Instrumentation and Experimental Setup

Instrumentation aspects of ESR spectroscopy are treated thoroughly in a standard text (Poole 1997). However, a majority of ESR users are nowadays concerned with application work rather than development of instrumentation and methods. For such work, a comprehensive knowledge of instrumentation aspects is not required, yet a basic knowledge is needed to measure high-quality spectra and notice problems with hardware. The present chapter intends to present just this basic knowledge and to relate it to proper procedures for experimental setup. It complements Poole’s book, and where more detailed descriptions are needed, they can probably be found there. For pulsed ESR and ENDOR, selected original papers on instrumentation are cited to take modern developments into account. High-field ESR beyond frequencies of 95 GHz, where no fully fledged commercial spectrometers exist, is not included here. This reflects my lack of experience rather than a judgment on the usefulness of higher frequencies for work on biological membranes and membrane proteins. Note also that I discuss instrumentation and setup procedures with particular emphasis on measuring spectra of nitroxide spin probes and spin labels, although it should not be too difficult to adapt the procedures to work on transition metal centers.