Teledyne T100, Instruction Manual, Page: 222 / 404

Theory Of Operation Teledyne ML - T100 UV Fluorescence SO2 Analyzer
222 06807A(DCNxxxx)
source of the UV light and the affected gas limits the wavelength of the light to
approximately 214 nm. The SO
2
molecules absorbs some of energy from the UV light
causing one of the electrons of each of the affected molecules to move to a higher
energy orbital state.
* 2 SO hv SO
Ia
nm 214 2
    
(Equation 9-1)
The amount SO
2
converted to excited SO
2
* in the sample chamber is dependent on the
average intensity of the UV light ( Ia ) and not its peak intensity because the intensity of
UV light is not constant in every part of the sample chamber. Some of the photons are
absorbed by the SO
2
as the light travels through the sample gas.
Figure 9-1: UV Absorption
The equation for defining the average intensity of the UV light ( Ia ) is:
   
 
2 0
SO ax exp 1 I Ia
  
(Equation 9-2)
Where:
I
0
=
Intensity of the excitation UV light.
a
=
The absorption coefficient of SO
2
(a constant).
SO
2
=
Concentration of SO
2
in the sample chamber.
x
=
The distance between the UV source and the SO
2
molecule(s) being affected
(path length).