Fluorescence Spectroscopy

This type of spectroscopy analyzes fluorescence as a function of wavelength when the laser is tuned to an electronic absorption of the sample. In general, luminescence involves the emission of electromagnetic radiation by a material after that material has absorbed energy from a light source. Luminescence is described as fluorescence when the time lag between excitation and emission is on the order of 10 nanoseconds. Laser-induced fluorescence (LIF) can be used for a wide array of applications, including the qualitative and quantitative measurements of the concentrations of molecules in a sample and the mapping of energy level diagrams. Fluorescence studies are usually conducted with tunable continuous wave (cw) laser systems; the tunability of organic dye lasers and the use of frequency-doubled Titanium:Sapphire (Ti:S) lasers enhance the experimental capabilities of cw fluorescence measurements. For broadband fluorescence studies of samples in the solid or liquid states, linewidths between 2 and 400 GHz are usually suitable. Fluorescence studies in chemistry, semiconductors or polymers are well-served by cw tunable systems.   For fluorescence spectroscopic experiments in the gas phase, the most important laser parameter may be the linewidth. One of the most important contributions to fluorescence spectroscopy has been the availability of ultrafast lasers capable of picosecond and femtosecond pulses in time-resolved fluorescence measurements.