VERY HIGH-FREQUENCY EPR-94 GHZ INSTRUMENT AND APPLICATIONS TO PRIMARYREACTION CENTERS FROM PHOTOSYNTHETIC RED BACTERIA AND TO OTHER DISORDERED-SYSTEMS

There are many advantages to carrying out electron paramagnetic resona nce experiments at very high frequencies, either as part of a multifre quency strategy for solving problems or for special characteristics of high frequencies. These special characteristics include the potential for high point sensitivity, enhanced resolution, separation of simila r species. altered sensitivity to motion, suppression of motional effe cts, and many others. This paper describes a three-millimeter-waveleng th (W-band, 94 GHz) EPR spectrometer built for a multi-user facility a nd illustrates with some examples, most of them being disordered syste ms. One significant example is the oxidized primary reaction center, P 865+, isolated from the red photosynthetic bacteria Rhodobacter Sphaer oides R-26. The W-band technique applied to both centers isolated from bacteria grown from either deuterated or ordinary growth media allows extraction of the full g anisotropy in these centers and sets the sta ge for multifrequency EPR spectroscopy to yield a full analysis of the various contributions to linewidths in these systems.