Photodissociation

Photodissociation separates a molecule into fragments after photon absorption. For an isolated parent with a single absorbed photon, conservation of energy givesInternal excitation energies here are relative to the parent and product ground states used to define $D_0$; $E_{\mathrm{recoil}}$ is the total product translational kinetic energy in the parent's centre of mass frame. Measuring one product's kinetic energy is insufficient by itself. For two fragments of masses $m_A,m_B$, conservation of momentum gives $E_{\mathrm{recoil}}=E_A(m_A+m_B)/m_B$ when $A$ is detected. Unknown product excitation can conceal part of the available energy.