Thin film IR and computational studies of liquid di-n-butylether

► The complex refractive index of liquid di-n-butylether 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 vibrational analysis based on anharmonic B2PLYP/N07D calculations was performed. ► Several conformers of di-n-butylether were taken into consideration to obtain high accuracy of modelled IR spectrum. ► Identification of numerous bands in the MIR range was possible.