 100 MHz have been reported. Each surface RF coil (diameter 5.5 cm) was tuned to 100.00 0.01 MHz when isolated. Because of the mutual coupling and the geometry of the RF coils, only two resonances at 97.94 MHz and 101.85 MHz were observed. These were associated with two different RF field spatial distributions. In continuous mode operation the isolation between the TX coil and one of the RX coils (singlechannel) was about —10 dB. By setting the double-channel RF assembly in subtraction mode the isolation values were optimised to about —75 dB. The described system was selected as a model for potential applications in solid-state NMR and in free radical EPR spectroscopy and imaging. 

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