Transient infrared emission spectroscopy
Conventional infrared emission spectroscopy has normally been applied only to optically thin samples because of the phenomenon of self-absorption. In an optically thick material, self-absorption severely alters the emission so that the resulting spectrum closely resembles a black-body emission spectrum. Spectral features characteristic of the material are very weak and grossly altered in appearance, making the spectrum analytically of little use. Transient infrared emission spectroscopy (TIRES) produces useful emission spectra from optically thick samples by greatly reducing self-absorption. In TIRES a laser beam is used to rapidly heat the sample surface creating a transient hot layer. A spectrometer collects the emission from this layer before it cools and thickens by thermal diffusion. The layer is optically thin at infrared wavelengths, and so self-absorption is reduced. If a pulsed laser is used, the desired thin layer will exist at the laser spot on the sample surface for a short time immediately after the laser pulse,so the emission collection must be synchronized with the laser firing. If a continuous-wave (CW) laser is used, the sample must move through the beam or the beam must move over the sample surface. The transient layer will then exist along the beam path on the sample surface immediately behind the beam position, and thus the emission observation must be spatially correlated with the laser beam, but no synchronization is needed. Results using both types of lasers will be discussed.
- Research Organization:
- Iowa State Univ. of Science and Technology, Ames, IA (USA)
- Sponsoring Organization:
- DOE/ER
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 6615193
- Report Number(s):
- IS-M-636; CONF-890754-2; ON: DE90017253
- Resource Relation:
- Conference: 6. international topical meeting on photoacoustic and photothermal phenomena, Baltimore, MD (USA), 31 Jul - 3 Aug 1989
- Country of Publication:
- United States
- Language:
- English
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