Synonyms: 
Methyl vinyl ketone

Proton-Transfer-Reaction Mass Spectrometer

PTR-MS is a state-of-the-art chemical ionization mass spectrometry technique that allows for fast (seconds) and highly sensitive (detection limits in the tens of pptv range) of volatile organic compounds (VOCs). A detailed description of the measurement principle and the instrument can be found at: http://en.wikipedia.org/wiki/Proton-transfer-reaction_mass_spectrometry

The technique was developed in the mid-1990s at the University of Innsbruck in Austria and has since then become a routine and integral part of most tropospheric chemistry field campaigns including INDOEX 1999, SOS 1999, TEXAQS 2000, AOE 2001, BEWA 2002, ECHO 2003, ARCTAS-2008, DISCOVER-AQ 2011 – just to name a few of the campaigns in which the University of Innsbruck measurement team has been involved. An interactive presentation of the airborne PTR-MS instrument can be found at: http://discover-aq.larc.nasa.gov/instruments.php (click on interactive viewer and on PTR-MS)

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Charged-coupled device Actinic Flux Spectroradiometers

The Charged-coupled device Actinic Flux Spectroradiometers (CAFS) instruments measure in situ down- and up-welling radiation and combine to provide 4 pi steradian actinic flux density spectra from 280 to 650 nm. The sampling resolution is ~0.8 nm with a full width at half maximum (FWHM) of 1.7 nm at 297 nm. From the measured flux, photolysis frequencies are calculated for ~40 important atmospheric trace gases including O3, NO2, HCHO, HONO and NO3 using a modified version of the NCAR Tropospheric Ultraviolet and Visible (TUV) radiative transfer model. The absolute spectral sensitivity of the instruments is determined in the laboratory with 1000 W NIST-traceable tungsten-halogen lamps with a wavelength dependent uncertainty of 3–5%. During deployments, spectral sensitivity is assessed with secondary calibration lamps while wavelength assignment is tracked with Hg line sources and comparisons to spectral features in the extraterrestrial flux. The optical collectors are characterized for angular and azimuthal response and the effective planar receptor distance. CAFS have an excellent legacy of performance on the NASA DC-8 and WB-57 platforms during atmospheric chemistry and satellite validation mission. These include AVE Houston 2004 and 2005, PAVE, CR-AVE, TC4, ARCTAS, DC3, SEAC4RS, KORUS-AQ, ATom and FIREX-AQ. For FIREX-AQ, upgraded electronics and cooling reduced noise and allowed for a decrease to 1 Hz acquisition.

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