We present a combined experimental and theoretical investigation of formaldehyde (H2CO) dissociation to H2 CO at energies just above the threshold for competing H elimination. High-resolution state-resolved imaging measurements velocity distributions reveal two pathways. The first proceeds through well-established transition state produce rotationally excited vibrationally cold H2. second pathway yields in conjunction with highly Quasi-classical trajectory calculations performed on global...

In a recent letter (J. Phys. Chem. A, 2001, 105,1), we argued that, although all major thermochemical tables recommend value of (OH) based on spectroscopic approach, the correct is 0.5 kcal/mol lower as determined from an ion cycle. this paper, expand upon and augment both experimental theoretical arguments presented in letter. particular, three separate experiments (mass-selected photoionization measurements, pulsed-field-ionization photoelectron spectroscopy photoelectron-photoion...

The fidelity of combustion simulations is strongly dependent on the accuracy underlying thermochemical properties for core species that arise as intermediates and products in chemical conversion most fuels. High level theoretical evaluations are coupled with a wide-ranging implementation Active Thermochemical Tables (ATcT) approach to obtain well-validated high predictions 0 K heat formation large set species. In particular, ab initio electronic structure based obtained 348 C, N, O, H...

Concepts, such as hybridization and electronegativity, developed by Linus Pauling (1), Robert Mulliken (2), John Slater (3), others in the 1930s have been powerful rationalizing predicting molecular structure, bond energies, some aspects of reactivity. The power these concepts is exemplified classic exposition, Nature Chemical Bond, (4). In recent years experimental theoretical studies numerous radicals provided an assembly quantitative information concerning excitation relative ordering...

The ab initio calculation of electronic energies for numerous configurations HCO and HOC, a novel method fitting the to global surface are reported. This is used calculate all bound vibrational states nonrotating DCO using Watson Hamiltonian. Some quasibound also reported HOC below saddle point energy. Comparisons made with recent experimental results.

An ab initio transition state theory based procedure for accurately predicting the combination kinetics of two alkyl radicals is described. This employs direct evaluations orientation dependent interaction energies at CASPT2/cc-pvdz level within variable reaction coordinate (VRC-TST). One-dimensional corrections to these are obtained from CAS+1+2/aug-cc-pvtz calculations CH3 + along its path. Direct demonstrate that, least purpose kinetics, corrected potential energy surface an accurate...

The CH3 + OH bimolecular reaction and the dissociation of methanol are studied theoretically at conditions relevant to combustion chemistry. Kinetics for barrierless association H CH2OH CH3O product channels determined in high-pressure limit using variable coordinate transition state theory multireference electronic structure calculations evaluate fragment interaction energies. --> 3CH2 H2O abstraction H2 HCOH H2CO feature localized dynamical bottlenecks treated variational QCISD(T) energies...

Vibrational energies for nonrotating H2CO and D2CO are calculated using unadjusted adjusted ab initio quartic force fields in normal mass-weighted coordinates. Converged obtained uncoupled anharmonic oscillator vibrational self-consistent field basis sets compared with experiment. Strong ‘‘Fermi-like’’ resonances found involving the CH symmetric antisymmetric stretches.

Procedures for accurately predicting the kinetics of hydrogen atom associations with hydrocarbon radicals are described and applied to a series reactions. The approach is based on CASPT2/cc-pvdz evaluations orientation-dependent interaction energies within variable reaction coordinate transition state theory. One-dimensional corrections estimated from CAS+1+2/aug-cc-pvtz H + CH3 reaction, dynamical correction factor 0.9 applied. This corrected CASPT2 yields results that 10% those obtained...

We present a detailed theoretical study of vibrational–rotational excitation and reaction in collisions CO2 with 1.9–2.6 eV hydrogen atoms. Minima saddle points on the potential surface have been characterized using ab initio configuration interaction calculations, global has developed by combination many-body expansion surface-fitting methods. The collision dynamics studied quasiclassical trajectories, vibrational states Fourier-transform action calculation. For non-reactive scattering...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMechanisms of gas-phase and liquid-phase ozonolysisLawrence B. Harding William A. Goddard IIICite this: J. Am. Chem. Soc. 1978, 100, 23, 7180–7188Publication Date (Print):November 1, 1978Publication History Published online1 May 2002Published inissue 1 November 1978https://doi.org/10.1021/ja00491a010RIGHTS & PERMISSIONSArticle Views455Altmetric-Citations143LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum full text article...

Case studies of ten reactions using a variety standard electronic structure methods are presented. These case used to illustrate the usefulness and shortcomings these for various classes reactions. Limited comparisons with experiment made. The studied include four radical–radical combinations, H + CH3 → CH4, C2H6, HCO H2CO CH3CHO, three abstraction reactions, HO2 H2 O2, CO CH4 CO, radical–molecule addition, HCCH C2H3, two molecular decompositions, CH3CHO CO. DFT, MP2, CCSD(T), QCISD(T),...

