chapter  3
72 Pages

Experimental Considerations: Instrumentation and Methodology

WithB. H. Robinson, H. Thomann, A. H. Beth, P. Fajer, L. R. Dalton

The great majority of electron paramagnetic resonance (EPR) experiments performed during the past 20 years have been conducted utilizing commercial X-band EPR spectrometers of one of the two versions. During much of this time, the design of commercial EPR spectrometers has changed little; however, this situation is likely to change dramatically in the next few years. The magnetic field needed to observe EPR is produced by a low impedance electromagnet and current-stabilized magnet power supply. A Hall effect field controller, which is common to all commercial EPR spectrometers, provides a field proportional regulation of the magnetic current supply. The field regulator produces a voltage that is proportional to the magnetic field strength, making use of the Hall voltage from a thermostated Hall probe; the absolute accuracy of the field calibration depends on the linearity of the Hall device. Several workers have devised experimental techniques to circumvent the problem of defining phase angle.