The present article provides an account of recent progress in the use of quantum mechanical tools for understanding structure and processes for systems of relevance in atmospheric chemistry. The focus is on problems triggered by experimental activity in this laboratory on investigations of intermolecular interactions by molecular beam scattering. Regarding the major components of the atmosphere, results are summarized on dimers (N2-N2, O2-O2, N2-O2) where experimental and phenomenogically derived potential energy surfaces have been used to compute quantum mechanically the intermolecular clusters dynamics. Rovibrational levels and wave functions are obtained, for perspective use in atmospheric modelling, specifically of radiative absorption of weakly bound complexes. Further work has involved interactions of paramount importance, those of water, for which state-of-the-art quantum chemical calculations for its complexes with rare gases yield complementary information on the interaction (specifically the anisotropies) with respect to molecular beam scattering experiments that measure essentially the isotropic forces. Similar approaches and results have been pursued and obtained for H2S. Stimulated in part by the interesting problem of large amplitude vibrations, such as the chirality change transitions associated with the torsional motions around OO and SS bonds, a systematic series of quantum chemical studies has been undertaken on systems that play also roles in the photochemistry of the minor components of the atmosphere. They are H2O2, H2S2 and several molecules obtained by substitutions of the hydrogens by alkyl groups or halogens. Quantum chemistry is shown to have reached the stage of resolving many previously controversial features regarding these series of molecules (dipole moment, equilibrium geometries, heights of barriers for torsion), which are crucial for intramolecular dynamics. Quantum dynamics calculations are also performed to compute torsional levels and the temperature dependence of their distributions.
Elementary Processes in Atmospheric Chemistry: Quantum Studies of Intermolecular Dimer Formation and Intramolecular Dynamics
MACIEL, GLAUCIETE SARMENTO;CAPPELLETTI, David Michele;GROSSI, Gaia;PIRANI, Fernando;AQUILANTI, Vincenzo
2008
Abstract
The present article provides an account of recent progress in the use of quantum mechanical tools for understanding structure and processes for systems of relevance in atmospheric chemistry. The focus is on problems triggered by experimental activity in this laboratory on investigations of intermolecular interactions by molecular beam scattering. Regarding the major components of the atmosphere, results are summarized on dimers (N2-N2, O2-O2, N2-O2) where experimental and phenomenogically derived potential energy surfaces have been used to compute quantum mechanically the intermolecular clusters dynamics. Rovibrational levels and wave functions are obtained, for perspective use in atmospheric modelling, specifically of radiative absorption of weakly bound complexes. Further work has involved interactions of paramount importance, those of water, for which state-of-the-art quantum chemical calculations for its complexes with rare gases yield complementary information on the interaction (specifically the anisotropies) with respect to molecular beam scattering experiments that measure essentially the isotropic forces. Similar approaches and results have been pursued and obtained for H2S. Stimulated in part by the interesting problem of large amplitude vibrations, such as the chirality change transitions associated with the torsional motions around OO and SS bonds, a systematic series of quantum chemical studies has been undertaken on systems that play also roles in the photochemistry of the minor components of the atmosphere. They are H2O2, H2S2 and several molecules obtained by substitutions of the hydrogens by alkyl groups or halogens. Quantum chemistry is shown to have reached the stage of resolving many previously controversial features regarding these series of molecules (dipole moment, equilibrium geometries, heights of barriers for torsion), which are crucial for intramolecular dynamics. Quantum dynamics calculations are also performed to compute torsional levels and the temperature dependence of their distributions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
