title: Influence of water on anharmonicity, stability, and vibrational energy distribution of hydrogen-bonded adducts in atmospheric reactions: case study of the OH + isoprene reaction intermediate using ab initio molecular dynamics.
abstract: The effect of water on the stability and vibrational states of a hydroxy-isoprene adduct is probed through the introduction of 1-15 water molecules. It is found that when a static nuclear harmonic approximation is invoked there is a substantial red-shift of the alcohol O-H stretch (of the order of 800 cm(-1)) as a result of introduction of water. When potential energy surface sampling and associated anharmonicities are introduced through finite temperature ab initio dynamics, this hydroxy-isoprene OH stretch strongly couples with all the water vibrational modes as well as the hydroxy-isoprene OH bend modes. A new computational technique is introduced to probe the coupling between these modes. The method involves a two-dimensional, time-frequency analysis of the finite temperature vibrational properties. Such an analysis not only provides information about the modes that are coupled as a result of finite-temperature analysis, but also the temporal evolution of such coupling.
authors.affiliation: Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA.
authors.forename: Scott M
authors.initials: SM
authors.lastname: Dietrick
authors.forename: Alexander B
authors.initials: AB
authors.lastname: Pacheco
authors.forename: Prasad
authors.initials: P
authors.lastname: Phatak
authors.forename: Philip S
authors.initials: PS
authors.lastname: Stevens
authors.forename: Srinivasan S
authors.initials: SS
authors.lastname: Iyengar