Infrared spectra computer-aided

There are two general approaches for computer-aided identification of infrared spectra of unknown compounds [173,196-199,248-250]. The most common approach uses software designed to identify an unknown spectrum by its similarity to a limited number of reference spectra selected from a general or customized library of reference spectra measured under similar conditions (e.g. vapor phase, solid phase, etc.) Commercial... 

The vibrational states of a molecule are observed experimentally via infrared and Raman spectroscopy. These techniques can help to determine molecular structure and environment. In order to gain such useful information, it is necessary to determine what vibrational motion corresponds to each peak in the spectrum. This assignment can be quite difficult due to the large number of closely spaced peaks possible even in fairly simple molecules. In order to aid in this assignment, many workers use computer simulations to calculate the vibrational frequencies of molecules. This chapter presents a brief description of the various computational techniques available. 

It is unreahstic to attempt the use of the Fourier series or of the Fourier integral transforms without the aid of a computer. In recent years a fast Fourier transform (FFT) algorithm for computers has become widely used. This is particularly useful in certain kinds of chemical instrumentation, specifically nuclear magnetic resonance and infrared absorption spectrometers. In such instruments the experimental observations are obtained directly in the form of a Fourier transform of the desired spectrum a computer that is built into the instrument performs the FFT and yields the spectrum (see Chapter XIX). 

Of the various infrared techniques available, Fourier transform infrared (FTIR) spectroscopy has become the most useful for textile finish analysis. The entire spectrum is recorded simultaneously and scanning is not necessary. In this way, many spectra can be recorded and averaged in a short time. FTIR utilizes a computer interface to store and manipulate the recorded spectra. The spectra can then be easily compared with libraries of standard spectra to aid in the identifica-... 

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