Construction and Demonstration of a Low-Cost Educational Transient Absorption Spectrometer

We describe the construction and use of a low-cost light-emitting diode (LED)-based transient absorption spectrometer. Both the pump and the probe in the instrument are high power LEDs which replace more costly flash lamps or lasers used in prior educational transient absorption systems. Apart from cost, the wide variety of LEDs available means that numerous excitation wavelengths are possible. Our spectrometer operates on the microsecond timescale and records transient spectra, allowing the unambiguous identification of chemical intermediates. We illustrate its functionality by conducting transient absorption experiments to extract dye isomerization kinetics. Furthermore, we demonstrate its use in measuring the triplet excited state kinetics of an organic dye. The system is both affordable and portable, making it an ideal platform for teaching modern pump-probe spectroscopies to undergraduates as well as high-school students. Future upgrades to the LEDs, their drive electronics as well as detectors can increase the instrument’s time resolution and/or sensitivity.