Sujata Guha

An ab initio study of the pathways for the reaction between CH3O2 and BrO radicals

The pathways for the reaction between methylperoxy (CH3O2) and bromine monoxide (BrO) radicals have been examined by using the quadratic configuration interaction method. It is found that the most feasible pathway of the CH3O2+BrO reaction is the formation of CH3OOOBr as an intermediate during the reaction and its dissociation into CH2O and HOOBr. This study finds that besides CH3OOOBr, CH3OOBrO may also exist as an intermediate complex during the CH3O2+BrO reaction.

The isomerization of HOOBr to HOBrO

Abstract A second transition state for the process of isomerization of HOOBr→HOBrO has been located theoretically, using ab initio molecular orbital methods. The energy barrier for this isomerization pathway is found to be 39.4 kcal mol −1 . This result suggests that the barrier is sufficiently high so as not to facilitate the isomerization of HOOBr to HOBrO.

An ab initio study of the low-lying electronic excited states of CH3OBr

Abstract Using high level ab initio molecular orbital methods, theoretical studies were performed on the low-lying excited states of CH 3 OBr. The complete active space self-consistent field (CASSCF) and multi-reference configuration interaction (MRCI) methods, with the cc-pVTZ basis set, were used to calculate the vertical excitation energies for the lowest three 1 A ′ , two 1 A ″ , two 3 A ′ , and two 3 A ″ states. The CASSCF method was used to obtain the potential energy curves for the lowest three 1 A ′ , two 1 A ″ , two 3 A ′ , and two 3 A ″ states of CH 3 OBr along the O–Br coordinate. All of the eight excited states were found to be strongly repulsive along the O–Br coordinate.

An investigation of the formation of OBrO radicals from the HO + HOBrO reaction

Abstract The geometries, vibrational spectra, and relative energetics of the formation of OBrO radicals during the reaction between hydroxyl radicals and HOBrO have been examined by using various ab initio methods. The heat of reaction for the formation of OBrO radicals from the reaction between HO and HOBrO is −37.0 kcal mol −1 , while the energy barrier for activation of the reaction is 3.9 kcal mol −1 . Results suggest that the reaction between HO and HOBrO species could serve as a minor source of OBrO radicals in the atmosphere.