CO-Laser-Magnetic-Resonance facility for sensitive detection of radical trace gases (NOx, HO2?)
A mid infrared CO-Laser-Magnetic-Resonance spectrometer is introduced which employs polarisation perceptive detection schemes for sensitivity enhancement. Using the magnetic circular birefringence (Faraday effect) or the magnetic circular dichroism a detection limit of Iabs/I <10−7 has been achieved in an extracavity single pass setup with 30cm absorption length and without signal integration. The intracavity application of the polarization sensitive detection method resulted in an improvement of the signal-to-noise ratio by a factor of 30. The detection limit then attains the 10ppt level for NO. As the bending mode vibrational frequency of the hydroperoxyl radical is within the spectral range of the CO laser a detection of HO2 in ambient air may potentially be possible.
KeywordsFaraday Rotation Magnetic Circular Dichroism Longitudinal Magnetic Field Vibration Rotation Isotopic Species
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