Uptake of methanol on mixed HNO3/H2O clusters: An absolute pickup cross section

0489300 - ÚFCH JH 2019 RIV US eng J - Journal Article
Pysanenko, Andriy - Lengyel, Jozef - Fárník, Michal
Uptake of methanol on mixed HNO3/H2O clusters: An absolute pickup cross section.
Journal of Chemical Physics. Roč. 148, č. 15 (2018), č. článku 154301. ISSN 0021-9606. E-ISSN 1089-7690
R&D Projects: GA ČR(CZ) GA17-04068S
Institutional support: RVO:61388955
Keywords : large water clusters * aerosol nucleation precursors * sulfuric-acid * electron ionization * ice nanoparticles
OECD category: Physical chemistry
Impact factor: 2.997, year: 2018

The uptake of atmospheric oxidized organics on acid clusters is relevant for atmospheric new particle formation. We investigate the pickup of methanol (CH3OH) on mixed nitric acid-water clusters (HNO3)(M)(H2O)(N) by a combination of mass spectrometry and cluster velocity measurements in a molecular beam. The mass spectra of the mixed clusters exhibit (HNO3)(m)(H2O)(n)H+ series with m = 0-3 and n = 0-12. In addition, CH3OH center dot(HNO3)(m)(H2O)(n)H+ series with very similar patterns appear in the spectra after the methanol pickup. The velocity measurements prove that the undoped (HNO3)(m)(H2O)(n)H+ mass peaks in the pickup spectra originate from the neutral (HNO3)(M)(H2O)(N) clusters which have not picked up any CH3OH molecule, i.e., methanol has not evaporated upon the ionization. Thus the fraction of the doped clusters can be determined and the mean pickup cross section can be estimated, yielding (sigma) over bar (s) approximate to 20 angstrom(2). This is compared to the lower estimate of the mean geometrical cross section (sigma) over bar (g) approximate to 60 angstrom(2) obtained from the theoretical cluster geometries. Thus the ´size´ of the cluster corresponding to the methanol pickup is at least 3-times smaller than its geometrical size. We have introduced a method which can yield the absolute pickup cross sections relevant to the generation and growth of atmospheric aerosols, as illustrated in the example of methanol and nitric acid clusters. Published by AIP Publishing.
Permanent Link: http://hdl.handle.net/11104/0283745