Increase of the Charge Transfer Rate Coefficients for NO+ and O2+• Reactions with Isoprene Molecules at Elevated Interaction Energies

0500247 - ÚFCH JH 2019 RIV US eng J - Journal Article
Spesyvyi, Anatolii - Sovová, Kristýna - Smith, D. - Španěl, Patrik
Increase of the Charge Transfer Rate Coefficients for NO+ and O2+• Reactions with Isoprene Molecules at Elevated Interaction Energies.
Journal of Physical Chemistry A. Roč. 122, č. 51 (2018), s. 9733-9737. ISSN 1089-5639. E-ISSN 1520-5215
R&D Projects: GA ČR(CZ) GJ17-13157Y
Institutional support: RVO:61388955
Keywords : Atmospheric ionization * Ion flow tube * SIFT-MS
OECD category: Physical chemistry
Impact factor: 2.641, year: 2018

Atmospheric concentrations of isoprene (2-methylbutadiene) in environmental research and in exhaled breath for medical research are usually measured by soft chemical ionization mass spectrometry that relies on a knowledge of the kinetics of the gas phase reactions of H3O+, NO+ or O2+• ions with isoprene molecules. Thus, we have carried out an experimental study of the rate coefficients, k, and product ions distributions for such reactions over a range of ion–molecule interaction energy, Er, (0.05–0.8 eV) in a helium-buffered selected ion flow-drift tube, SIFDT. It is found that contrary to the ion-induced dipole capture model, k for the NO+ and O2+• charge transfer reactions almost doubled over the Er range, while k for the H3O+ proton transfer reaction did not significantly change with Er, as predicted. These results reveal that the reaction mechanism involving ion–molecule capture forming an intermediate complex does not properly describe charge transfer to isoprene molecules. It is important to account for this increase in k with Er in these isoprene charge transfer reactions, and probably for other such reactions, when using drift tube reactors for trace gas analysis.
Permanent Link: http://hdl.handle.net/11104/0292348