The ability to predict the pressure dependence of chemical reaction rates would be a great boon kinetic modeling processes such as combustion and atmospheric chemistry. This is intimately related rate collision-induced transitions in energy E angular momentum J. We present scheme for predicting this based on coupling trajectory-based determinations moments E,J-resolved collisional transfer with two-dimensional master equation. completely priori procedure provides means proceeding beyond...

The thermal decomposition of ethanol and its reactions with OH D have been studied both shock tube experiments ab initio transition state theory-based master equation calculations. Dissociation rate constants for measured at high T in reflected waves using optical absorption high-sensitivity H-atom ARAS detection. three dissociation processes that are dominant C2H5OH--> C2H4+H2O (A) -->CH3+CH2OH (B) -->C2H5+OH (C).The coefficient reaction C was directly sensitivity 308 nm a multipass White...

A novel theoretical framework for predicting the branching between roaming and bond fission channels in molecular dissociations is described applied to decomposition of acetaldehyde. This reduced dimensional trajectory (RDT) approach, which motivated by long-range nature roaming, fission, abstraction dynamical bottlenecks, involves propagation rigid-body trajectories on an analytic potential energy surface. The obtained from fits large-scale multireference ab initio electronic structure...

State-of-the-art calculations of the C2H3O2 potential energy surface are presented. A new method is described for computing interaction R + O2 reactions. The method, which combines accurate determination quartet along doublet minimum path with multireference doublet/quartet splitting, decreases uncertainty in and thence rate constants by more than a factor 2. temperature- pressure-dependent coefficients computed using variable reaction coordinate transition-state theory, variational...

A global, single-valued ground-state H2O potential surface for the reaction O(1D)+H2→OH+H has been constructed from a new set of accurate ab initio data using general multidimensional interpolation method. The calculations are multireference, configuration interaction variety and were carried out augmented polarized triple zeta basis sets. method is formulated within framework reproducing kernel Hilbert space theory. expressed as many-body sum single one-body term, three two-body terms,...

There are two experimental approaches to determining ΔHf0°(OH), which produce values of this key thermodynamic quantity that differ by >0.5 kcal/mol. The apparent uncertainty the positive ion cycle approach resides in measurement appearance energy OH+ from H2O, while spectroscopic determination dissociation OH(A2Σ+). In note we present an independent confirms accuracy and enhances precision existing value for ΔHf0°(OH). We also electronic structure calculations OH(A2Σ+) potential curve,...

We report a global potential energy surface for formaldehyde. The is combination of six local fits joined smoothly by five switching functions. are to roughly 80000 CCSD(T)/aug-cc-PVTZ and 53000 MR−CI/aug-cc-PVTZ calculations electronic energies. describes the H2CO minimum, cis trans HCOH isomers, molecular channel, H2+CO, radical H+HCO. properties evaluated analyzing stationary points, one-dimensional cuts, contour plots fit.

We present a global potential energy surface for the 1A″ state of NH2 based on application reproducing kernel Hilbert space interpolation method to high quality ab initio (multireference configuration interaction) results. Extensive quasiclassical trajectory calculations are performed this study N(2D)+H2/D2 reaction dynamics. Comparison is made with lower level [first order interaction (FOCI)] Kobayashi, Takayanagi, Yokoyama, Sato, and Tsunashima (KTYST). find saddle point 2.3 (1.9) kcal/mol...

In this article a global potential energy surface for the 1A′′ state of H2O based on application reproducing kernel Hilbert space interpolation method to high quality ab initio results is presented. The resulting used in conjunction with previously determined 1A′ study O(1D)+H2(HD,D2) reaction dynamics, emphasis influence excited measurable properties such as reactive cross sections, rate coefficients, and product distributions. There threshold about 2 kcal/mol surface, even at 5 kcal/mol,...

Abstract A comprehensive kinetic/thermochemical model for the high-temperature radical chain decomposition of acetylene and polyacetylenes is presented. This mechanism tested against new shock tube data: time-of-flight mass spectra in C4H2/H2, mixtures over 1600-2100K laser schlieren experiments C2H2; covering 2700-3500 K. Some earlier measurements on C2H2, are also modeled. The paper includes a very extensive consideration species thermochemistry, full accord with current consensus, having...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTheoretical studies of the reactions hydrogen atom + methylidyne .fwdarw. carbon and methylene using an ab initio global ground-state potential surface for methyleneLawrence B. Harding, Renee Guadagnini, George C. SchatzCite this: J. Phys. Chem. 1993, 97, 21, 5472–5481Publication Date (Print):May 1, 1993Publication History Published online1 May 2002Published inissue 1...