Lester Andrews

Bio: Lester Andrews is an academic researcher from University of Virginia. The author has contributed to research in topics: Infrared spectroscopy & Molecule. The author has an hindex of 68, co-authored 888 publications receiving 24613 citations. Previous affiliations of Lester Andrews include Ames Research Center & Environmental Molecular Sciences Laboratory.

Pulsed laser-assisted reactions of boron and nitrogen atoms in a condensing nitrogen stream

Abstract: Pulsed laser evaporation of boron and dissociation of nitrogen have provided B and N atoms for reaction in a condensing nitrogen stream. The major product NNBN and the minor products NBN and BNN were identified by mixed nitrogen and boron isotopic multiplets from the FTIR spectra in solid nitrogen. Nitrogen atoms partiapate in these reactions as verified by the observation of N 3 radical and an intense green glow on annealing.

Infrared Spectra of UO2, UO2+, and UO2- in Solid Neon

Abstract: Reactions of laser-ablated uranium atoms, cations, and electrons with O2 during condensation with excess neon produce UO, UO2, UO3, UO2+, and UO2- as characterized by infrared spectra with oxygen isotopic substitution and B3LYP/pseudopotential calculations. Differences in low-lying states for UO2 give rise to substantial shifts and ground state reversal between argon and neon matrices. A series of B3LYP/pseudopotential calculations has been undertaken on oxide species related to the uranyl dication by the addition of one, two, or three electrons. Several electronic states have been characterized for each species. These simple, low-cost calculations predict vibrational frequencies which match those observed in neon matrices extremely well (typically 3−5% too high). The ground state of neutral UO2 appears to have 3Φu symmetry, while 2Φu ground states are implied for UO2+ and UO2-.

Infrared Spectrum of the Difluoromethyl Radical in Solid Argon

Abstract: The primary products of the reaction of lithium atoms and carbon tetrachloride in solid argon at 15°K are lithium chloride and the trichloromethyl radical, which are identified by infrared spectral studies. Natural chlorine isotopes, carbon 13 and bromine substitution, and loss of CCl3 absorptions with attendant growth of absorptions due to C2Cl6 on sample warming verify the molecular identity. Assignments to the carbon–chlorine stretching vibrations ν1 = 674 and ν3 = 898 cm−1 are supported by normal coordinate calculations, and the weak bending modes ν2 and ν4 were not detected. The stretching force constants Fτ = 3.83 mdyn / A and Fττ = 0.43 mdyn / A are compared with those of other chlorocarbons and BCl3 This comparison supports proposed resonance stabilization of the trichloromethyl radical.

A Chemist's Guide to Density Functional Theory

Abstract: "Chemists familiar with conventional quantum mechanics will applaud and benefit greatly from this particularly instructive, thorough and clearly written exposition of density functional theory: its basis, concepts, terms, implementation, and performance in diverse applications. Users of DFT for structure, energy, and molecular property computations, as well as reaction mechanism studies, are guided to the optimum choices of the most effective methods. Well done!" Paul von RaguE Schleyer "A conspicuous hole in the computational chemist's library is nicely filled by this book, which provides a wide-ranging and pragmatic view of the subject.[...It] should justifiably become the favorite text on the subject for practioneers who aim to use DFT to solve chemical problems." J. F. Stanton, J. Am. Chem. Soc. "The authors' aim is to guide the chemist through basic theoretical and related technical aspects of DFT at an easy-to-understand theoretical level. They succeed admirably." P. C. H. Mitchell, Appl. Organomet. Chem. "The authors have done an excellent service to the chemical community. [...] A Chemist's Guide to Density Functional Theory is exactly what the title suggests. It should be an invaluable source of insight and knowledge for many chemists using DFT approaches to solve chemical problems." M. Kaupp, Angew. Chem.

The density functional formalism, its applications and prospects

Abstract: A scheme that reduces the calculations of ground-state properties of systems of interacting particles exactly to the solution of single-particle Hartree-type equations has obvious advantages. It is not surprising, then, that the density functional formalism, which provides a way of doing this, has received much attention in the past two decades. The quality of the energy surfaces calculated using a simple local-density approximation for exchange and correlation exceeds by far the original expectations. In this work, the authors survey the formalism and some of its applications (in particular to atoms and small molecules) and discuss the reasons for the successes and failures of the local-density approximation and some of its modifications.

The Halogen Bond

Abstract: The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design.

Generation and Detection of Reactive Oxygen Species in Photocatalysis

Abstract: The detection methods and generation mechanisms of the intrinsic reactive oxygen species (ROS), i.e., superoxide anion radical (•O2–), hydrogen peroxide (H2O2), singlet oxygen (1O2), and hydroxyl radical (•OH) in photocatalysis, were surveyed comprehensively. Consequently, the major photocatalyst used in heterogeneous photocatalytic systems was found to be TiO2. However, besides TiO2 some representative photocatalysts were also involved in the discussion. Among the various issues we focused on the detection methods and generation reactions of ROS in the aqueous suspensions of photocatalysts. On the careful account of the experimental results presented so far, we proposed the following apprehension: adsorbed •OH could be regarded as trapped holes, which are involved in a rapid adsorption–desorption equilibrium at the TiO2–solution interface. Because the equilibrium shifts to the adsorption side, trapped holes must be actually the dominant oxidation species whereas •OH in solution would exert the reactivity...

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg