C. Ditlefsen et Dj. Huntley, OPTICAL-EXCITATION OF TRAPPED CHARGES IN QUARTZ, POTASSIUM FELDSPARS AND MIXED SILICATES - THE DEPENDENCE OF PHOTON ENERGY, Radiation measurements, 23(4), 1994, pp. 675-682
Optical excitation of trapped charges has been studied by stimulating
them with photons of energies from 1.8 to 2.7 eV and measuring the res
ulting luminescence at higher photon energies. The samples studied wer
e quartz, potassium feldspar and fine-grained silicate extracts from n
atural sediments. The initial luminescence intensity and its decay as
the traps are emptied have been used to gain information about the tra
ps contributing to the emission. For the quartz studied the data are w
ell explained by excitation from a single trap. The excitation spectra
for potassium feldspars and mixed silicates show evidence of two diff
erent traps, the deepest of which is seen to give rise to the most lum
inescence. Its optical trap-depth may be more than 2.4 eV while the de
pth of the shallow trap appears to be about 2.1 eV. In nature, the dee
per trap will probably not be well bleached during deposition in all a
queous environments, and for optical dating of water-laid sediments se
lective sampling of the shallow trap photons with energies less than 2
.3 eV for stimulation may prove beneficial.