Physical Sciences and Mathematics Commons^™

Initial Investigation Of The Wavelength Dependence Of Optical Properties Measured With A New Multi-Pass Aerosol Extinction Differential Optical Absorption Spectrometer (Ae-Doas), R. T. Chartier, Margaret E. Greenslade

Chemistry

Atmospheric aerosols directly affect climate by scattering and absorbing radiation. The magnitude of the impact is dependent upon the wavelength of light, but is often estimated near 550 nm. When light scattering and absorption by aerosols is approximated, the wavelength dependence of the refractive index for specific components is lost. As a result, climate models would have inherent uncertainties for aerosol contributions to radiative forcing when considering the entire solar spectrum. An aerosol extinction differential optical absorption spectrometer has been developed to directly measure aerosol extinction at mid-ultraviolet to near infrared wavelengths. The instrument consists of a spectrometer coupled to …

Tackling Teaching: Understanding Commonalities Among Chemistry, Mathematics, And Physics Classroom Practices., Samuel Pazicni, Karen A. Marrongelle, Warren Christensen

Chemistry

Abstract:

Education research in chemistry, mathematics, and physics tends to focus on issues inherent to the discipline, most notably content. At this time, little literature evidence exists that documents fruitful collaborations between education specialists across the STEM disciplines. This work seeks to unite the disciplines by investigating a common task: teaching. This study explores how discipline-specific practices influence the common act of reformed teaching pedagogy with a focus on the use of inquiry. We seek to identify commonalities among classroom teaching practices in these disciplines and contribute to the development of analytical tools to study STEM teaching.

A Comparison Of Gc-Fid And Ptr-Ms Toluene Measurements In Ambient Air Under Conditions Of Enhanced Monoterpene Loading, Jesse L. Ambrose, K. Haase, R. S. Russo, Y. Zhou, M. L. White, E. K. Frinak, C. Jordan, Howard R. Mayne, Robert W. Talbot, B. C. Sive

Chemistry

Toluene was measured using both a gas chromatographic system (GC), with a flame ionization detector (FID), and a proton transfer reaction-mass spectrometer (PTR-MS) at the AIRMAP atmospheric monitoring station Thompson Farm (THF) in rural Durham, NH during the summer of 2004. Simultaneous measurements of monoterpenes, including alpha- and beta-pinene, camphene, Delta(3)-carene, and d-limonene, by GC-FID demonstrated large enhancements in monoterpene mixing ratios relative to toluene, with median and maximum enhancement ratios of similar to 2 and similar to 30, respectively. A detailed comparison between the GC-FID and PTR-MS toluene measurements was conducted to test the specificity of PTR-MS for atmospheric …

2,3-Bis(Bromomethyl)-1,4-Diphenylbenzene, Jonathan B. Briggs, Mikael D. Jazdzyk, Glen P. Miller

Chemistry

In the title compound, C(20)H(16)Br(2), the terminal phenyl groups are twisted away from the central ring by approximately 55 and -125 degrees (average of four dihedral angles each), respectively. The crystal structure is stabilized by a combination of interMolecular and intraMolecular interactions including interMolecular pi-pi stacking interactions [C atoms of closest contact = 3.423 ( 5) angstrom].

2,5-Dichlorothiophene 1,1-Dioxide, Jonathan B. Briggs, Wenling Jia, Mikael D. Jazdzyk, Glen P. Miller

Chemistry

The complete molecule of the title compound, C(4)H(2)Cl(2)O(2)S, is generated by crystallographic twofold symmetry, with the S atom lying on the rotation axis. In the crystal, the molecules are linked by C-H center dot center dot center dot O hydrogen bonds..

1,2-Dimethyl-4,5-Diphenylbenzene Determined On A Bruker Smart X2s Benchtop Crystallographic System, Jonathan B. Briggs, Mikael D. Jazdzyk, Glen P. Miller

Chemistry

The title compound, C(20)H(18), has two crystallographically independent molecules in the asymmetric unit. The phenyl substituents of molecule A are twisted away from the plane defined by the central benzene ring by 131.8 (2) and -52.7 (3)degrees. The phenyl substituents of molecule B are twisted by -133.3 (2) and 50.9 (3)degrees. Each molecule is stabilized by a pair of intraMolecular C(aryl, sp(2))-H center dot center dot center dot pi interactions, as well as by several interMolecular C(methyl, sp(3))-H center dot center dot center dot pi interactions.

(2+1) Resonance Enhanced Ionization Spectroscopy Of A State Selected Beam Of Oh Radicals, Margaret E. Greenslade, Marsha I. Lester, Dragana C. Radenovic, Andre J.A. Van Roij, David H. Parker

Chemistry

A state-selected beam of hydroxyl radicals is generated using a pulsed discharge source and hexapole field. The OH radicals are characterized by resonance-enhanced multiphoton ionization (REMPI) spectroscopy via the nested D  and 3  Rydberg states. Simplified spectra are observed from the selected ∣M_J∣ = 3/2 component of the upper Λ-doublet level of the lowest rotational state (J = 3/2) in ground (v″ = 0) and excited(v″ = 1–3) vibrational levels of the OH X  state. Two-photon transitions are observed to the D (v′ = 0–3) and 3 (v′ …

Fluorescence-Dip Infrared Spectroscopy And Predissociation Dynamics Of Oh A (V=4) Radicals, Erika L. Derro, Ilana B. Pollack, Logan P. Dempsey, Margaret E. Greenslade, Yuxiu Lei, Dragana C. Radenovic, Marsha I. Lester

Chemistry

Fluorescence-dip infrared spectroscopy, an UV-IR double-resonance technique, is employed to characterize the line positions, linewidths, and corresponding lifetimes of highly predissociative rovibrational levels of the excited A  electronic state of the OH radical. Various lines of the 4←2 overtone transition in the excited A  state are observed, from which the rotational, centrifugal distortion, and spin-rotation constants for the A  (v = 4) state are determined, along with the vibrational frequency for the overtone transition. Homogeneous linewidths of 0.23–0.31 cm⁻¹ full width at half maximum are extracted from the line profiles, demonstrating that the N = …

Evidence For Partial Quenching Of Orbital Angular Momentum Upon Complex Formation In The Infrared Spectrum Of Oh-Acetylene, Mark D. Marshall, James B. Davey, Margaret E. Greenslade, Marsha I. Lester

Chemistry

The entrance channel leading to the addition reaction between the hydroxyl radical and acetylene has been examined by spectroscopic characterization of the asymmetric CH stretching band of the π-hydrogen bonded OH-acetylene reactant complex. The infrared action spectrum observed at 3278.6 cm⁻¹ (origin) consists of seven peaks of various intensities and widths, and is very different from those previously reported for closed-shell HF/HCl-acetylene complexes. The unusual spectrum arises from a partial quenching of the OH orbital angular momentum in the complex, which in turn is caused by a significant splitting of the OH monomer orbital degeneracy into ²A′ …

Infrared Spectrum And Stability Of A Π-Type Hydrogen-Bonded Complex Between The Oh And C2h2 Reactants, James B. Davey, Margaret E. Greenslade, Mark D. Marshall, Marsha I. Lester, Martyn D. