Model T101 Instruction Manual Principles Of Operation
245
Figure 10-1. UV Absorption
The equation for defining the average intensity of the UV light (Ia) is:
20 SOaxexp1IIa
Where: (Equation 10-2)
I0 = Intensity of the excitation UV light.
a = The absorption coefficient of SO2.
SO2 = Concentration of SO2 in the sample chamber.
x = The distance between the UV source and the SO2 molecule(s) being
affected (path length).
The second stage of this reaction occurs after the SO2 reaches its excited state (SO2*).
Because the system will seek the lowest available stable energy state, the SO2* molecule
quickly returns to its ground state (Equation 10-3) by giving off the excess energy in the
form of a photon (h). The wavelength of this fluoresced light is also in the ultraviolet
band but at a longer (lower energy) wavelength centered at 330nm.
nm33022 hvSO*SO
(Equation 10-3)
The amount of detectable UV (F) given off by the decay of the SO2* is affected by the rate
at which this reaction occurs (k).
07266B DCN6485