NO2 Photodissociation Yields Oxygen Species

The photodissociation of nitrogen dioxide ($NO_{2}$) involves the breaking of a chemical bond in the molecule using light energy (photons).

Photodissociation Reaction

When $NO_{2}$ absorbs ultraviolet (UV) radiation, it can break apart. The primary photodissociation pathway yields nitric oxide ($NO$) and an oxygen atom ($O$). The reaction is typically represented as:

$ NO_{2} + h\nu \rightarrow NO + O $

Identifying the Oxygen Species

The oxygen atom ($O$) produced can exist in different energy states. Photodissociation of $NO_{2}$ predominantly produces the oxygen atom in its ground electronic state, which is the triplet state denoted as $O(^{3}P)$.

• $O(^{3}P)$: This represents the ground electronic state of the oxygen atom. It is the most stable and commonly formed state in this reaction under typical atmospheric conditions.
• $O(^{1}D)$: This is an electronically excited state of the oxygen atom. While possible under specific high-energy conditions or from other molecules (like $O_3$ or $N_2O$), it is not the primary product of $NO_2$ photodissociation.
• $O^{+}$ and $O^{-}$: These are ions of oxygen atoms (cation and anion, respectively). Photodissociation of neutral $NO_{2}$ does not primarily produce these ionic species.

Therefore, the photodissociation of $NO_{2}$ primarily yields the ground state oxygen atom, $O(^{3}P)$.