The Photochemistry of Sunscreens.
To understand how sunscreens work, one must understand how molecules interact with light energy. Absorption of light by a molecule is associated with the part of its structure called a chromophore, which may or may not encompass the whole molecule. For organic molecules the chromophores that are responsible for the absorption of ultraviolet light are generally associated with delocalised p-electrons in conjugated systems.
Once
in the excited state the molecule has several different pathways that it can
take:
The
molecule can emit a photon and return to its ground state.
The molecule can return to its ground state by emitting the energy thermally through a series of vibrational transitions.
The molecule can undergo some type of reaction from the excited state, which is generally termed photochemistry.
Finally, the molecule can convert to a lower energy state.The favored path will be the one which is most rapid.
Click here for information on SPF Level.