Electron paramagnetic resonance study of new paramagnetic centers in microcline-perthites from pegmatites

Spectroscopic features of ultrahigh-pressure impact glasses of the Kara astrobleme

“…Structure-analogous signals are often observed in the EPR powder spectra of alkali feldspars and silica with impurities of organic matter. In feldspar spectra, this signal is usually attributed to the ammonia radical 39 NH 3 + , and in the spectra of silica to the methyl radical 40 ∙CH 3 . The value of g-factor and hyperfine splitting of the radicals in the Kara glass spectrum allows attributing them to the ∙NH 3 + radical 41 .…”

“…8B). In mineral matrixes, such as K-feldspars, the ammonia radicals are formed usually from NH 4 + cations under ionizing radiation being stable below 200 °C 39–41 . Precursors (NH 4 + ) of the analyzed ammonia radicals in the Kara crater glasses perhaps were formed by the interaction of nitrogen oxides with organic matter during heating of the target rocks.…”

Characteristics of emission centers in alkali feldspar: A new approach by using cathodoluminescence spectral deconvolution

“…Most natural feldspars do not have enough Cu 2+ and Ga 3+ to emit optically detectable CL (Mariano et al 1973;Matyash et al 1982;Smith and Brown 1988;De St. Jorre and Smith 1988;Jaek et al 1996;Götze et al 2000), which is true in the case of the Balmaceda alkali feldspar. Therefore, the blue emissions of most Balmaceda alkali feldspar should be attributed to Al-O --Al and/or Ti centers referring to the abovementioned previous results.…”

“…Various emission centers have been proposed for blue CL emissions in alkali feldspar: (1) Cu 2+ at the Ca site as a divalent ion concentrated in synthetic and natural feldspars, in which CL can be assigned to a hole-trapped center near a Cu 2+ impurity with an emission band at 420 nm (Mariano et al 1973;Matyash et al 1982;Smith and Brown 1988;Jaek et al 1996); (2) Al-O --Al defect center (oxygen defect associated with Al-O-Al bridge as the Löwenstein bridge) formed with two Al atoms, one of which is structural Al and the other is impurity Al (Marfunin 1979;Finch and Klein 1999;Götze et al 2000;Słaby et al 2008), showing an emission band at 450-480 nm; (3) Ti 4+ incorporated with Al sites as an impurity, the Ti 3+ electron center (Ti 4+ +e -) or oxygen defect associated with Al-O-Ti bridges, exhibiting an emission band at 430-470 nm, but it is not clear whether titanium is an activator or a sensitizer enhancing intrinsic CL spectra (Marfunin and Bershov 1970;Mariano et al 1973;Mariano and Ring 1975;Speit and Lehmann 1976;Kirsh et al 1987;Smith and Brown 1988;Ginibre et al 2004;Lee et al 2007;Parsons et al 2008); (4) Ga 3+ related to an emission band at ~500 nm, but it is uncertain whether it behaves as a CL activator or enhances the formation of lattice defects, in which a minimum concentration is 800 ppm Ga, presumably to trigger the blue-green CL color in albite (De St. Jorre and Smith 1988). Most natural feldspars do not have enough Cu 2+ and Ga 3+ to emit optically detectable CL (Mariano et al 1973;Matyash et al 1982;Smith and Brown 1988;De St. Jorre and Smith 1988;Jaek et al 1996;Götze et al 2000), which is true in the case of the Balmaceda alkali feldspar.…”

Radiation-induced self-structuring of radiative defects complexes in a K-feldspar crystal: A study by thermoluminescence

“…Gaussian intensity distributions have been reasonably reproduced from quantum-mechanic modified configuration coordinate models (Klick and Schulman, 1957 and references therein). It is important to note that in this experiment the glow peak retains the Gaussian profile almost exactly and do not change the position of the maximum with temperature variations between 50 and 200 • C. Based on the wavelength of this emission, that appears in several semi-conducting oxides, and knowing the nature of radiation-induced defects produced in similar specimens (Matyash et al, 1982), the radiative centre can be related to electrons trapped in oxygen vacancies (E centre). Fig.…”