IMPURITY LEVEL LIFETIME MEASUREMENTS USING A LOCK-IN AMPLIFIER

Lifetimes of metastable levels of chromium in ruby are determined usin g an unusual technique. The fluorescence from the chromium is measured using an ac technique in which the excitation is modulated and the fl uorescence is detected synchronously. The novelty lies in the measurem ent of the dependence of the signal on the modulation frequency and ex tracting the lifetime from the frequency dependence. The experiments a nd data analysis demand a detailed understanding of the methods of loc k-in amplification and synchronous detection and hence they can serve as a useful primer on the subject. The observed values for the lifetim es show excellent agreement with previous measurements. (C) 1996 Ameri can Association of Physics Teachers.