Ionization of N2O4 in contact with water: Mechanism, time scales and atmospheric implications

Yifat Miller, Barbara J. Finlayson-Pitts, R. Benny Gerber

Research output: Contribution to journalArticlepeer-review

67 Scopus citations


Ionization of N2O4 in and on thin water films on surfaces is believed to be a key step in the hydrolysis of NO2 which generates HONO, a significant precursor to the OH free radical in the lower atmosphere. Molecular dynamics simulations using "on the fly" high-level MP2 potentials are carried out for ONONO2·(H 2O)n clusters, n ≤ 8, used to mimic the surface reaction, in order to investigate the ionization process and determine its time-scale and mechanism around room temperature. The results are (i) the isolated molecule does not convert to the NO+NO3 - ion pair, even for long times; (ii) for ONONO2· (H2O)n with n = 1 and 2, ionization takes place in several picoseconds; (iii) for n ≥ 3, ionization is essentially immediate, implying that the neutral species does not have sufficient lifetime to be considered a significant intermediate in the reaction; and (iv) even at ice temperatures, T ≤ 250 K, ionization for n ≥ 3 is immediate. The implications for hydrolysis of oxides of nitrogen on surfaces in the atmosphere are discussed.

Original languageEnglish
Pages (from-to)12180-12185
Number of pages6
JournalJournal of the American Chemical Society
Issue number34
StatePublished - 2 Sep 2009
Externally publishedYes

ASJC Scopus subject areas

  • Catalysis
  • Chemistry (all)
  • Biochemistry
  • Colloid and Surface Chemistry


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