Kinetics study of the reaction HO + HNO₃

Abstract

The reaction clude a n estimate of the measurement accuracy. No dependence of k, on pressure a t 300 K is observed in studies between 1-and lO-torr helium. An upper limit of k, < l % k , a t 300 K is given.

Temperature-(208–318 K) and pressure-(18–696 Torr) dependent rate coefficients for the reaction between OH and HNO&lt;sub&gt;3&lt;/sub&gt;

“…Brown et al (1999) quote a 213.86 nm absorption cross section of (4.52 ± 0.19) × 10 −19 cm 2 molecule −1 , obtained by interpolating the HNO 3 absorption spectrum of Burkholder et al (1993) This value agrees well with that obtained in the present experiment. A very similar value of σ 183.95 nm = 1.63 × 10 −17 cm 2 molecule −1 was first determined by Biaume (1973Biaume ( -1974 and confirmed by Wine et al (1981) and Connell and Howard (1985). The excellent agreement with previous results indicates that our absorption cross sections are well suited for the in situ optical determination of HNO 3 concentrations.…”

“…Only at pressures much lower than those achievable with the present set-up does the temperature dependence show a significant change in the apparent (negative) activation energy, e.g. with a value of k 5 = 2 × 10 −14 exp(430/T ) cm 3 molecule −1 s −1 obtained in a few Torr of He (Connell and Howard, 1985).…”

“…The important atmospheric role of the reaction between OH and HNO 3 is reflected in the numerous experimental determinations of the rate coefficient (k 5 ) and the products as listed and reviewed by evaluation panels (Atkinson et al, 2004;Sander et al, 2006). Most of the experimental studies were carried out in the mid-70s to mid-80s (Margitan et al, 1975;Smith and Zellner, 1975;Wine et al, 1981;Jourdain et al, 1982;Kurylo et al, 1982;Margitan and Watson, 1982;Marinelli and Johnston, 1982;Ravishankara et al, 1982;Devolder et al, 1984;Smith et al, 1984;Connell and Howard, 1985;Jolly et al, 1985;Stachnik et al, 1986) with only the most recent and comprehensive studies of the reaction (Brown et al, 1999(Brown et al, , 2001) extending the temperature range to those found at the tropopause. Experimental (Carl et al, 2001;McCabe et al, 2003;O'Donnell et al, 2008b) and theoretical (Xia and Lin, 2001;Gonzalez and Anglada, 2010) work examining the details of the reaction mechanism highlight continuing interest in this complex reaction, which proceeds via formation of a pre-reaction complex, HO-HNO 3 (Aloisio and Francisco, 1999;Brown et al, 1999Brown et al, , 2001Xia and Lin, 2001;O'Donnell et al, 2008a).…”

Reactions of OH radicals with inorganic compounds in the gas phase

“…At room temperature the reported absolute rate constants can be grouped around two values, 5.2 x 101° and 8.0 x 101°, with no adequate explanation for the difference. Temperature dependence studies [133,[136][137][138][139][140][141][142]144], although not in complete agreement at room temperature, give a negative activation energy of about -1.5 kcal/mol. The question of a pressure effect on the rate constant is also not completely resolved, and even two studies from the same laboratory are in conflict.…”

Trace gas exchange at the air/water interface: Measurements of mass accommodation coefficients

“…HNO3 was prepared in pure crystalline form (Connell and Howard, 1985), and evaporated from a cold trap while filling the evacuated glass chamber with synthetic air. The HNO3 concentration in the glass chamber was calculated from the UV absorption spectrum in the 200-225 nm range, using tabulated absorption cross-sections (Molina and Molina, 1981).…”