TY - JOUR
T1 - Ionization of N2O4 in contact with water
T2 - Mechanism, time scales and atmospheric implications
AU - Miller, Yifat
AU - Finlayson-Pitts, Barbara J.
AU - Gerber, R. Benny
PY - 2009/9/2
Y1 - 2009/9/2
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=69349097381&partnerID=8YFLogxK
U2 - 10.1021/ja900350g
DO - 10.1021/ja900350g
M3 - ???researchoutput.researchoutputtypes.contributiontojournal.article???
AN - SCOPUS:69349097381
SN - 0002-7863
VL - 131
SP - 12180
EP - 12185
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 34
ER -