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Study of photosynthesis using thermoluminescence (TL) requires precise control of the experimental parameters, particularly the excitation source and the sample temperature. In this paper, we describe the design of an instrument that allows automatic control of various steps of the experiment and present illustrative results to demonstrate its versatility. The temperature sequence, the range and the rate of cooling and heating of the sample can be set and controlled anywhere between −150 and +90 • C. The sample temperature can also be held constant at any temperature in this range to within ±2 • C. Five light emitting diodes, covering discrete wavelengths from 470 to 660 nm and white light, are used for pulsed or continuous excitation. The ultra-high sensitivity and versatility of this instrument enabled two significant observations to be made, being reported for the first time in this paper, namely that (a) TL occurs in photosynthetic and non-photosynthetic materials even without pre-excitation and (b) TL also occurs during the sample cooling phase.

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