Experimental Study of Line Parameters of H2S around 1.57

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Experimental Study of Line Parameters of H2S
around 1.57 µm using Telecom Diode Laser
Spectroscopy
A.-W. Liu1, S.-M. Hu1, W.-D. Chen2, 1 Hefei
National Laboratory for Physical Sciences at
Microscale University of Science and Technology
of China Hefei, 230026, China 2 Laboratoire de
Physicochimie de lAtmosphère, CNRS UMR
8101 Université du littoral Côte dOpale 189 A,
Av. Maurice Schumann, 59140 Dunkerque, France
chen_at_univ-littoral.fr
63rd OSU International Symposium on Molecular
Spectroscopy, June 16-20, 2008
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Motivation (1)
Toxic pollutant Hydrogen sulfide (H2S) is a
colorless, toxic, flammable gas. Oil and gas
fields, tankers, production facilities and
industrial petroleum operations have the
potential to emit significant amounts of
H2S. Other sources of H2S include the holds of
ships, mine shafts, paper pulp mills,
swamps, and sewers. H2S also occurs in
natural gas and some well waters. Exposure of
even lower concentrations can result in eye
irritation, sore throat and cough, and shortness
of breath. These symptoms usually disappear in
a few weeks. Long-term, low-level exposure may
result in fatigue, loss of appetite, headaches,
irritability, poor memory, and dizziness.
Higher concentrations of 700-800 ppm can be
fatal.
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Motivation (3)
H2S is one of the two most abundant volcanically
emitted sulfur-bearing species

• Monitoring of changes in the release of
  the principal components of volcanic gases from
  a volcano can be used to provide early
  warning of a volcanic eruption.
• When hydrothermal or meteoric water systems
  are present in the subsurface, an increase in
  SO2 emissions may not be detected at the
  surface. In this case, monitoring of CO2
  and H2S emission rates can be used as
  indicators for magmatic intrusions of the
  environment, because CO2 and H2S emissions are
  less soluble in water.
• In addition, the SO2 / H2S ratio can be used
  for the determination of the drying out of a
  hydrothermal or ground-water system in case of a
  magma intrusion.
• in situ and real time trace gas detection of H2S
  by laser absorption spectroscopy

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Merits of Near-IR Spectroscopy

• Single-mode laser source with output powers of
  up to tens of mW and near room temperature
  operation
• Reliable, compact, long lifetimes and high
  electro-optical conversion efficiency
• Fast tunability of the laser emission
  wavelength and wide spectral coverage
• Availability of fiber optic technology and
  inexpensive auxiliary equipment, such as
  thermoelectric coolers, fiber-coupled
  collimating lenses and optical isolators, low
  noise current drivers and detectors
• Sophisticated approaches for signal
  enhancement (CRDS, ICOS, PAS ...) and noise
  reduction (balanced detection, WMS, FMS ...)

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Air broadening Coefficients Study
(111) 5 3 2 lt- 4 3 2
Equation Y a bx
Adj. R-Square 0.99864
Value Standard Error
a Intercept 3.0509E-4 7.6927E-4
b Slope 1.81724E-4 1.43204E-6
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Summary of Line Parameters of H2S around 1.57µm
(1)
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Application to H2S detection by
Off-AxisIntegrated Cavity Output
Spectroscopy50-cm cell gt 1.8 km optical path
length
Appl. Phys. B90 (2008) 311-315
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Trace Gas Detection of H2S (_at_ 103 Torr) MDC
670 ppb (SNR3) using the 71,6-61,5 and 72,6-62,5
overlapping transitions of the (111) band
(a) OA-ICOS cavity transmission signal (A) and
offset signal (B) when blocking the laser
emission. (b) Cavity transmission signal (curve)
after background correction for laser
intensity ramp and a polynomial baseline
simulation (dash). (c) Absorption spectrum of
2.4 ppm H2S (dots) along with a Voigt fit
(curve).
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Conclusions

• Line intensities, self- and air-broadened
  linewidths of hydrogen sulfide (H2S) have been
  determined in the near-infrared around 1.57
  µm. 25 strong well-isolated lines of the 2n1n2
  and the n1n2n3 bands have been studied at
  292 K for the first time.
• Requirement of line parameters of
• H2S isotopes