Fluorimetry
Fluorescence is used to study the properties, structures, identities, and trace analysis of molecules in different samples and in different solutions. Fluorescence is simply the light that molecules give off when they've been excited or when they've gone to an excited electronic state. Molecules don't stay in these excited states very long, they will lose their energy to return to the ground state. There are various ways to do this. One way is that they can give off heat, which an incandescent light bulb will do a lot of in addition to light. Another way is through the emission of photons or a particles of light. This is fluorescence.
Above is the a part of the Jablonski Diagram. This diagram is often used to describe the process of electron absorption and emission. In order to get fluorescence, you must first undergo absorption. This is done by firing photons at a sample in order to excite the electrons present, sending them into a higher energy state than before. This electron is quickly relaxed through kinetic vibrational energy due to it having slightly higher energy than the initial absorption it experiences. Once relaxed, a photon can then be emitted from the energized state back down to the ground state. This emission is seen as visible light.
Above is an instrument deconstruction of a fluorimeter performed in instrumental analysis. A typical basic design will have 4 main parts. To start, there will have to be a light source in order to generate energy. In an experiment we performed, our light source was a green laser and its exact wavelength was 532 nm. This beam of light would then proceed to hit a sample containing a solution that is expected to fluoresce. In an attempt to gather as much light being emitted by the sample, mirrors and lenses are used to concentrate emission onto a wavelength selector. This could be a diffraction grating, prisms, double slits and so on. Finally, your diffracted light hit a detector to gather fluorescence data from.