Chemical Bonds: An Introduction to Atomic and Molecular Structure

This book is intended to provide a reasonably complete introduction to atomic and molecular structure and bonding for science students. Parts of the book are revised and expanded versions of appropriate sections from Basic Principles of Chemistry, which I coauthored with Gilbert P. Haight, Jr. The basic approach of using illustrations profusely in presenting concepts has been retained in this monograph. The material on molecular structure is organized roughly in order of molecular size, proceeding from diatomic molecules in Chapter 3 to the "infinitely large" atomic clusters in Chapter 6, which deals with the structures of solids. Although Chapter 3 is loaded with "teaching molecules" (simple molecules observed only at high temperatures and low pressures), the emphasis in the rest of the book is on "real molecules." Each chapter concludes with a large selection of questions and problems

Uncertainty Estimates for Theoretical Atomic and Molecular Data

Sources of uncertainty are reviewed for calculated atomic and molecular data that are important for plasma modeling: atomic and molecular structure and cross sections for electron-atom, electron-molecule, and heavy particle collisions. We concentrate on model uncertainties due to approximations to the fundamental many-body quantum mechanical equations and we aim to provide guidelines to estimate uncertainties as a routine part of computations of data for structure and scattering.Comment: 65 pages, 18 Figures, 3 Tables. J. Phys. D: Appl. Phys. Final accepted versio

Ultracold collision properties of metastable alkaline-earth atoms

Ultra-cold collisions of spin-polarized 24Mg,40Ca, and 88Sr in the metastable 3P2 excited state are investigated. We calculate the long-range interaction potentials and estimate the scattering length and the collisional loss rate as a function of magnetic field. The estimates are based on molecular potentials between 3P2 alkaline-earth atoms obtained from ab initio atomic and molecular structure calculations. The scattering lengths show resonance behavior due to the appearance of a molecular bound state in a purely long-range interaction potential and are positive for magnetic fields below 50 mT. A loss-rate model shows that losses should be smallest near zero magnetic field and for fields slightly larger than the resonance field, where the scattering length is also positive.Comment: 4 pages, 4 figure

Picture this: the value of multiple visual representations for student learning of quantum concepts in general chemistry

Mental models for scientific learning are often defined as, "cognitive tools situated between experiments and theories" (Duschl & Grandy, 2012). In learning, these cognitive tools are used to not only take in new information, but to help problem solve in new contexts. Nancy Nersessian (2008) describes a mental model as being [loosely] characterized as a representation of a system with interactive parts with representations of those interactions. Models can be qualitative, quantitative, and/or simulative (mental, physical, computational)" (p. 63). If conceptual parts used by the students in science education are inaccurate, then the resulting model will not be useful. Students in college general chemistry courses are presented with multiple abstract topics and often struggle to fit these parts into complete models. This is especially true for topics that are founded on quantum concepts, such as atomic structure and molecular bonding taught in college general chemistry. The objectives of this study were focused on how students use visual tools introduced during instruction to reason with atomic and molecular structure, what misconceptions may be associated with these visual tools, and how visual modeling skills may be taught to support students' use of visual tools for reasoning. The research questions for this study follow from Gilbert's (2008) theory that experts use multiple representations when reasoning and modeling a system, and Kozma and Russell's (2005) theory of representational competence levels. This study finds that as students developed greater command of their understanding of abstract quantum concepts, they spontaneously provided additional representations to describe their more sophisticated models of atomic and molecular structure during interviews. This suggests that when visual modeling with multiple representations is taught, along with the limitations of the representations, it can assist students in the development of models for reasoning about abstract topics such as atomic and molecular structure. There is further gain if students’ difficulties with these representations are targeted through the use additional instruction such as a workbook that requires the students to exercise their visual modeling skills

Review: Electronical Structure and Chemical Bondage

This book is written that teachers desiring a more complete background in the elementary principles of atomic and molecular structure will find this very beneficial

Density Functional Theory calculations and Vibrational assignment of Trimethylhydroquinone (TMHQ)

The spectroscopic techniques are very effective and sensitive tool for study of atomic and molecular structure and also used for qualitative and quantitative analysis of compounds. The Fourier transform infrared and Fourier transform Raman spectra of Trimethyl hydroquinone have been recorded in the region 4000-400 cm-1 and 3500-50 cm-1 respectively.  The equilibrium geometry harmonic vibrational frequencies, infrared intensities  and Raman scattering activities were calculated with Density Functional B3LYP method with 6-31+G(d,p) and 6-311++G(d,p) basis set combination.  A detailed interpretation of the infrared and Raman spectra of Trimethylhydroquinone is reported. Our calculated vibrational frequencies are in good agreement with experimental wavenumbers

Technology Transfer: A View from the Trenches

Dr. Drucker, who has lab-wide responsibility for technology transfer at Argonne National Laboratory, argues that transferring rights in discoveries made through tax supported research to private entities can contribute to public welfare in many ways

Silicon Waveguides and Ring Resonators at 5.5 {\mu}m

We demonstrate low loss ridge waveguides and the first ring resonators for the mid-infrared, for wavelengths ranging from 5.4 to 5.6 {\mu}m. Structures were fabricated using electron-beam lithography on the silicon-on-sapphire material system. Waveguide losses of 4.0 +/- 0.7 dB/cm are achieved, as well as Q-values of 3.0 k.Comment: 4 pages, 4 figures, includes supplemental material

Holographic Methods as Local Probes of the Atomic Order in Solids

In the last fifteen years several techniques based on the holographic principle have been developed for the study of the 3D local order in solids. These methods use various particles: electrons, hard x-ray photons, gamma photons, or neutrons to image the atoms. Although the practical realisation of the various imaging experiments is very different, there is a common thread; the use of inside reference points for holographic imaging. In this paper we outline the basics of atomic resolution holography using inside reference points, especially concentrating to the hard x-ray case. Further, we outline the experimental requirements and what has been practically realized in the last decade. At last we give examples of applications and future perspectives.Comment: 14 pages, 6 figure