Photofragmentation-laser induced fluorescence: a new method for detecting atmospheric trace gases

Area of Science:

• Atmospheric chemistry and physics
• Laser spectroscopy
• Analytical chemistry

Background:

• Direct in situ detection of nonfluorescing molecular species in the atmosphere is challenging.
• Existing methods often suffer from interference from scattering and background fluorescence.
• Sensitive and selective detection of trace gases like NO2, NO3, and HNO2 is crucial for atmospheric monitoring.

Purpose of the Study:

• To introduce a new method, photofragmentation-laser induced fluorescence (PF-LIF), for detecting nonfluorescing molecules.
• To demonstrate the capability of PF-LIF for highly sensitive and selective atmospheric trace gas analysis.
• To propose specific applications for NO2, NO3, and HNO2 detection.

Main Methods:

• Laser photolysis of the target species at wavelength lambda(1) to produce excited photofragments.
• Pumping of photofragments to an excited electronic state using a second laser at wavelength lambda(2).
• Detection of fluorescence at wavelength lambda(3) (lambda(3) < lambda(2) and lambda(1)) for signal generation.

Main Results:

• The PF-LIF technique allows for massive discrimination against Rayleigh and Raman scattering.
• Significant reduction of white noise fluorescence originating from the excitation lasers.
• Calculations indicate high sensitivity for detecting NO2, NO3, and HNO2.

Conclusions:

• Photofragmentation-laser induced fluorescence (PF-LIF) is a promising technique for in situ atmospheric trace gas detection.
• The method offers high sensitivity and selectivity, overcoming limitations of existing techniques.
• PF-LIF is suitable for a range of atmospheric trace gases, including NO2, NO3, and HNO2.