What are the steps of fluorescence spectroscopy?

Fluorescence spectroscopy is a three-step process. In order, the steps are excitation, excited-state lifetime, and fluorescence emission. During excitation, energy is provided to the fluorophore through a light source. Then, photons excite the fluorophore after it has been absorbed, creating what is known as an electronic singlet state. After the excitation phase is completed, the molecules stay in an excited state, usually between 1 and 10 nanoseconds, which is known as their excited-state lifetime. Fluorescence emission is triggered by  dispersed energy that was given to the fluorophore in the excitation stage. Every molecule that becomes excited does not return to their normal state. These procedures can then be analyzed for things such as identifying the interactions and matter within a substance. The fluorescence quantum yield is the ratio of the number of fluorescence photons emitted to the number of photons absorbed and is the way of measuring how these processes happen. The last step happens after the energy exits the molecules, and the fluorophore returns to its ground state. The release of energy causes the fluorescent emission to occur, and it can be seen as a longer wavelength than was seen at the time of excitation. This is because the photon has lost an amount of energy. The time it takes the fluorophore to emit varies on its interactions with the environment. The difference between the initial wavelength and the emitted one is called the Stokes shift. A fluorophore can be used several times, excited repeatedly and used for analysis, as well as in various tests.