photodisociation

Photodissociation is a chemical process where a molecule breaks apart into two or more fragments after absorbing one or more photons. This absorption of light energy excites the molecule to a higher electronic or vibrational state, making the bonds within the molecule weaker and prone to breaking. The energy required for photodissociation is typically in the ultraviolet or visible spectrum of light.

The energy of the absorbed photon must be at least equal to the bond dissociation energy of the molecule for the process to occur. If the absorbed photon has more energy than is required, the excess energy can be distributed among the kinetic energies of the fragments or promote further electronic excitation. The specific wavelengths of light that cause photodissociation are characteristic of the molecule and are often used to identify its presence.

Photodissociation plays a significant role in various natural phenomena and technological applications. In Earth's atmosphere, it is crucial for processes like ozone depletion, where ultraviolet radiation breaks down ozone molecules. It is also important in interstellar chemistry, influencing the formation and destruction of molecules in space. In laboratory settings, photodissociation is utilized in techniques like photochemistry for synthesizing new compounds and in mass spectrometry for analyzing molecular structures. Understanding photodissociation is key to comprehending chemical reactions driven by light.