Figure 10-4: Excitation Lamp Uv Spectrum Before/After Filtration - Teledyne 100E Instruction Manual

Theory Of Operation
that are not needed to produce SO
reacting to light not produced by the SO
UV Source Optical Filter
Zinc-vapor lamps output light at other wavelengths beside the 214nm required for the
SO # SO * transformation including a relatively bright light of the same wavelength at
2 2
which SO * fluoresces as it returns to its SO
2
intensity of the of light emitted by the UV lamp at 330nm is so bright, nearly five orders
of magnitude brighter than that resulting from the SO
SO * fluorescence.
2
BEFORE
5
10
4
10
3
10
2
10
1
10
1
0
100 200

Figure 10-4: Excitation Lamp UV Spectrum Before/After Filtration

To solve this problem, the light emitted by the excitation UV lamp passes through a
bandpass filter that screens out photons with wavelengths outside the spectrum required
to excite SO into SO
2
PMT Optical Filter
The PMT used in the Model 100E reacts to a wide spectrum of light which includes much
of the visible spectrum and most of the UV spectrum. Even though the 214 nm light used
to excite the SO is focused away from the PMT, some of it scatters in the direction of the
2
PMT as it interacts with the sample gas. A second optical bandpass filter placed between
the sample chamber (see Figure 10-2) and the PMT strips away light outside of the
fluorescence spectrum of decaying SO
the source lamp and other stray light.
168
*. The second stage protects the PMT detector from
2
SO *
2
Fluorescent
Spectrum
300 400
WAVELENGTH (nm)
*. (Figure 10-4).
2
Model 100E Instruction Manual
* returning to its ground state.
2
ground state (330 nm). In fact, the
2
* decay, it would drown out the
2
UV SOURCE OPTICAL FILTER
5
10
4
10
3
10
2
10
1
10
1
0
500 100
* (see Figure 10-5) including reflected UV form
2
AFTER
BANDWIDTH
SO
2
200 300 400
WAVELENGTH (nm)
045150102 Rev XB1
* FLUORESCENT
SPECTRUM
500