Trace measurement of BrO at the ppt level by a transportable mode-locked frequency-doubled cavity-enhanced spectrometer
Abstract
Pptv levels of BrO radical have been detected around 338.5-nm wavelength probing a rotationally structured A←X (7,0) electronic transition using mode-locked cavity-enhanced spectroscopy (ML-CEAS). The spectrometer is composed by a widely tunable, broadband frequency-doubled Ti:Sa mode-locked frequency comb laser injected into a high-finesse optical cavity and a high-resolution spectrometer based on a high-order diffraction grating and a high-sensitivity back-thinned CCD camera. A typical minimum detectable absorption coefficient of 1×10-9 cm-1 in 30 s of acquisition has been achieved, leading to a detection limit of 1.7 parts per trillion of BrO at atmospheric pressure. The compact and robust ultrasensitive broadband UV spectrometer is intended to be employed for in situ long-term direct measurements of BrO and other halogenated radicals, thus responding to the lack of analytical techniques to monitor the concentrations of such highly chemically reactive species.
- Publication:
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Applied Physics B: Lasers and Optics
- Pub Date:
- April 2012
- DOI:
- 10.1007/s00340-011-4812-9
- Bibcode:
- 2012ApPhB.107..205G