Dj. Creasey et al., IMPLEMENTATION AND INITIAL DEPLOYMENT OF A FIELD INSTRUMENT FOR MEASUREMENT OF OH AND HO2 IN THE TROPOSPHERE BY LASER-INDUCED FLUORESCENCE, Journal of the Chemical Society. Faraday transactions, 93(16), 1997, pp. 2907-2913
Citations number
41
Categorie Soggetti
Chemistry Physical","Physics, Atomic, Molecular & Chemical
An instrument to detect atmospheric concentrations of the hydroxyl (OH
) and hydroperoxyl (HO2) radicals has been developed using the FACE (f
luorescence assay by gas expansion) technique. The instrument is house
d in a mobile laboratory and monitors the OH radical via on-resonance
laser-induced fluorescence (LIF) spectroscopy of the A(2) Sigma(+) (up
silon' = 0)-(XIIi)-I-2 (upsilon'' = 0) transition at ca. 308 nm. Ambie
nt air is expanded through a 1 nm nozzle to low pressure where it is i
rradiated by the laser pulse at a repetition rate of 7 kHz, with the r
esultant fluorescence being detected by gated photon counting. HO2 is
monitored by chemical conversion to OH by the addition of NO, with sub
sequent detection using LIF. Following laboratory and held calibration
s to characterise the instrument sensitivity, detection limits of 1.8
x 106 and 2.1 x 10(7) molecule cm-3 were determined for OH and HO2 res
pectively, for a signal-to-noise ratio, S/N, of 1 with 150 s signal in
tegration time. The instrument was deployed for the first time during
the ACSOE field campaign at Mace Head, fire, for which illustrative re
sults are given.