Using phase in FTIR photoacoustic spectrometry
- Iowa State Univ., Ames, IA (United States)
FTIR spectrometers with phase modulation capabilities make the phase of a photoacoustic signal much more accessible than previously, because all wavelengths are modulated synchronously. The commercial advent of such spectrometers has therefore heightened interest in using photoacoustic phase in depth profiling. The phase delay of the signal increases as the depth at which absorption occurs within a sample increases. The phase behavior in structured samples will be examined. In simple cases, the ordering, identity and thickness of layers in a discretely layered sample can be straightforwardly determined from the phase shifts among spectrum peaks. Complications arise in more complex cases, some of which will be discussed. In principle, the same approach may be used with rapid-scan FTIR spectrometers, but the application is much more difficult since modulation of different wavelengths is no longer synchronous. In addition, background signals interfere with determining phase at the higher rapid scan velocities. Nevertheless, when possible, using phase with rapid scan spectra can assist in depth profiling and reduce saturation in spectra. Examples will be discussed.
- OSTI ID:
- 191686
- Report Number(s):
- CONF-941098-; TRN: 95:006733-0042
- Resource Relation:
- Conference: FACSS XXI: 21st annual conference of the Federation of Analytical Chemistry and Spectroscopy Societies (FACSS), St. Louis, MO (United States), 2-7 Oct 1994; Other Information: PBD: 1994; Related Information: Is Part Of 21st annual conference of the Federation of Analytical Chemistry and Spectroscopy Societies; PB: 257 p.
- Country of Publication:
- United States
- Language:
- English
Similar Records
Phase reference materials for photoacoustic spectroscopy
Hadamard transform photoacoustic spectrometry and depth profiling