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Kent M. Ervin

Bio: Kent M. Ervin is an academic researcher from University of Nevada, Reno. The author has contributed to research in topics: Dissociation (chemistry) & X-ray photoelectron spectroscopy. The author has an hindex of 10, co-authored 16 publications receiving 1605 citations.

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TL;DR: In this paper, negative ion photoelectron spectra of Cu−n, Ag−n(n=1-10), and Au−n (n= 1-5) are presented for electron binding energies up to 3.35 eV at an instrumental resolution of 6-9 meV.
Abstract: Negative ion photoelectron spectra of Cu−n, Ag−n(n=1–10), and Au−n (n=1–5) are presented for electron binding energies up to 3.35 eV at an instrumental resolution of 6–9 meV. The metal cluster anions are prepared in a flowing afterglow ion source with a cold cathode dc discharge. In the spectra of Cu−2, Ag−2, and Au−2, the M2 X 1Σ+g←M−2 X 2Σ+u transitions are vibrationally resolved. We analyze these spectra to yield the adiabatic electron affinities, vibrational frequencies, bond length changes, and dissociation energies. The a 3Σ+u triplet states of Cu2 and Ag2 are also observed. Using experimental and theoretical data, we assign the major features in the Cu−3 and Ag−3 spectra to the transition from the linear ground state of the anion (M−31Σ+g) to an excited linear state of the neutral (M3 2Σ+u). The Au−3 spectrum is attributed to a two‐photon process, photodissociation followed by photodetachment of the Au− or Au−2 fragment. For larger clusters, we measure the threshold and vertical detachment energies...

518 citations

Journal ArticleDOI
TL;DR: Negative ion photoelectron spectroscopy and gas-phase proton transfer kinetics were employed to determine the CH bond dissociation energies of acetylene, ethylene, and vinyl radical.
Abstract: Negative ion photoelectron spectroscopy and gas-phase proton transfer kinetics were employed to determine the CH bond dissociation energies of acetylene, ethylene, and vinyl radical: Do(HCC-H) = 131.3 f 0.7 kcal mol-', Do(CH2CH-H) = 109.7 f 0.8 kcal mol-', and Do(CH2C-H) = 81.0 f 3.5 kcal mol-'. The strengths of each of the other CH and CC bonds in acetylene and ethylene and their fragments were derived. The energy required to isomerize acetylene to vinylidene was also determined: HCWH - H2C=C: AHbo = 47.4 f 4.0 kcal mol-'. As part of this study, proton transfer kinetics in a flowing afterglow/selected-ion flow tube apparatus were used to refine the acidities of ethylene, acetylene, and vinyl. The gas-phase acidity of acetylene was tied to the precisely known values for hydrogen fluoride, AGsdd298(HF) = 365.6 f 0.2 kcal mol-', and water, AG-(H20) = 383.9 f 0.3 kcal mor', yielding AG-(HCC-H) = 369.8 f 0.6 kcal mol-'. The gas-phase acidity equilibria of acetylene with isopropyl alcohol and terr-butyl alcohol were also measured. Combined with relative acidities from the literature, these measurements yielded improved acidities for the alcohols, AGad,298( (CH3)2CHO-H) = 370.1 f 0.6 kcal mol-', AGaa298((CH3)3CO-H) = 369.3 f 0.6 kcal mol-', hGadd,298(C2HSO-H) = 372.0 f 0.6 kcal mol-', and AGacid.298(CH30-H) = 375.1 f 0.6 kcal mol-'. The gas-phase acidity of ethylene was measured relative to ammonia, AGacid.298(NH3) = 396.5 f 0.4 kcal mol-', giving AGadJ98(C2H1) = 401.0 f 0.5 kcal mol-'. The gas-phase acidity of vinyl radical was bracketed, 375.1 f 0.6 kcal mol-' I AGaaB8(CH2C-H) I 380.4 f 0.3 kcal mol-'. The electron affinities of ethynyl, vinyl, and vinylidene radicals were determined by photoelectron spectroscopy: EA(HCC) = 2.969 f 0.010 eV, EA(CH2CH) = 0.667 f 0.024 eV, and EA(CH2C) = 0.490 f 0.006 eV.

373 citations

Journal ArticleDOI
TL;DR: Theoretical calculations and experimental values from the recent literature are used to construct and evaluate a high precision gas-phase acidity scale as mentioned in this paper, which is applied to previous thermokinetic or equilibrium measurements of the acidities of small alkanols, ethene and benzene.
Abstract: Theoretical calculations and experimental values from the recent literature are used to construct and evaluate a high precision gas-phase acidity scale. Gas-phase acidities at 0 K are evaluated for 12 reference species with accurately known acidities. Using recent spectroscopic results, small but significant revisions are presented for the acidities of ammonia, water, and formaldehyde. These revised anchor acidities are applied to previous thermokinetic or equilibrium measurements of the acidities of small alkanols, ethene, and benzene. Combined with electron affinities from literature negative ion photoelectron spectroscopy measurements, the revised acidities yield the following improved bond dissociation enthalpies: D298(CH3O−H) = 437.7 ± 2.8 kJ/mol, D298(C2H5O−H) = 438.1 ± 3.3 kJ/mol, D298((CH3)2CHO−H) = 442.3 ± 2.8 kJ/mol, D298((CH3)3CO−H) = 444.9 ± 2.8 kJ/mol, D298(C2H3−H) = 463.0 ± 2.7 kJ/mol, and D298(C6H5BH) = 472.2 ± 2.2 kJ/mol. Calculation of gas-phase acidities at 0 K are investigated for seve...

