Kinetics of the Reactions of Ozone with Halogen Atoms in the Stratosphere

Abstract

It is well established that reaction cycles involving inorganic halogens contribute to the depletion of ozone in the atmosphere. Here, the kinetics of O3 with halogen atoms (Cl, Br, and I) were investigated between 180 and 400 K, expanding the temperature range relative to prior studies. Canonical variational transition state theory including small curvature tunneling correction (CVT/SCT) were considered, following the construction of the potential energy surfaces. MRCI + Q/aug-ano-pVTZ//MP2/aug-cc-pV(T + d)Z and MRCI + Q/aug-ano-RCC-VTZP//MP2/aug-cc-pV(T + d)Z levels of theory were used to calculate the kinetic parameters. Calculated rate coefficients were used to fit the Arrhenius equations, which are obtained to be k1 = (3.48 ± 0.4) × 10−11 exp[(−301 ± 64)/T] cm3 molecule−1 s−1, k2 = (3.54 ± 0.2) × 10−11 exp[(−990 ± 35)/T] cm3 molecule−1 s−1 and k3 = (1.47 ± 0.1) × 10−11 exp[(−720 ± 42)/T] cm3 molecule−1 s−1 for the reactions of O3 with Cl, Br, and I atoms, respectively. The obtained rate coefficients for the reactions of O3 with halogen atoms using CVT/SCT are compared to the latest recommended rate coefficients by the NASA/JPL and IUPAC evaluations. The reactivity trends and pathways of these reactions are discussed.

Kinetics of the Reactions of Chlorinated Very Short-Lived Substances (VSLSs) with Chlorine Atoms

“…The vibrational frequency scaling factor 0.963 was used for the M062X/aug-cc-pV­(T+d)­Z level of theory . Single-point energy calculations were performed at CCSD­(T) and QCISD­(T) with the aug-cc-pV­(T+d)­Z basis set. , Multireference configuration interaction (MRCI) method calculations including spin–orbit coupling effects (+Q) were carried out using the ORCA program. MRCI+Q in combination with aug-ano-pVTZ and ZORA (zeroth-order regular approximation) was used for refining energies.…”

Theoretical Chemistry of Atmospheric Processes

“…In this Special Issue on "Theoretical Chemistry of Atmospheric Processes", five original research articles report recent findings describing the modelling of reactions and processes taking place in the atmosphere, while a review finishes this Special Issue. The research articles span a variety of subjects: N 2 + H 2 reactive collisions [1], sulfuric acid-base cluster formation [2], the reaction mechanism of ethylbenzene-OH adduct with O 2 and NO 2 [3], kinetics of reactions of ozone with halogen atoms (Cl, Br and I) [4] and an empirical model for ozone concentration highlighting the roles of isoprene and monoterpenes [5]. Finally, a review paper presents us a proposal for a programme of research for theoretical chemistry where atmospheric turbulence is properly discussed [6].…”

“…In the fourth paper, Vijayakumar et al [4] dive into the well known and important subject of stratospheric ozone chemistry and perform a theoretical study on the kinetics of the reactions of ozone with halogen atoms in the stratosphere. Although the importance of halogens as catalysts in the destruction of ozone is well recognized, the number of theoretical studies on the kinetics of O 3 with halogens is relatively low.…”