Anomalous Dispersion Effects in the IR-ATR Spectroscopy of Water

• Published in: Applied spectroscopy Vol. 54; no. 1; pp. 138 - 143
• Main Authors: Hancer, Mehmet, Sperline, Roger P., Miller, Jan D.
• Format: Journal Article
• Language: English
• Published: London, England SAGE Publications 01-01-2000
• Subjects: AQUEOUS SOLUTIONS; CONCENTRATION RATIO; EXPERIMENTAL DATA; FOURIER TRANSFORM SPECTROMETERS; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; LIGHT TRANSMISSION; SILICON; SILVER CHLORIDES; SPECTRAL REFLECTANCE; Water; Infrared; Anomalous dispersion (AD); Interface; ATR
• ISSN: 0003-7028; 1943-3530
• DOI: 10.1366/0003702001948222

The distortion of band shapes seen in infrared attenuated total reflection (IR-ATR) spectroscopy of strongly absorbing materials such as water, relative to transmission sampling, is shown here to be due to the anomalous dispersion (AD) of water. This distortion occurs in addition to the normal 1/v dependence, and, contrary to previous reports, is shown to not be due to chemical changes of water at the interface between the optical element and bulk solution. IR-ATR spectra of water were modeled with approximation-free calculations. The modeled spectra are compared with experimental ATR spectra for different internal reflection elements, and the results are discussed in terms of the AD optical effect.