Effect of the second coordination sphere on the electron transition energies in ZnS-Mn

The influence of the second coordination sphere on the energy of electron transitions in ZnS-Mn is investigated using the crystal field theory. The obtained perturbation effect is small and may be usually neglected.

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Einfluß der zweiten Koordinationssphäre auf die Energie der Elektronenübergänge in ZnS-Mn (Kurze Mitteilung)

Zusammenfassung Der Einfluß der zweiten Koordinationssphäre auf die Energie der Elektronenübergänge in ZnS-Mn wird mit Hilfe der Kristallfeldtheorie untersucht. Es ergibt sich, daß der Störeffekt klein ist und gewöhnlich vernachlässigt werden kann.

     

Quantum key distribution in an optical fiber at distances of up to 200 km and a bit rate of 180 bit/s

An experimental demonstration of a subcarrier-wave quantum cryptography system with superconducting single-photon detectors (SSPDs) that distributes a secure key in a single-mode fiber at distance of 25 km with a bit rate of 800 kbit/s, a distance of 100 km with a bit rate of 19 kbit/s, and a distance of 200 km with a bit rate of 0.18 kbit/s is described.     

Afterglow of manganese centres in pulse-excited ZnS:Mn

The afterglow of self-activated and manganese centres in ZnS-Mn by excitation with a pulsed nitrogen laser is investigated. Assuming that a time-independent part of the excited “blue” centres returns to the ground state under energy transfer to the “yellow” centres, an equation describing the decay kinetics is derived. The comparison with the experimental data shows satisfactory agreement in the time interval up to 120 μs. A maximum in the afterglow curve arises within this limit.     

Luminescence of Y2O3:Eu and Gd2O3:Eu Depending on Precursor and Activation Temperature

The activation of Y₂O₃, Gd₂O₃and (Y_0.7,Gd_0.3)₂O₃ with Eu³⁺ ions at temperatures lower than 1000 °C is studied using different starting compounds. The activator ions are introduced during the crystallization or precipitation of the precursor. Phosphors prepared from hydroxides and activated at 900 °C exhibit luminescence with high efficiency under 254 nm Hg-line excitation. Strong emission is observed even in samples activated at 700 °C. Luminescence intensity, emission and excitation spectra are compared to these of Y₂O₃:Eu produced by the industry.     

Crystal field theory treatment of S2 ion impurity centres with Oh, D4h, C4v and C2v symmetry in alkali halides

The effect of impurity anions on the electron transitions in alkali halide phosphors has been studied. The energies of electron transitions have been calculated for O_h, D_4h, C_4v and C_2v symmetries in the cases of strong and weak fields. The theoretical model has been shown to agree satisfactorily with experimental data assuming the formation of higher symmetry impurity centres to be more probable.