Jh. Hu et Jpd. Abbatt, REACTION PROBABILITIES FOR N2O5 HYDROLYSIS ON SULFURIC-ACID AND AMMONIUM-SULFATE AEROSOLS AT ROOM-TEMPERATURE, The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory, 101(5), 1997, pp. 871-878
The uptake coefficients for N2O5 hydrolysis have been measured at room
temperature on micron-sized aerosols composed of both sulfuric acid a
queous solutions and ammonium sulfate solutions. The measurements have
been performed in a laminar flow tube which is coupled to a chemical
ionization mass spectrometer for monitoring the concentration of N2O5
in the gas phase and an optical particle counter which sizes the aeros
ols and determines their number density. The aerosols are generated wi
th an ultrasonic nebulizer from aqueous solutions of either sulfuric a
cid or ammonium sulfate, and their liquid-phase concentration is deter
mined by the relative humidity (RH) set within the flow tube. For both
the sulfuric acid and ammonium sulfate aerosols, the reaction probabi
lity (gamma) is largest for the lowest relative humidities studied: fo
r sulfuric acid aerosols, gamma = 0.05-0.06 for RH = 9-20%, gamma = 0.
02 for RH = 90%; for ammonium sulfate aerosols, gamma = 0.04-0.05 for
RH = 50-69%, gamma = 0.02 for RH = 83-94%. In the case of ammonium sul
fate aerosols, significant reactivity with N2O5 is found at relative h
umidities below the deliquescence point of 80%, consistent with the ob
servation that ammonium sulfate aerosols are readily formed in supersa
turated, liquid states.