The absorption of light by molecules in photocatalytic processes has a significant impact on their electronic structure and reactivity. When a molecule absorbs a photon of light, it gains energy, which causes an electron to be promoted from its ground state to an excited state. This process is known as electronic excitation, and it results in the formation of an excited-state molecule with a different electronic configuration than the ground-state molecule.The excited-state molecule has a higher energy level and is generally more reactive than the ground-state molecule. This increased reactivity is due to the presence of an unpaired electron in a higher energy orbital, which makes the molecule more susceptible to chemical reactions. In photocatalytic processes, the excited-state molecule can undergo various reactions, such as electron transfer, energy transfer, or bond cleavage, leading to the formation of reactive intermediates, such as radicals, ions, or excited-state molecules of different species.These reactive intermediates can then participate in a series of chemical reactions, ultimately leading to the formation of the desired products. The overall photocatalytic process can be divided into three main steps: light absorption, generation of reactive intermediates, and the subsequent chemical reactions involving these intermediates.In summary, the absorption of light by molecules in photocatalytic processes affects their electronic structure by promoting electrons to higher energy levels, resulting in the formation of excited-state molecules. These excited-state molecules have increased reactivity, which allows them to participate in various chemical reactions, ultimately leading to the formation of the desired products.