Master Equation Studies of the Unimolecular Decay of Thermalized Methacrolein Oxide: The Impact of Atmospheric Conditions.

Master equation simulations of the unimolecular reaction dynamics of the Criegee intermediate methacrolein oxide (MACR oxide) have been performed under a variety of temperature and pressure conditions. These simulations provide insight into how the unimolecular kinetics vary across temperatures spanning the range 288-320 K. This work has incorporated a new potential energy surface and includes the anti-to-syn and cis-to-trans conformational dynamics of MACR oxide, as well as the unimolecular reactions to form dioxirane and dioxole species.

Reactive quenching of OD A 2Σ+ by H2: translational energy distributions for H- and D-atom product channels.

The H- and D-atom products from collisional quenching of OD A (2)Σ(+) by H(2) are characterized through Doppler spectroscopy using two-photon (2 (2)S ←← 1 (2)S) laser-induced fluorescence. Partial deuteration enables separation of the channel forming H + HOD products, which accounts for 75% of reactive quenching events, from the D + H(2)O product channel. The Doppler profiles, along with those reported previously for other isotopic variants, are transformed into product translational energy distributions using a robust fitting procedure based on discrete velocity basis functions.

Experimental characterization of the weakly anisotropic CN X 2Σ+ + Ne potential from IR-UV double resonance studies of the CN-Ne complex.

IR-UV double resonance spectroscopy has been used to characterize hindered internal rotor states (n(K) = 0(0), 1(1), and 1(0)) of the CN-Ne complex in its ground electronic state with various degrees of CN stretch (ν(CN)) excitation. Rotationally resolved infrared overtone spectra of the CN-Ne complex exhibit perturbations arising from Coriolis coupling between the closely spaced hindered rotor states (1(1) and 1(0)) with two quanta of CN stretch (ν(CN) = 2). A deperturbation analysis is used to obtain accurate rotational constants and associated average CN center-of-mass to Ne separation distances as well as the coupling strength.

Theoretical and experimental studies of collision-induced electronic energy transfer from v=0-3 of the E(0g +) ion-pair state of Br2: collisions with He and Ar.

Collisions of Br(2), prepared in the E(0(g)+) ion-pair (IP) electronic state, with He or Ar result in electronic energy transfer to the D, D', and beta IP states. These events have been examined in experimental and theoretical investigations. Experimentally, analysis of the wavelength resolved emission spectra reveals the distribution of population in the vibrational levels of the final electronic states and the relative efficiencies of He and Ar collisions in promoting a specific electronic energy transfer channel.

Rovibrational resonance effects in collision-induced electronic energy transfer: I2(E,v=0-2)+CF4.

Collisions of I2 in the E(0(g)+) electronic state with CF4 molecules induce electronic energy transfer to the nearby D, beta, and D' ion-pair states. Simulations of dispersed fluorescence spectra reveal collision-induced electronic energy transfer rate constants and final vibrational state distributions within each final electronic state. In comparison with earlier reports on I2(upsilon(E)=0-2) collisions with He or Ar atoms, we find markedly different dynamics when I2, excited to the same rovibronic states, collides with CF4.

Second OH overtone excitation and statistical dissociation dynamics of peroxynitrous acid.

The second OH overtone transition of the trans-perp conformer of peroxynitrous acid (tp-HOONO) is identified using infrared action spectroscopy. HOONO is produced by the recombination of photolytically generated OH and NO(2) radicals, and then cooled in a pulsed supersonic expansion. The second overtone transition is assigned to tp-HOONO based on its vibrational frequency (10 195.

Franck-Condon effects in collision-induced electronic energy transfer: I2(E; v = 1,2) + He, Ar.

Collisions of I2 in the E electronic state with rare gas atoms result in electronic energy transfer to the D, beta, and D' ion-pair electronic states. Rate constants for each of these channels have been measured when I2 is initially prepared in the J = 55, nu = 1 and 2 levels in the E state. The rate constants and effective hard sphere collision cross sections confirm the trends observed when nu = 0 in the E state is initially prepared: He collisions favor population of the D state, while Ar collisions favor population of the beta state.