تسجيل الدخول

تسجيل

The overall quantum yield of a photochemical reaction

المؤلف:  Peter Atkins، Julio de Paula

المصدر:  ATKINS PHYSICAL CHEMISTRY

الجزء والصفحة:  859

2025-12-28

348

The overall quantum yield of a photochemical reaction

For complex reactions involving secondary processes, such as chain reactions initiated by photolysis, many reactant molecules might be consumed as a result of absorption of a single photon. The overall quantum yield, Φ, for such reactions, the number of reactant molecules consumed per photon absorbed, might exceed 1. In the photolysis of HI, for example, the processes are

HI+ hν →H·+I·

H· +HI→H2+I·

I· + I· + M→I2+M*

The overall quantum yield is 2 because the absorption of one photon leads to the destruction of two HI molecules. In a chain reaction, Φ may be very large, and values of about 10⁴ are common. In such cases the chain acts as a chemical amplifier of the initial absorption step.