photo-ionization, the interaction of electromagnetic radiation with matter resulting in the dissociation of that matter into electrically charged particles. The simplest example, the photoelectric effect, occurs when light shines on a piece of metal, causing the ejection of electrons. Another category of photo-ionization involves the disruption of covalent chemical bonds, producing positively and negatively charged fragments; such a reaction is often called the primary process of a photochemical reaction. http://www.britannica.com/EBchecked/topic/457697/photo-ionization
(physical chemistry) The removal of one or more electrons from an atom or molecule by absorption of a photon of visible or ultraviolet light. Also known as atomic photoelectric effect. http://www.answers.com/topic/photoionization
See Also
15.14 - Dissociation Liberates Spontaneous Energy
Atomic Clusters
Dissociation
Part 15 - Dissociating Water
Thermosphere
photodissociation