Time-resolved photoluminescence study of AgCl:Cd²⁺ crystalline foils: excitation energy transfer

Crystalline AgCl:Cd²⁺ thin foils (Cd²⁺ concentration 62.5-5000 ppm) were studied by time-resolved photoluminescence spectroscopy in the temperature range 20-80 K using a mechanical phosphoroscope. It has been found that the emission spectrum consists of two bands, located at approximately 480 nm (blue) and approximately 590 nm ('red'). With increasing delay after excitation (3-100 ms), the emission spectrum shifts considerably to the red region. Similarly, a temperature increase at fixed delay results in a red-shifted spectrum. To explain these results, a simple kinetic model is suggested supporting the existence of two radiative channels (i) self-trapped exciton and (ii) a nearby Cd²⁺ emission centre. A simple method is presented for how to use the photoluminescence behaviour to check the suitability of AgCl:Cd²⁺ foils to record high-energy-particle tracks.