COMMISSION ON MOLECULAR STRUCTURE AND SPECTROSCOPY
(I.5)
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
Objective:
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.
Progress:
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.