Chemistry Reference
In-Depth Information
Coupling
elements
Absorbers
Microwave
waveguide
Lens
0.5 m
Spectrometer
Diaphragm
X
CCD
detector
PC
Microwave quartz
window
Rear window
Plasma region
FIGURE 6.9
Microwave discharge plasma reactor with the optical emission spectroscopy
arrangement for recording spectra. (From Lavrov, B.P. et al.,
Plasma Source. Sci. Technol.
, 12,
576, 2003.)
0.04
0.03
0.02
0.01
0.00
1.5
2.0
2.5
3.0
3.5
Power [kW]
FIGURE 6.10
The concentration ratio of atomic and molecular hydrogen as a function of the
axis of observation below the microwave window:
◦
for 4 cm and
for 2 cm distance. (From
Pipa, A.V., On determination of the degree of dissociation of hydrogen in non-equilibrium
plasma by means of emission spectroscopy, PhD thesis, University of Greifswald, Greifswald,
Germany, 2004.)
in both ground and excited states. The spectral line positions provide species identi-
fication while line profiles are often connected with the gas temperature and relative
intensities provide information about population densities. An important advantage
of AS over OES methods is that only relative intensities need to be measured to
determine absolute concentrations, avoiding the problems of complete instrument