187 citations

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TL;DR: In this article, the interaction of small transition-metal cluster anions with carbonyl ligands is compared with neutral and cationic clusters under thermal conditions, and the reaction rates of transition metal clusters with carbon monoxide are measured as a function of cluster size.
Abstract: Experimental studies of the interactions of small transition-metal cluster anions with carbonyl ligands are reviewed and compared with neutral and cationic clusters. Under thermal conditions, the reaction rates of transition-metal clusters with carbon monoxide are measured as a function of cluster size. Saturation limits for carbon monoxide addition can be related to the geometric structures of the clusters. Both energy-resolved threshold collision-induced dissociation experiments and time-resolved photodissociation experiments are used to measure metal-carbonyl binding energies. For platinum and palladium trimer anions, the carbonyl binding energies are assigned to different geometric binding sites. Platinum and palladium cluster anions catalyse the oxidation of carbon monoxide to carbon dioxide in a full catalytic cycle at thermal energies.

104 citations


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TL;DR: The Gaussian-2 theoretical procedure (G2 theory) as discussed by the authors was proposed to calculate molecular energies (atomization energies, ionization potentials, and electron affinities) of compounds containing first and second-row atoms.
Abstract: The Gaussian‐2 theoretical procedure (G2 theory), based on a b i n i t i o molecular orbital theory, for calculation of molecular energies (atomization energies, ionization potentials,electron affinities, and proton affinities) of compounds containing first‐ (Li–F) and second‐row atoms (Na–Cl) is presented. This new theoretical procedure adds three features to G1 theory [J. Chem. Phys. 9 0, 5622 (1989)] including a correction for nonadditivity of diffuse‐s p and 2d f basis set extensions, a basis set extension containing a third d function on nonhydrogen and a second p function on hydrogen atoms, and a modification of the higher level correction. G2 theory is a significant improvement over G1 theory because it eliminates a number of deficiencies present in G1 theory. Of particular importance is the improvement in atomization energies of ionic molecules such as LiF and hydrides such as C2H6, NH3, N2H4, H2O2, and CH3SH. The average absolute deviation from experiment of atomization energies of 39 first‐row compounds is reduced from 1.42 to 0.92 kcal/mol. In addition, G2 theory gives improved performance for hypervalent species and electron affinities of second‐row species (the average deviation from experiment of electron affinities of second‐row species is reduced from 1.94 to 1.08 kcal/mol). Finally, G2 atomization energies for another 43 molecules, not previously studied with G1 theory, many of which have uncertain experimental data, are presented and differences with experiment are assessed.

3,216 citations

Journal ArticleDOI
TL;DR: In this paper, a list of reliable bond energies that are based on a set of critically evaluated experiments is provided and a brief description of the three most important experimental techniques for measuring bond energies is provided.
Abstract: In this Account we have compiled a list of reliable bond energies that are based on a set of critically evaluated experiments. A brief description of the three most important experimental techniques for measuring bond energies is provided. We demonstrate how these experimental data can be applied to yield the heats of formation of organic radicals and the bond enthalpies of more than 100 representative organic molecules.

2,415 citations

Journal Article
TL;DR: This Account presents a list of reliable bond energies that are based on a set of critically evaluated experiments and demonstrates how these experimental data can be applied to yield the heats of formation of organic radicals and the bond enthalpies of more than 100 representative organic molecules.
Abstract: In this Account we have compiled a list of reliable bond energies that are based on a set of critically evaluated experiments. A brief description of the three most important experimental techniques for measuring bond energies is provided. We demonstrate how these experimental data can be applied to yield the heats of formation of organic radicals and the bond enthalpies of more than 100 representative organic molecules.

1,869 citations

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TL;DR: In this paper, a review of the experimental methods for the production of free nanoclusters is presented, along with theoretical and simulation issues, always discussed in close connection with the experimental results.
Abstract: The structural properties of free nanoclusters are reviewed. Special attention is paid to the interplay of energetic, thermodynamic, and kinetic factors in the explanation of cluster structures that are actually observed in experiments. The review starts with a brief summary of the experimental methods for the production of free nanoclusters and then considers theoretical and simulation issues, always discussed in close connection with the experimental results. The energetic properties are treated first, along with methods for modeling elementary constituent interactions and for global optimization on the cluster potential-energy surface. After that, a section on cluster thermodynamics follows. The discussion includes the analysis of solid-solid structural transitions and of melting, with its size dependence. The last section is devoted to the growth kinetics of free nanoclusters and treats the growth of isolated clusters and their coalescence. Several specific systems are analyzed.

1,563 citations

Journal ArticleDOI
TL;DR: This issue discusses proton-coupled electron transfer or PCET processes, which are central to a great many chemical and biochemical processes, from biological catalysis and energy transduction, to bulk industrial chemical processes, to new approaches to solar energy conversion.
Abstract: Many, if not most, redox reactions are coupled to proton transfers. This includes most common sources of chemical potential energy, from the bioenergetic processes that power cells to the fossil fuel combustion that powers cars. These proton-coupled electron transfer or PCET processes may involve multiple electrons and multiple protons, as in the 4 e–, 4 H+ reduction of dioxygen (O2) to water (eq 1), or can involve one electron and one proton such as the formation of tyrosyl radicals from tyrosine residues (TyrOH) in enzymatic catalytic cycles (eq 2). In addition, many multi-electron, multi-proton processes proceed in one-electron and one-proton steps. Organic reactions that proceed in one-electron steps involve radical intermediates, which play critical roles in a wide range of chemical, biological, and industrial processes. This broad and diverse class of PCET reactions are central to a great many chemical and biochemical processes, from biological catalysis and energy transduction, to bulk industrial chemical processes, to new approaches to solar energy conversion. PCET is therefore of broad and increasing interest, as illustrated by this issue and a number of other recent reviews.

1,226 citations