Sulfur dioxide absorption at DF laser wavelengths.

Area of Science:

• Atmospheric Chemistry
• Spectroscopy
• Laser Physics

Background:

• Accurate measurement of sulfur dioxide (SO2) absorption is vital for atmospheric monitoring and pollution control.
• Understanding SO2 spectral properties at various wavelengths is essential for remote sensing applications.

Purpose of the Study:

• To measure the absorption coefficient of sulfur dioxide (SO2) across twenty deuterium fluoride (DF) laser lines under atmospheric conditions.
• To identify specific wavelengths with significant SO2 absorption for potential atmospheric sensing applications.
• To characterize the pressure dependence and broadening effects of a strongly absorbed SO2 line.

Main Methods:

• Utilized twenty DF laser lines to measure SO2 absorption coefficients.
• Investigated weak absorption around 3.7 micrometers.
• Precisely measured the absorption cross-section of the P(4)(6) line at 3.9843 micrometers and its pressure dependence.

Main Results:

• Weak SO2 absorption (alpha* ≤ 0.003 cm(-1) atm(-1)) was observed at several wavelengths near 3.7 micrometers.
• A strong absorption peak for SO2 was identified at the P(4)(6) DF laser line (3.9843 micrometers) with an absorption coefficient of (0.44 ± 0.01) cm(-1) atm(-1).
• Self-broadening and foreign-gas broadening coefficients for the P(4)(6) line were determined to be between 1.5 and 5 MHz/Torr.

Conclusions:

• The P(4)(6) DF laser line at 3.9843 micrometers is highly suitable for detecting sulfur dioxide (SO2) in the atmosphere due to its strong absorption.
• The spectral characteristics, including pressure broadening, of this line provide valuable data for atmospheric remote sensing and quantitative analysis of SO2 concentrations.