Stability of the Hydrogen Trioxy Radical via Infrared Action Spectroscopy

Abstract

The hydrogen trioxy radical (HO3) has been proposed as an intermediate in several important chemical reactions and relaxation processes involving OH in the atmosphere. In this work, the gas-phase infrared action spectrum of HO3 is obtained in the OH overtone region, along with the product state distribution of the OH fragment following dissociation. The highest observed OH product channel sets an upper limit for the HO-O2 binding energy of 6.12 kcal mol(-1). The experimental stability of HO3 and derived equilibrium constant imply that up to 66% of atmospheric OH may be converted into HO3 in the tropopause region.

An Evaluation of Gas Phase Enthalpies of Formation for Hydrogen-Oxygen (HxOy) Species

“…More recently, Lester and coworkers [161][162][163][164] measured the vibrational predissociation of HO 3 putting an upper limit on its bond dissociation energy D 0 (HO-OO) moving the estimate for the enthalpy of formation upward by about (10 to 15) kJ mol −1 . In 2010, Le Picard et al [160], using a spectroscopic kinetic/equilibrium measurement at low temperatures (87 K to 100 K), determined the bond dissociation energy (D 0 ) relatively precisely (reportedly within about 0.5 kJ mol −1 ) and thus, pinned down the enthalpy http://dx.doi.org/10.6028/jres.121.005 The earlier "high" enthalpies of formation from theory were because of the inability of the single reference methods employed to properly treat HO 3 due to significant spin contamination and the multi-reference character of the wavefunctions (see discussion in references in Table 8).…”

Quantum Dynamics of Oxyhydrogen Complex-Forming Reactions for the HO2 and HO3 Systems

“…The hydrogen trioxy radical (HO 3 ) has been known as an important participant in the combustion [113][114][115][116][117], atmosphere chemistry [118][119][120][121][122][123][124][125], and biological processes [126][127][128][129][130][131]. It is also a very important open shell species in the atmosphere, formed by adduct of OH and O 2 .…”

Theoretical characterization of hydrogen pentoxide, H2O5

“…On the other hand, although these molecules have a small number of atoms, they are strongly correlated; hence sophisticated theoretical methodologies must be used to obtain an adequate description of correlation effects. The most extreme case is the HOOO radical whose enthalpy of formation was not established until 2010 . The infrared spectra of cis and trans HOOO was extremely difficult to observe, and the determination of equilibrium structure is even more challenging .…”

“…The most extreme case is the HOOO radical whose enthalpy of formation was not established until 2010 . The infrared spectra of cis and trans HOOO was extremely difficult to observe, and the determination of equilibrium structure is even more challenging . However, the importance of HOOO in solution and atmospheric chemistry elicited important experimental and theoretical advances that improved our understanding of the chemistry of HOOO.…”