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Condensed Molecular Materials Seminar

Lecture Title "What can we learn about Spin Systems from EPR and ENDOR at High Frequency?"
Date Friday 13 November 2009 16:30
Lecturer Johan (Hans) van Tol associate scholar scientist at the National High Magnetic　Field Laboratory in Tallahassee, FL.
Place

201 Seminar Room, Main Office Building of IMS
Summary

Electron Paramagnetic Resonance has greatly evolved since the days of impurity centers in minerals. High frequencies have enabled increased resolution, and made possible the study of systems with large zero-field splittings and/or large exchange interactions, while multi-frequency EPR has contributed considerably to the study of dynamics of bio-molecules, in particular spin-labeled proteins. Here we will focus on the implementation of CW and especially Pulsed EPR at frequencies in the 100-400 GHz range, and the possibilities created by high-frequency EPR in the study of a variety of spin systems. E.g. the high resolution enables site- and orientation selective Electron Nuclear Double Resonance. Pulsed techniques furthermore enable the direct measurement of the relaxation parameters and the homogeneous linewidth. The direct single-phonon spin-lattice relaxation (SLR) can be considerably enhanced at high frequencies, and will in general be the dominant relaxation mechanism at low temperatures. A study of the SLR as a function of the frequency thus in principle allows the mapping of the phonon density of states. Secondly, the contribution of the electron-electron dipolar interactions to the spin-spin relaxation can be quenched at low temperatures, allowing the study of quite concentrated spin systems by pulsed EPR. First results of Pulsed EPR in single molecule magnets will be presented.
Contact

Toshikazu Nakamura (IMS)
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