Glasses of the x CuO · (100 - x)[3 B 2 O 3· 0.9 PbO · 0.1 Ag 2 O ] system, with 0.5 ≤ x ≤ 10 mol %, were prepared and investigated by means of electron paramagnetic resonance (EPR) measurements. Structural details of different diamagnetic vitreous systems may be revealed by the Cu 2+ ions, frequently used as paramagnetic probes in EPR experiments. The shape and the intensity of the recorded EPR lines are dependent on the CuO content. The EPR spectra are asymmetric, with characteristics for Cu 2+ (3d9) ions in axially-distorted octahedral symmetric sites. Due to the interaction of the unpaired electron spin (s = 1/2) with the nuclear one (I = 3/2) of Cu 2+ ions, the characteristic hyperfine structure (hfs) is visible for small concentrations of CuO in both spectra bands (parallel and perpendicular). The increasing of copper content in the samples generates the EPR absorption spectra modification, the hfs being resolved in the parallel band of the spectra in whole compositional range, while in the perpendicular band, hfs disappear for x > 3 mol %. This fact indicates the structural modification in Cu 2+ vicinity and possible magnetic interactions.
Intracellular Hypoxia of Tumor Tissue Estimated by Noninvasive Electron Paramagnetic Resonance Oximetry Technique Using Paramagnetic Probes
