The splitting of a molecule by a photon.
WRCC Climate and Weather Terms Glossary

A chemical reaction involving sunlight in which molecules are split into their constituent atoms. Also known as photolysis.
NASA Earth Observatory

Photodissociation - This is a specific type of photolysis reaction, in which the destruction of a molecule is initiated strictly by solar energy.
[The Astrophysical Journal; v.334; p.771; 1988.]
[The Journal of Physical Chemistry; v.98; p.1369; 1994.] 
Atmospheric Chemistry Glossary