Combining Infrared Refraction and Attenuated Total Reflection Spectroscopy

We have specified and obtained a ZnSe prism with an unconventional face angle cut to 30°. This prism, with internal incidence angles ranging from 30° to 48°, allows users to record internal reflection spectra below the critical angle and attenuated total reflection (ATR) spectra above the critical angle without the need to change optics or move or replace the sample. We demonstrate its capabilities using 102 spectra of benzyl benzoate taken with s- and p-polarization at different angles of incidence. The subcritical spectra were analyzed to obtain n_∞, a key parameter for correcting the ATR spectra. These corrected spectra were subsequently used to determine the complex refractive index for all ATR measurements. The averaged complex refractive index function shows excellent agreement with that obtained through ATR spectroscopic ellipsometry.