What is fluorescence and how does it arise?

[retupmoc]

What is fluorescence and how does it arise?

Is it just a spontneous de-excitation after the electron in the molecule (protein) has been excited. This is a 6 mark question in last years Chemistry-2 exam and i don't really know how to go about answering it. Any suggestions?

 

[Monique]

Fluorescence arises when a molecule absorbs light of a certain frequency, which brings electrons from a ground to an excited state. These excited electrons can fall back to their ground state by the loss of energy. There are several ways by which this energy can be lost, like through vibrational energy. Fluorescent compounds have very rigid structures though, so they are unable to vibrate and the electron returns to the ground state through the emittion of a photon. Some of the energy of the photon will already have been lost, so the wavelength has changed to a longer one.

 

[ravenprp]

Fluorescence is a phenomenon in which a substance absorbs light of a specific wavelength and then emits light of a longer wavelength. This process is known as photoluminescence and it is caused by the absorption of energy by molecules or atoms, leading to their excitation to higher energy levels. When these excited molecules or atoms return to their ground state, they release the absorbed energy in the form of light.

Fluorescence can arise in various substances, including molecules, atoms, and crystals. However, in the context of proteins, fluorescence is commonly observed due to the presence of certain molecular groups called fluorophores. These fluorophores have a unique structure that allows them to absorb and emit light.

The process of fluorescence in proteins can be broken down into three main steps: excitation, relaxation, and emission. First, the protein is excited by absorbing light of a specific wavelength, which causes the electrons in the fluorophore to jump to a higher energy level. This excitation can occur through various mechanisms such as absorption of UV or visible light, or through energy transfer from another excited molecule.

Next, the excited electrons undergo relaxation, where they release some of their energy and return to a lower energy level. This process can happen through various pathways, including internal conversion, intersystem crossing, and vibrational relaxation. The relaxation process is highly dependent on the structure and environment of the fluorophore, and it determines the wavelength of the emitted light.

Finally, the relaxed electrons emit light as they return to their ground state. This emission is typically in the form of fluorescence, where the emitted light has a longer wavelength than the absorbed light. The emitted fluorescence can be detected and measured using specialized instruments, providing valuable information about the structure and dynamics of the protein.

In summary, fluorescence arises in proteins through the absorption of light by fluorophores, followed by relaxation and emission of light. This phenomenon has various applications in fields such as biochemistry, biotechnology, and medical diagnostics, making it an important topic in the study of chemistry and biology.