Gas Phase Reactions#
Ion-Molecule Reactions#
These are reactions between ions and neutral molecules. They are typically fast and important in the cold, dense regions of space where ionization can occur due to cosmic rays or ultraviolet (UV) radiation.
- Example:
\[
\text{H}_3^+ + \text{CO} \rightarrow \text{HCO}^+ + \text{H}_2
\]
Neutral-Neutral Reactions#
These are reactions between two neutral species. They generally require higher temperatures to overcome activation energy barriers but can occur in regions with sufficient kinetic energy or through tunneling.
- Example:
\[
\text{O} + \text{OH} \rightarrow \text{O}_2 + \text{H}
\]
Radiative Association Reactions#
These occur when two atoms or molecules collide and form a stable molecule by emitting a photon to carry away excess energy.
- Example:
\[
\text{C} + \text{O} \rightarrow \text{CO} + h\nu
\]