In this work we report on the absorption spectra of ethanol and water in the region 430-700 nm using a homemade halogen lamp-based photothermal lens spectrophotometer with a multipass probe-beam configuration. The spectra also include well resolved, higher absorption overtones. The instrument achieves high sensitivity due to multiple reflections within the optical cavity containing the sample. Finally, an Arduino board was used for collecting and digitizing the signal, thus enabling a more compact device.
Keywords: TLS; Thermal lens spectrometry; absorption of ethanol; absorption of water; vibration overtones.