Tunable Diode Laser Absorption Spectroscopy

Tunable Diode Laser Absorption Spectroscopy ( TDLAS, English to German as " absorption spectroscopy using tunable laser diodes ") is a method by which measured an absorption the concentration or density of the gas under investigation or gas component ( for example, methane or water vapor) is determined. As a source of radiation used is a laser diode, and therefore the TDLAS is counted to the method of laser spectroscopy.

The absorption takes place in lines that are caused by transitions between different energy states of an atom or molecule. If the wavelength used the laser radiation in the optical range, as these are usually transitions between different electronic energy states. When working with infrared radiation, so the absorption usually occurs between different vibration -rotation states of a molecule.

The radiation is generated in the TDLAS with tunable laser diode, whose emission frequency can be varied by varying the current through the diode laser or by means of its temperature.

In addition to the determination of a density from the measured absorbance of a line indicative of the pressure and temperature of the gas can be withdrawn from the profile of the line.

The TDLAS is now used application in the study of particle densities in plasmas, in environmental engineering ( determination of pollutant concentrations) and in determining the composition of the Earth's atmosphere.