Springer Science & Business Media, Apr 10, 2010 - Science - 185 pages
There is a growing need in both industrial and academic research to obtain accurate quantitative results from continuous wave (CW) electron paramagnetic resonance (EPR) experiments. This book describes various sample-related, instrument-related and software-related aspects of obtaining quantitative results from EPR expe- ments. Some speci?c items to be discussed include: selection of a reference standard, resonator considerations (Q, B ,B ), power saturation, sample position- 1 m ing, and ?nally, the blending of all the factors together to provide a calculation model for obtaining an accurate spin concentration of a sample. This book might, at ?rst glance, appear to be a step back from some of the more advanced pulsed methods discussed in recent EPR texts, but actually quantitative “routine CW EPR” is a challenging technique, and requires a thorough understa- ing of the spectrometer and the spin system. Quantitation of CW EPR can be subdivided into two main categories: (1) intensity and (2) magnetic ?eld/mic- wave frequency measurement. Intensity is important for spin counting. Both re- tive intensity quantitation of EPR samples and their absolute spin concentration of samples are often of interest. This information is important for kinetics, mechanism elucidation, and commercial applications where EPR serves as a detection system for free radicals produced in an industrial process. It is also important for the study of magnetic properties. Magnetic ?eld/microwave frequency is important for g and nuclear hyper?ne coupling measurements that re?ect the electronic structure of the radicals or metal ions.
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Chapter 2 Why Should Measurements Be Quantitative?
Chapter 3 Important Principles for Quantitative EPR
Chapter 4 A More in Depth Look at the EPR Signal Response
Chapter 5 Practical Advice About Crucial Parameters
Chapter 6 A Deeper Look at B1B1 and Modulation Field Distribution in a Resonator
Chapter 7 Resonator Q
Chapter 8 Filling Factor
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1/f noise absorption signal absorption spectrum accurate Acquisition software ampliﬁer Appendix baseline broadened Bruker calculation calibration cavity resonator constant critically coupled cryostat crystal detector CW EPR data points deﬁned Demodulated Dewar dielectric difﬁcult double integration DPPH Eaton and Eaton effect electron spin energy EPR absorption EPR line EPR signal EPR spectrometer EPR spectrum example ﬁeld scan ﬁlling factor ﬁltered ﬁrst derivative ﬂow free radical g ¼ g-factor hyperﬁne splitting increases kHz modulation line shape line width linear magnetic ﬁeld magnetic ﬁeld modulation measurement microwave frequency microwave power Mn(II Modulated Signal modulation amplitude modulation frequency nitroxide number of spins obtained optimal output parameters peak peak-to-peak phase sensitive detection power levels power saturation curve pulse quantitative EPR ratio reﬂected power relaxation resonator Q sample tube signal amplitude signal channel signal intensity signiﬁcant solvent species speciﬁc spectra spin trap sufﬁciently TE102 cavity Tempol transition values weak pitch X-band Xepr Yordanov