Zusammenfassung
LiF crystals with F-2(-) centers contain a whole series of F-based colour centers with spectrally overlapping absorption spectra. On the short-wavelength side the absorption spectrum of the F-2(-) centers is overlapping with the absorption spectra of other colour centers and is therefore not directly accessible by transmission measurements. Fluorescence excitation spectroscopy is employed here to ...
Zusammenfassung
LiF crystals with F-2(-) centers contain a whole series of F-based colour centers with spectrally overlapping absorption spectra. On the short-wavelength side the absorption spectrum of the F-2(-) centers is overlapping with the absorption spectra of other colour centers and is therefore not directly accessible by transmission measurements. Fluorescence excitation spectroscopy is employed here to gain information on the absorption spectrum of F-2(-) centers in spectral regions where the absorption by other centers is present. The fluorescence signal emitted beyond 1200 nm is detected as a function of the excitation wavelength in the range from 350 nm to 1100 nm. The F-2(-) center absorption cross-section spectrum in the wavelength range from 690 nm to 1100 nm and from 350 nm to 410 nm is determined from the fluorescence excitation quantum distribution and the transmission spectrum. Influences of fluorescence re-absorption and Forster-type energy transfer on the fluorescence excitation quantum distribution and the subsequent F-2(-) center absorption cross-section determination are discussed.
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