Photochemistry in Physical Chemistry
- ejcha62
- 11월 14일
- 1분 분량
Photochemistry is a branch of physical chemistry that studies the chemical effects of light. It focuses on how molecules absorb photons and undergo electronic excitation, leading to chemical reactions that would not occur under ordinary thermal conditions.
Key Concepts
Absorption of Light
Molecules can absorb light at specific wavelengths, promoting electrons from a ground state to an excited state.
The energy of the absorbed photon must match the energy difference between the molecular orbitals.
Excited States and Reactivity
Once in an excited state, molecules often have different chemical reactivity compared to their ground state.
Excited molecules may participate in bond breaking, bond formation, energy transfer, or electron transfer reactions.
Photochemical Reactions
Direct photoreactions: Occur when a molecule absorbs light and reacts immediately. Example: the decomposition of silver halides in photography.
Sensitized photoreactions: Occur when a molecule absorbs light and transfers energy to another molecule, inducing a reaction. Example: photosynthesis in plants.
Quantum Yield
Measures the efficiency of a photochemical reaction. It is defined as the number of molecules reacting per photon absorbed.
Quantum yield provides insight into the mechanisms and pathways of photochemical processes.
Applications
Environmental chemistry: Photodegradation of pollutants under sunlight.
Biochemistry: DNA damage and repair caused by UV light.
Material science: Photopolymerization in 3D printing and photochemical synthesis of organic compounds.
Significance
Photochemistry bridges physics and chemistry by explaining how light interacts with matter at the molecular level.
It plays a crucial role in understanding natural processes like photosynthesis and vision, as well as modern technological applications in photovoltaics, photodynamic therapy, and light-driven chemical synthesis.
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