J. Gotze et al., High-resolution spectrometric analysis of rare earth elements-activated cathodoluminescence in feldspar minerals, CHEM GEOL, 153(1-4), 1999, pp. 81-91
Cathodoluminescence (CL) investigations of igneous, metamorphic and sedimen
tary feldspars indicate that rare earth elements (REE)-activated CL in feld
spars is more common than previously assumed. Hot-cathode CL microscopy com
bined with high-resolution spectrometric analysis of CL emission allow to d
etect some REE below the detection limits of electron microprobe and proton
-induced X-ray emission analysis (PIXE) and reveal variations in the REE di
stribution within single feldspar crystals. Differently luminescing zones c
an reflect changes during feldspar crystallization and/or element fluctuati
ons during secondary alteration processes which are not discernible using c
onventional polarizing microscopy. The results of the study document Eu2+,
Sm3+, Dy3+, Tb3+, and Nd3+-activated CL in feldspars of different origin. T
he influence of the crystal field on shape and position of REE luminescence
spectra significantly differs for divalent and trivalent REE ions. Whereas
Eu2+ shows a broad band emission (similar to 420 nm) which is influenced b
y the local crystal field, trivalent ions of the rare earth show narrow emi
ssion lines which reflect the transitions between excited state wave functi
ons lying inside closed electronic shells. The positions of these peaks and
the characteristic energies are described for the different REE3+. (C) 199
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