Vibrational Excitation and De-Excitation and Charge-Transfer of Molecular Ions in Drift Tubes

Ferguson, E. E.

doi:10.1007/978-3-7091-8773-9_8

Cited by 6 publications

(1 citation statement)

References 27 publications

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“…Concerning (7b) it is, at least, conceivable that this reaction channel also represents a three-body assisted reaction. The first step in reaction (7), namely the formation of an activated collision complex, is independent of the buffer gas and at low temperatures generally occurs at a collision rate (Ferguson, 1984). Assuming an efficiency of 0.3 for reaction (7c) in the NOAA experiment compared to our experiment, the overall rate coefficient for reaction (7) becomes 9.1 x 10 -1° cm 3 s -l which is close to the value of 8 x 10 -~° cm 3 s -1 measured at NOAA.…”

Section: Product Lon Distributionsmentioning

confidence: 99%

Flow reactor and triple quadrupole mass spectrometer investigations of negative ion reactions involving nitric acid: Implications for atmospheric HNO3 detection by chemical ionization mass spectrometry

Möhler

Arnold

1991

J Atmos Chem

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Atmospheric nitric acid measurements by ACIMS (Active Chemical Ionization Mass Spectrometry) are based on ion-molecule reactions of CO3(H20) . and NO~(H20), with HNO 3. We have studied these reactions in the laboratory using a flow tube apparatus with mass spectrometric detection of reactant and product ions. Both product ion distributions and rate coefficients were measured. All reactions were investigated in an N2-buffer (1-3 hPa) at room temperature. The reaction rate coefficients of OH-, O2, 03, CO4, CO3, CO~H~O, NO3, and NO3H20 were measured relative to the known rate k = 3.0 x 10 -9 cm 3 s -1 for the reaction of O-with HNOa. The main product ion of the reaction of CO~HzO with HNO3 was found to be (CO3HNO3)-supporting a previous suggestion made on the basis of balloon-borne ACIMS measurements. For the reaction of bare COS with HNO3 three product ions were observed, namely NO 3, (NO3OH)-, and (CO3HNO3) -. The reaction rate coefficients for CO3H20 (1.7 x 10 -9 cm 3 s -j) and NO3H20 (1.6 x 10 -9 cm 3 s -l) were found to be close to the collision rate. The measured k values for bare CO3 (1.3 x 10 -9 cm 3 s -l) and NO3 (0.7 × 10 -9 cm 3 S -I) are somewhat smaller. The collisional dissociations of CO3(HzO) . , NO~(H/O), (n = 1, 2), (CO3HNO3)-and (NO3HNO3) -, occasionally influencing ACIMS measurements, were also studied. Fragment ion distributions were measured using a triple quadrupole mass spectrometer. The results showed that previous stratospheric nitric acid measurements were unimpaired from collisional dissociation processes whereas these processes played a major role during previous tropospheric measurements leading to an underestimation of nitric acid concentrations. Previous ACIMS HNO 3 detection was also affected by the conversion of CO3(H20), to NO3(H20)n due to ion source-produced neutral radicals. A novel ACIMS ion source was developed in order to avoid these problems and to improve the ACIMS method.

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Section: Product Lon Distributionsmentioning

confidence: 99%