A new model for thermoluminescence (TL) kinetics is presented, which is a natural generalization of the standard localized transition model. The model of semi-localized transitions (SLTs) allows trapped charge carriers to be excited to the conduction band. Analytic equations for SLTs are constructed using an enumeration technique which transforms concentrations of carriers to concentrations of states of localized trap-recombination centre pairs. Solving numerically the set of equations, we demonstrate some basic features of the SLT model. It is shown that SLT is able to produce so-called TL displacement peaks that were previously found in one-dimensional TL simulations.
Influence of lithium tetraborate (Li2B4O7, TBL) glass matrix on the luminescent properties of the Pr+3 ions emission was investigated. It was demonstrated that the decrease of matrix long-range ordering leads to substantial widening of corresponding peaks in the emission spectra in comparison with crystalline Ca4GdO(BO3)3 matrices. During the decrease of temperature from 292 down to 82K a distinct low-energy spectral shift of the principal red luminescent band from 607to610nm is observed, which is a consequence of a coexistence of several structural borate fragments. Simulations of incorporation the Pr3+ ions into the TBL glasslike matrix were carried out using the Langevin molecular dynamics simulations and quantum chemical simulations. Possibility of partial substitution of boron ions by Pr3+ ions is demonstrated. The contribution of the electron-phonon subsystems to the spectral broadening of the corresponding emission red lines was evaluated. It was shown that the main contribution to the emission bands gives harmonic electron-phonon interactions contrary to the generally adopted model assuming prevailing role of anharmonic electron-phonon interactions.
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