Multifrequency electron paramagnetic resonance of ultramarine blue

• Published in: Applied magnetic resonance Vol. 21; no. 3-4; pp. 563 - 570
• Main Authors: Eaton, G. R., Eaton, S. S., Stoner, J. W., Quine, R. W., Rinard, G. A., Smirnov, A. I., Weber, R. T., Krzystek, J., Hassan, A. K., Brunel, L. C., Demortier, A.
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer Nature B.V 01-12-2001
• Subjects: Anisotropy; Electron paramagnetic resonance; Low temperature; Room temperature
• ISSN: 0937-9347; 1613-7507
• DOI: 10.1007/BF03162429

Electron paramagnetic resonance spectra of the S3/− radical center in ultramarine blue over a factor of about 2500 in frequency (258 MHz to 670 GHz) reveal a substantially Lorentzian shape, without resolution of g anisotropy. Variable temperature measurements found that the line width is independent of temperature, within experimental uncertainty, up to about 90 K at 9.5 GHz and between ca. 5 K and room temperature at 95 and 217 GHz, as expected for an exchange-narrowed signal. Analysis of the increase in the low-temperature line width as a function of frequency above 9 GHz is consistent with an exchange interaction of about 2· 10−2 K. The line width increases as frequency is decreased from 2.7 GHz to 258 MHz which is attributed to the contribution from nonsecular terms that has been denoted the “10/3” effect.