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- The branching ratio of the O(1D) + HD reaction: a dynamical studyPublication . Rio, Carolina; Brandão, J.The isotopic branching on the reaction of O(1D) + HD has been the subject of several theoretical and experimental studies with results ranging from 1 to 2 for the OD/OH product ratio. We present a study of the dynamics of this reaction using a double-valued potential energy surface for the ground state water molecule. Our results predict a branching ratio close to 2 for this reaction in agreement with statistical studies but in contrast with experiment. This result can be attributed to the formation and dynamics of the intermediate complex.
- A modified potential for HO2 with spectroscopic accuracyPublication . Rio, Carolina; Tennyson, Jonathan; Brandão, J.Seven ground state potential energy surfaces for the hydroperoxyl radical are compared. The potentials were determined from either high-quality ab initio calculations, fits to spectroscopic data, or a combination of the two approaches. Vibration-rotation calculations are performed on each potential and the results compared with experiment. None of the available potentials is entirely satisfactory although the best spectroscopic results are obtained using the Morse oscillator rigid bender internal dynamics potential [Bunker , J. Mol. Spectrosc. 155, 44 (1992)]. We present modifications of the double many-body expansion IV potential of Pastrana [J. Chem. Phys. 94, 8093 (1990)]. These new potentials reproduce the observed vibrational levels and observed vibrational levels and rotational constants, respectively, while preserving the good global properties of the original potential.
- Dynamical studies and product analysis of the reaction between O(1D) and H2/D2Publication . Rio, Carolina; Brandão, J.In this work we study the dynamics of the O (1D) + H2/D2 reactions at fixed collision energies [4,5] using quasiclassical trajectories calculations on a double-valued potential energy surface for H2O [2].
- Dynamical studies and product analysis of O(1D)1H2/D2 reactionsPublication . Rio, Carolina; Brandão, J.The aim of this study was to analyse the dynamics of O(1D)þH2/D2 reactions using quasiclassical trajectory calculations on a double-valued potential energy surface for H2O. Produced on the photodissociation of stratospheric ozone, the excited oxygen atom is a highly reactive species whose chemistry plays a key role in the ozone depletion cycle. In order to make comparisons with experiment, we studied these reactions at fixed translational collision energies. In particular, we consider the reactive cross sections, the thermal rate constants, the opacity function, and the differential cross sections. In addition, we also study the energy distribution of the products and compare the results with experiment and calculations based on phase space statistical theory. Results for the rotational population of the OH products are also compared with experimental results. The agreement between our results and experiment reinforces the accuracy of the H2O potential energy surface used.
- The ground state water molecule and the reactions O(1D) + H2/D2/HD and H + OD that occur in this systemPublication . Rio, Carolina; Brandão, J.; Wang, WenliDue to their importance in atmospheric and combustion chemistry, the reactions of O(1D) with H2 and its isotopic variants HD and D2 have been subject of several theoret- ical1, 2 and experimental2, 3 studies.
- Isotopic effect in the O(1D) + DH reaction and H + OD <- > OH + D equilibrium.Publication . Rio, Carolina; Brandão, J.; Wang, WenliIn this work a recent double-valued potential energy surface for water molecule [1] is used in order to study the isotopic effect in O(1D) + DH reaction, by using quasiclassical trajectory calculations (QCT).
- The dynamics of the reaction between O (1D) and DH and the isotopic effectPublication . Rio, Carolina; Brandão, J.The reaction O(1D) + H2 OH + H and its isotopic variants plays an important role in atmospheric chemistry and also is important in combustion chemistry. It has been taken as a prototype for insertion reactions. As a result, it has been subject of several experimental studies. Also theoretical studies of its dynamics have been carried out.
- Quasiclassical and capture studies on the O (1D) +H2->OH+H reaction using a new potential energy surface for H2OPublication . Rio, Carolina; Brandão, J.In absence of energy barrier, the long-range interactions between reactants should play an important role on the dynamics of the reaction of O(1D) with H2 that mainly occurs in the ground state potential energy surface for H2O. Quasiclassical and capture studies on a new potential energy surface that carefully reproduces these interactions are in close agreement with the most recent estimates for the thermal rate constant, when the effects of the excited surfaces are taken into account.
- Double-valued potential energy surface for H2O derived from accurate ab initio data and including long-range interactionsPublication . Rio, Carolina; Brandão, J.In a recent work we have been able to model the long-range interactions within the H2O molecule. Using these long-range energy terms, a complete potential energy surface has been obtained by fitting high-quality ab initio energies to a double-valued functional form in order to describe the crossing between the two lowest-potential-energy surfaces. The two diabatic surfaces are represented using the double many-body expansion model, and the crossing term is represented using a three-body energy function. To warrant a coherent and accurate description for all the dissociation channels we have refitted the potential energy functions for the H2(3Su 1), OH(2P), and OH(2S) diatomics. To represent the three-body extended Hartree–Fock nonelectrostatic energy terms, V1 , V2 , and V12 , we have chosen a polynomial on the symmetric coordinates times a range factor in a total of 148 coefficients. Although we have not used spectroscopic data in the fitting procedure, vibrational calculations, performed in this new surface using the DVR3D program suite, show a reasonable agreement with experimental data. We have also done a preliminary quasiclassical trajectory study ~300 K!. Our rate constant for the reaction O(1D)1H2(1Sg 1) !OH(2P)1H(2S), k(300 K)5(0.99960.024)310210 cm3 molecule21 s21, is very close to the most recent recommended value. This kinetic result reinforces the importance of the inclusion of the long-range forces when building potential energy surfaces.