The absorption of light energy by molecules leads to chemical reactions and photochemical transformations through a process called electronic excitation. When a molecule absorbs light energy, it gets excited and moves from its ground state to a higher energy state, known as the excited state. This change in energy levels can cause the molecule to undergo various chemical reactions and transformations.In the excited state, the molecule may undergo several processes, such as:1. Dissipation of energy: The molecule can lose its excess energy by emitting light fluorescence or phosphorescence or by transferring energy to other molecules collisional quenching .2. Photochemical reactions: The excited molecule can undergo chemical reactions with other molecules, leading to the formation of new products. These reactions are called photochemical reactions.3. Photodissociation: The excited molecule can break apart into smaller fragments, a process known as photodissociation or photolysis.4. Intersystem crossing: The molecule can change its electronic state, leading to different chemical reactivity.Environmental factors such as temperature and pressure can significantly affect photochemical reactions:1. Temperature: An increase in temperature can increase the rate of photochemical reactions by providing more energy to the reacting molecules. Higher temperatures can also increase the number of molecules in the excited state, leading to more reactions. However, very high temperatures can also lead to the deactivation of excited molecules, reducing the overall reaction rate.2. Pressure: Changes in pressure can affect the rate of photochemical reactions by altering the concentration of reactants and the frequency of collisions between molecules. Higher pressure can increase the rate of collisional quenching, which can reduce the overall reaction rate. On the other hand, lower pressure can decrease the rate of collisional quenching, leading to more efficient photochemical reactions.In summary, the absorption of light energy by molecules leads to electronic excitation, which can result in various chemical reactions and photochemical transformations. Environmental factors such as temperature and pressure can significantly influence the rate and efficiency of these reactions.