What is the Difference Between Vibrational Relaxation and Internal Conversion?

Vibrational relaxation and internal conversion are both processes that occur within a molecule after it absorbs energy, often from light. They are related but distinct phenomena:

Vibrational Relaxation: This process involves the redistribution of energy within a molecule from a high vibrational energy level to a lower one. It can occur through intermolecular vibrational energy transfer (IET) or intramolecular vibrational energy transfer (IVR). Vibrational relaxation does not involve a change in the electronic state of the molecule.
Internal Conversion: This process involves the relaxation of an electron from a higher electronic state to a lower one, either through the emission of heat or by transferring energy to the molecule's environment. Internal conversion occurs because of the overlap between vibrational and electronic energy states.

While both processes involve the dissipation of energy within a molecule, vibrational relaxation focuses on the redistribution of energy within the molecule, while internal conversion involves the actual change in the electronic state of the molecule.

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What is the Difference Between Vibrational Relaxation and Internal Conversion?

Comparative Table: Vibrational Relaxation vs Internal Conversion

The main difference between vibrational relaxation and internal conversion lies in the change in energy levels and electronic states. Here is a comparison table highlighting the differences:

Process	Vibrational Relaxation	Internal Conversion
Definition	The change in the occurrence of an electron between two vibrational energy levels.	The change in the occurrence of an electron between two electronic energy levels.
Energy Transfer	Involves the transfer of energy from a vibrational state to another vibrational state or the environment.	Involves the transfer of energy from an electronic state to another electronic state.
Electronic State	Does not involve a change in electronic state.	Involves a change in electronic state.
Energy Direction	Vibrational relaxation can be either endothermic or exothermic.	Internal conversion is an exothermic process.
Jablonski Diagram	Represented as a curved arrow between vibrational levels.	Represented as a curved arrow between two vibrational levels in different electronic states.

In summary, vibrational relaxation is the change in vibrational energy levels without changing the electronic state, while internal conversion involves the relaxation of an electron between two electronic energy levels.

Guilherme Mazui

Guilherme Mazui is graduated in journalism from the Federal University of Minas Gerais (UFMG) and a master's degree in Communication from the University of São Paulo (USP). In addition, he has experience in advertising writing and has worked as a content editor in several companies.