Fourier transform photoacoustic spectrometry

Those areas which have received great attention in Fourier Transform Infrared Spectrometry recently have been the chromatographic infrared spectrometry hybrid systems. This includes gas chromatography-infrared spectrometry and liquid chromatography-infrared spectrometry. Two other areas of current interest are photoacoustic-infrared spectroscopy and the use of infrared spectroscopy to determine impurities in semiconductor materials. 

In Chapters 2 to 8 we describe the theory and instrumentation needed for an appreciation of the way that Fourier transform infrared and Raman spectra are measured today. The sampling techniques for and applications of FT-Raman spectrometry are described in Chapter 18. The remaining chapters cover the techniques and applications of absorption, reflection, emission, and photoacoustic spectrometry in the mid- and near-infrared spectral regions. 

In Chapter 20 we saw how photoacoustic (PA) spectra could be measured with a step-scan interferometer no matter whether the PA signal was demodulated with a lock-in amplifier or by digital signal processing (DSP). For DSP, a Fourier transform (FT) has the same function as the lock-in amplifier. Manning et al. [14] showed that the same approach is feasible in DIRLD spectrometry with a step-scan FT-IR spectrometer but without a PEM. Consider the case where the detector signal contains components caused by simultaneous sinusoidal phase modulation at frequency /pm, and sample modulation at frequency fs. The phase- and sample-modulated components of the signal can be demodulated either with a... 

Photoacoustic spectrometry (PAS) was first developed for applications in the ultraviolet-visible region its practical use for measurements in the mid-infrared region became popular with Fourier transform (FT) spectrometers in the 1980s. 

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