Surface infrared spectroscopy using a dual-channel polarization-modulation spectrometer

Matthew J. Smith; Robert Dueval; Robert M. Corn

doi:10.1117/12.56368

1 March 1992 Surface infrared spectroscopy using a dual-channel polarization-modulation spectrometer

Matthew J. Smith, Robert Dueval, Robert M. Corn

Proceedings Volume 1575, 8th Intl Conf on Fourier Transform Spectroscopy; (1992) https://doi.org/10.1117/12.56368
Event: Eighth International Conference on Fourier Transform Spectroscopy, 1991, Lubeck-Travemunde, Germany

Abstract

The sensitivity of an FT-IR spectrometer for measuring monolayers and other thin films can be enhanced if one takes advantage of the surface selection rule to reduce the dynamic range of the experiment. This is accomplished in polarization modulation infrared reflection-absorption (PM-IRRAS) by rapid modulation (74 KHz) of the linear polarization of the incident light , and subsequent demodulation of the detector signal. PM-IRRAS yields a differential signal which contains only the surface information. This differential signal is usually ratioed against the total reflectance signal to yield the spectrum of interest. Normally, two sequential measurements are required. First, the differential signal is acquired, then the total reflectance measurement is made. However, a better method is to use the dual channel approach first described by Buffeteau, et. al.1 The principal advantage of this method is that all isotropic (i.e. atmospheric and nonsurface) absorptions are perfectly ratioed.

Citation Download Citation

Matthew J. Smith, Robert Dueval, and Robert M. Corn "Surface infrared spectroscopy using a dual-channel polarization-modulation spectrometer", Proc. SPIE 1575, 8th Intl Conf on Fourier Transform Spectroscopy, (1 March 1992); https://doi.org/10.1117/12.56368

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