AI Article Synopsis
- The study observes EPR (Electron Paramagnetic Resonance) spectra showing spin exchange frequencies greater than the hyperfine separation, a phenomenon predicted 50 years ago but not previously identified.
- When the frequency ratio ω/ < 1, the spectra reveal two normal spin modes with distinct absorption components, while for ω/ > 1, one spin mode becomes negative (emissive).
- The results align with theoretical predictions, indicating that the intensity of the first-derivative spectra remains constant, and the spin exchange rate is continuous at the critical frequency ratio.
Article Abstract
We report the experimental observation of an EPR spectral manifestation of spin exchange frequencies, ω, larger than the N hyperfine separation, , predicted 50 years ago but previously not observed. For spectra with ω/ < 1, where γ is the gyromagnetic ratio of the electron, the spectrum consists of two "normal" spin modes each with one absorption and one dispersion component separated by < . decreases with ω. In stark contrast, when ω/ > 1, the spectrum consists of two absorption spin modes, one of which is negative (emissive). We show that the experimental behavior of the spin modes agrees with theory: (a) the doubly integrated intensity of the first-derivative spectra remains constant because the increased intensity of the positive spin mode minus the negative emissive mode remains constant; (b) the value of the spin exchange rate constant = ω/, where is the molar concentration, is continuous through ω/ = 1.
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| http://dx.doi.org/10.1021/acs.jpclett.4c00157 | DOI Listing |
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