Ceramics-Silikáty 14, (3) 197 - 213 (1970)

According to G. P. Smith the concentration changes of colour centers in photochromic silver halide glasses may be expressed by the following linear differential equation: dC/dτ = k_dI_dA - (k_fI_f + k_t) C. As apparent from the given equation, the changes of colour center concentration with time are influenced by two basic factors; the formation and the destruction of colour centers, one of which always predominates. The equilibrium between the formation and the destruction of colour center is dynamic. The activated state represents a higher level of energy; once the process of activation is over, a transition to a lower energy level occurs due to relaxation; this represents a return to the original state. Colour center formation is caused by short-wave and near ultraviolet radiation effects; colour center destruction is caused by longwave visible and infrared radiation and by thermal effects. However, a certain part of the visible radiation spectrum does not affect either the formation or the destruction of colour centers. The linear differential equation was solved both for the formation and for the destruction of colour centers. The process of formation may be expressed by the following equation: T - T_s1 = (T₀ – T_s1) e^-(k_fI_f^-+ k_t)τ and the process of colour center destruction by the equation: T_s2 - T = (T_s2 – T_s1) e^-(k_fI_f^-+ k_t)τ