Q

Quantum Yield

Φ = events / photons absorbed
Quick Reference
Formula / NotationΦ = events / photons absorbed
Also Known AsPhotochemical quantum yield, fluorescence quantum yield, Φ, photon efficiency

What is Quantum Yield?

Quantum yield (Φ) is the ratio of the number of events (photons emitted, molecules reacted, electrons produced) to the number of photons absorbed. In photochemistry, it measures the efficiency of a photochemical reaction. In fluorescence, it is the fraction of absorbed photons that result in fluorescent emission. A quantum yield of 1 means every absorbed photon produces one event.

Formula & Notation

Φ = events / photons absorbed

Other Names / Synonyms: Photochemical quantum yield, fluorescence quantum yield, Φ, photon efficiency

Properties & Characteristics

Φ = (number of events) / (number of photons absorbed). Range: 0 to 1 for emission processes. Can exceed 1 for chain reactions (e.g., HCl synthesis: Φ up to 10⁶). Fluorescence quantum yield: Φ_f = k_f / (k_f + k_nr). Affected by: competing deactivation pathways, quenching, solvent. High Φ: efficient fluorophore or photoreaction.

Uses & Applications

Fluorescent dye selection for microscopy and sensing. Photovoltaic cell efficiency. Photosynthesis efficiency measurement. Photocatalysis optimization. Photographic film sensitivity. LED efficiency. Phototherapy dosimetry. Atmospheric photochemical modeling.

Safety Information

Photochemical reactions may involve UV/visible radiation hazards. High quantum yield photoreactions can proceed rapidly. Some photochemical products may be toxic.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Quantum Yield
Formula Φ = events / photons absorbed
Synonyms Photochemical quantum yield, fluorescence quantum yield, Φ, photon efficiency

Frequently Asked Questions

Quantum yield (Φ) is the ratio of the number of events (photons emitted, molecules reacted, electrons produced) to the number of photons absorbed. In photochemistry, it measures the efficiency of a photochemical reaction. In fluorescence, it is the fraction of absorbed photons that result in fluorescent emission. A quantum yield of 1 means every absorbed photon produces one event.

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