- Laser-induced fluorescence
:"For other uses, see
Laser-induced fluorescence (LIF) is a spectroscopic method used for studying structure of molecules, detection of selective species and flow visualization and measurements.
The species to be examined is excited with help of a
laser. The wavelengthis often selected to be the one at which the species has its largest cross section. The excited species will after some time, usually in the order of few nanoseconds to microseconds, de-excite and emit light at a wavelength larger than the excitation wavelength. This light, fluorescence, is measured.
Two different kinds of spectra exist, disperse spectra and excitation spectra.
The disperse spectra are performed with a fixed lasing wavelength, as above and the fluorescence spectrum is analyzed. Excitation scans on the other hand collect fluorescent light at a fixed emission wavelength or range of wavelengths. Instead the lasing wavelength is changed.
An advantage over
absorption spectroscopyis that it is possible to get two- and three-dimensional images since fluorescencetakes place in all directions (i.e. the fluorescence signal is isotropic). The signal-to-noise ratioof the fluorescence signal is very high, providing a good sensitivity to the process. It is also possible to distinguish between more species, since the lasing wavelength can be tuned to a particular excitation of a given species which is not shared by other species.
LIF is useful in the study of the electronic structure of molecules and their interactions. It has also been successfully applied for quantitative measurement of concentrations in fields like
combustion, plasma, spray and flow phenomena (such as Molecular tagging velocimetry), in some cases visualizing concentrations down to nanomolar levels.
* detection of purity cite web
last = Takeyuki
first = Tanaka "et al."
title = The Application of Laser Induced Fluorescence Spectroscopy to Measurement of Purity Level in Textiles
publisher = Jido Seigyo Rengo Koenkai
url = http://sciencelinks.jp/j-east/article/200605/000020060506A0129627.php
accessdate = 11 October
accessyear = 2008 ]
Planar laser-induced fluorescence
* [http://aol.wff.nasa.gov/index.php?&MMN_position=2:2 THE NASA Airborne Oceanographic Lidar ]
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