Laser-induced fluorescence (LIF) - Principle

It is a spectroscopic method. The sample is excited with a laser at a wavelength selected with respect to the species to be detected or analyzed. After a few nano or microseconds, the excited species will relaxe by emitting light at a wavelength larger than the excitation one. This fluorescence light can be measured (relaxation time and/or spectral). Excitation mode is also used, fluorescent light is measured at a fixed emission wavelength range during a scan of the excitation wavelength.

Advantages of the method:

• two- and three-dimensional images (fluorescence emission is isotropic).
• very high signal-to-noise ratio  (good sensitivity to the process)
• selectivity (lasing or excitation wavelength)

LIF - Applications

• Structural analysis  of molecules
• Detection of selective species and flow visualization
• Measurement of concentrations
• Detection of tumors
• Pollutants monitoring