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FT-IR PAS methods offer unique capabilities that allow analysis of a very wide range of sample types in the near- and mid-IR spectral regions. Samples with either homogeneous or depth varying compositions can be analyzed, in the latter case with higher depth resolution and depth range than is available by other IR sampling techniques. As recent and future advances in instrumentation and data analysis are put into wider use, FT-IR PAS is expected to play an increasingly important role in molecular spectroscopy particularly with layered and gradient materials.
The authors thank Andreas Mandelis for providing the theoretical
equations used to calculate the date in Figure 18, David Drapcho for information
on impulse PAS, and Robert Meglen for the wood samples and chemometric results
shown in Figures 20-23. This work
was supported by MTEC Photoacoustics, Inc., Bio-Rad Laboratories, and the Ames
Laboratory, which is operated for the USDOE by Iowa State University under
contract No. W-7405-ENG-82.
DSP
Digital
Signal Processing
LED
Light Emitting Diode
OPD Optical Path Difference
PET
Poly(ethylene terrephthalate)
PMMA
Poly(methyl methacrylate)
TIRS
Transient
Infrared Spectroscopy
TRS
Time-resolved Spectroscopy