A two-stage thermally-assisted optically stimulated luminescence (TA-OSL)

Abstract

A two-stage thermally-assisted optically stimulated luminescence model is studied. Electrons are thermally and optically raised from the ground state to an excited state and there after they are thermally raised from the excited state to the conduction band. A set of simultaneous differential equations generated from the model was solved numerically using ode 15s MATLAB solver. Three assumed conditions are applied to the model and results from the analytical expressions obtained based on the assumptions were compared with the numerical simulation results. The assumed conditions are : (1) the probability of electron moving from the excited state to ground state ( ) is far greater than thermal excitation of electron from the excited state to conduction band ( ) also stimulation light intensity ( ) is far greater than thermal excitation of electron from the ground state to the excited state ( ), (2) also (3) also . For the first condition, the effective activation energy (Eeff) tends towards the energy of the excited state ( ), and the effective frequency factor is the ratio of the product of frequency factor for the excited state ( ) and to (i.e. ). For the second condition, was the activation energy of the ground state ( ) and , is the frequency factor for thermal excitation from the ground state to the excited state. For the third condition, was the sum of and and but when the stimulating light intensities become very small compared to , then becomes approximately equal to .