Bridging external and attenuated total reflection infrared spectroscopies through computational simulations

Abstract This work provides an integrated view of attenuated total reflection (ATR) and external reflection (ER) for advanced undergraduate and postgraduate students beginning their study of infrared spectroscopy. The theoretical framework of reflectance is reviewed, and a computational tool developed using GNU Octave is presented to model ER and ATR spectra. Simulating spectra demonstrates how ER spectra evolve to ATR spectra by modifying relevant parameters. This unified approach offers advanced students a deeper understanding of infrared spectroscopy, enhancing their ability to correctly interpret ATR spectra and avoid common pitfalls. The computational exercises and provided code serve as valuable educational resources for exploring reflectance behaviour under different conditions.