Photoacoustic spectroscopy

Photoacoustic spectroscopy is the measurement of the effect of absorbed electromagnetic energy (particularly of light) on matter by means of acoustic detection.

The discovery of the photoacoustic effect dates to 1880 when Alexander Graham Bell showed that thin discs emitted sound when exposed to a beam of sunlight that was rapidly interrupted with a rotating slotted disk.

The absorbed energy from the light causes local heating, generating a thermal expansion which creates a pressure wave or sound.

[citation needed] By using cantilever enhanced photoacoustic spectroscopy sensitivity can still be further improved enabling reliable monitoring of gases on ppb-level.

These measurements provided crucial data bearing on the problem of ozone depletion by man-made nitric oxide emission.

In the last twenty years, very low cost instruments for applications such as leakage detection and for the control of carbon dioxide concentration have been developed and commercialized.