Measurement of HCI absorption coefficients with a DF laser

Area of Science:

• Spectroscopy
• Atmospheric Science
• Laser Physics

Background:

• Accurate measurement of absorption coefficients is vital for atmospheric monitoring.
• Deuterium fluoride (DF) lasers offer specific wavelengths for probing atmospheric gases.
• Hydrogen chloride (HCl) is a significant atmospheric pollutant and chemical intermediate.

Purpose of the Study:

• To experimentally determine absorption coefficients of HCl at various DF laser transitions.
• To investigate the spectral overlap between DF laser lines and HCl absorption lines.
• To assess the potential of these measurements for applications like differential absorption lidar (DIAL).

Main Methods:

• Experimental measurement of absorption coefficients (k) for HCl in a nitrogen (N2) buffer gas.
• Utilizing several DF laser transitions within the 2439.02 cm(-1) to 2862.87 cm(-1) spectral range.
• Comparing experimental pressure dependence of k with theoretical predictions.

Main Results:

• The 2-1 P(3) DF laser transition was found to overlap the P(6) HCl(37) absorption line within atmospheric broadening.
• Measured absorption coefficient k = 5.64 +/- 0.28 (atm-cm)cm(-1) for a 0.27% HCl/N2 mixture at 760 Torr.
• The 2-1 P(3) DF transition is 1.32 +/- 0.15 GHz from the P(6) HCl line center, agreeing with literature.

Conclusions:

• The spectral alignment of the 2-1 P(3) DF laser and P(6) HCl absorption line is confirmed.
• Multiple DF laser transitions show measurable HCl absorption, supporting their use in remote sensing.
• Results are applicable to differential absorption lidar (DIAL) and heterodyne detection systems.