A Double-Modulation Fourier Transform Infrared Approach to Studying Adsorbates on Metal Surfaces

Abstract

Polarization modulation has been combined with Fourier transform infrared (FT-IR) spectroscopy to yield a sensitive method for obtaining infrared reflection-absorption spectra of monolayer films adsorbed on low-area metal surfaces. A 10-Å film of cellulose acetate adsorbed on a polished copper coupon was examined and the results compared with spectra obtained on the same instrument without polarization modulation. The signal-to-noise ratio is significantly better with the polarization modulation approach. The new method has the additional advantage of being sensitive only to molecules adsorbed on the surface. IR absorption by background gases is not detected.