Electron Paramagnetic Resonance Spectroscopy
Electron Paramagnetic Resonance (EPR), and the related phenomenon, Electron Spin Resonance (ESR), provide information on electronic structure in a variety of systems. In addition to structural information, EPR/ESR can also be used to study dynamics in fluid systems. Timescales for studies of dynamics are typically on the order of nanoseconds to microseconds, due to the size of the relevant magnetic moments. This is a very interesting range for fundamental biological processes and motivates many EPR studies in biophysical applications. In contrast, the relevant timescales for NMR are typically much slower. Thus NMR and EPR can provide complementary information on dynamics in complex systems.
In order to take full advantage of the sensitivity to structure and dynamics that EPR can offer, it is often necessary to obtain spectra over a broad range of EPR frequencies, as spectra obtained at different frequencies are sensitive to different processes in general. Thus, unraveling the dynamic and structural information in the EPR spectrum requires sophisticated instrumentation and theoretical analysis. For high field work, the Earle group uses quasioptical techniques to generate and process the EPR signal for subsequent data analysis. Quasioptical techniques complement standard waveguide techniques that are common in EPR spectroscopy below 95 GHz. Spectrometers in the lab cover the range 9 -- 240 GHz with a planned extension downwards in frequency to 2 GHz. The lineshape theory necessary for analyzing the EPR spectra is implemented in a suite of spectral simulation and fitting routines, mostly developed in the laboratory of Jack Freed at Cornell University, and extended to incorporate recent advances in maximum entropy methods of data analysis developed at the University at Albany.
The Earle group has opportunities for students with interests in experimental and theoretical technique development.