Factors Affecting Quantum yield

[1] Temperature : 

The change of quantum yield with temperature is given by the equation
d(logΦ)/dT = Q/RT²
Where Φ is quantum yield and Q is the amount of heat evolved by the formation of a one-mole substance.
Photochemical decomposition of ammonia increases by about 15% for every 100ํ ℃ temperature increase. It reaches seven-fold by 500 ℃.

[2] Wavelength : 

As frequency increases, the power of light energy increases, so quantum yield increases. In other words, the quantum yield decreases as wavelength increases.

[3] Light Intensity:

As light intensity decreases, quantum yield increases.

[4] Inert gases:

The addition of inert gases increases the quantum yield. This is because inert gases increase the number of starting chains as they may retard the diffusion of the atoms to the walls. This effect will decrease the rate of the chain-terminating steps. Thus, the rate of reaction increases thereby quantum yield increases.