Optical constants of liquid pyrrole in the infrared

► The complex refractive index of liquid pyrrole in the MIR and NIR range was determined. ► In the MIR region very thin layers with thicknesses of a few micrometers had to be used to obtain reliable data. ► The theoretical studies involved an evaluation of a few computational methods used for the spectra modelling process. ► The vibrational analysis based on anharmonic B2PLYP/N07D calculations was found to be most effective. ► Identification of numerous bands in the MIR range was possible.