(a) EPR spectrum of electron centers formed after UV irradiation of MgO nanocubes. Traces (b) and (c) are simulated spectra of the two color center species F(1) and F(2), respectively.
EPR spectra of electron centers generated by UV irradiation (a) and generated after the reaction of UV preirradiated samples with (b). (c) Difference between spectra (b) and (a). (d) Simulated trace of spectrum (c).
In the course of the homolytic splitting process [Schemes 1(c)–1(e)], one of the H atoms binds to the corner and converts it effectively into a four-coordinated anion. The other H atom is released and adsorbs at certain surface sites to form centers. Discussed configurations of centers are (a) the configuration with adsorbed at a site, (b) configuration with adsorbed at a site, (c) adsorbed at a distant three-coordinated oxygen site , and (d) adsorbed at a distant five-coordinated oxygen site .
Measured -tensor components and hyperfine coupling constants of electron centers on the surface of MgO nanocubes.
H-atom adsorption energies and ionization potentials, excitation energies , and oscillator strengths calculated for different types of centers on MgO surface sites.
Isotropic parts of the hyperfine interaction of unpaired electrons with , , and calculated for different types of centers on MgO surface sites. Notations , , , , , and refer to atoms for each center, as shown in Fig. 3.
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