Quantum yield

Quantum yield is a measure of the efficiency of photon emission in a photophysical process. It is defined as the ratio of the number of photons emitted to the number of photons absorbed. Quantum yield is a crucial parameter in various fields such as photochemistry, fluorescence spectroscopy, and photosynthesis.

Definition

The quantum yield (Φ) can be mathematically expressed as:

Φ = \(\frac{\text{Number of photons emitted}}{\text{Number of photons absorbed}}\)

Types of Quantum Yield

There are different types of quantum yields depending on the process being measured:

• Fluorescence Quantum Yield: The efficiency of the fluorescence process.
• Phosphorescence Quantum Yield: The efficiency of the phosphorescence process.
• Photochemical Quantum Yield: The efficiency of a photochemical reaction.

Applications

Quantum yield is an important parameter in several applications:

• In fluorescence spectroscopy, it helps in determining the efficiency of fluorescent dyes and proteins.
• In photosynthesis, it is used to measure the efficiency of light conversion in chlorophyll.
• In photovoltaics, it helps in assessing the efficiency of solar cells.

Measurement

Quantum yield can be measured using various techniques:

• Relative method: Comparing the sample with a standard of known quantum yield.
• Absolute method: Using an integrating sphere to measure the total emitted and absorbed photons.

Factors Affecting Quantum Yield

Several factors can influence the quantum yield of a substance:

• Temperature
• Solvent polarity
• Concentration
• Presence of quenchers

Related Pages

• Photochemistry
• Fluorescence spectroscopy
• Photosynthesis
• Chlorophyll
• Photovoltaics
• Quenching (fluorescence)

See Also

• Fluorescence
• Phosphorescence
• Photon
• Absorption (electromagnetic radiation)