Orthogonal transformations spectroscopy

Fig. 12. Radiofrequency and gradient pulse sequence for velocity exchange spectroscopy (VEXSY) in which successive PGSE pulse pairs (G, and G2X separated by a delay time t , are applied. For an unambiguous correlation, Gj and Gj are required to be collinear. Note the two orthogonal Fourier domains represented (schematically) by r, and tj- Fourier transformation with respect to the acquisition time leads to a third spectral dimension.

On the other hand, successful identification of bacterial spores has been demonstrated by using Fourier transform infrared photoacoustic and transmission spectroscopy " in conjunction with principal component analysis (PCA) statistical methods. In general, PCA methods are used to reduce and decompose the spectral data into orthogonal components, or factors, which represent the most coimnon variations in all the data. As such, each spectrum in a reference library has an associated score for each factor. These scores can then be used to show clustering of spectra that have common variations, thus forming a basis for group member classification and identification. 

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