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Physical Chemistry Division (I)


Number: 150/25/98

Title: Quantities, Terminology and Symbols in Photothermal and Related Spectroscopies

Coordinator(s): Noboru Hirota and M. Terazima

Remarks: Coordinators are consulting with A. C. Boccara (France), A. Mandelis (Canada), A. C. Boccara (France), A. Mandelis (Canada), S. E. Braslavsky (Germany), H. Coufal (USA), G. J. Diebold (USA), S. E. Bialkowski (USA), T. Sawada (Japan), R. Niessner (Germany).

Completion Date: 2004 - Project completed

Photothermal and Related Spectroscopies follow the absorption of light by monitoring the heat produced in the sample by the light. They are very useful for obtaining energetic and kinetic information about reactive species and excited molecules in a wide dynamic range with high sensitivity. The heat produced changes the volume and the refractive index of the sample, and these changes can be detected in several ways. Photoacoustic spectroscopy detects the heat by measuring the sound wave produced by the thermal expansion; this method can be traced to Bell's discovery in 1880 that light absorption generates sound, but it really became active in 1971 when it became possible to detect sound with adequate sensitivity. The detection of the additional infrared radiation created by the heating is a second way of detecting the heat change. The methods of thermal lens, thermal grating, and interferometry, detect the heat through the change in the refractive index of the sample. These last methods were discovered in the 1960s, so all photothermal methods are relatively new. Nevertheless, they are used already in many different areas of science, both pure and applied. It is, therefore, timely to seek international agreement about, and codification of, the classification of the different phenomena, the terms and symbols used to describe the different phenomena, and agreement about the precise processes involved in the different phenomena.

The first draft of the report of this project was completed in 1999 and copies were sent out recently to eight of the leading workers in the field for review and suggestions.

A final document is submitted to public review comments until 31 July 2002.
> see provisional recommendations

The draft contains the following material:

1. Introduction
2. Origins of photothermal effects
3. Glossary of terms
3.1 Grating spectroscopy
3.2 Lens spectroscopy
3.3 Light-induced acoustic spectroscopy
3.4 Photothermal radiometry
3.5 Photothermal calorimetry
3.6 Photothermal interferometry
3.7 Photothermal deflection
3.8 Photothermal reflection change
3.9 Related methods
4. Glossary of related terms
5. Symbols for physical parameters in photothermal effects
6. Cumulative alphabetical list.

project completed - IUPAC Recommendations published in Pure Appl. Chem. 76(6), 1083-1118, 2004


Last update: 28 July 2004


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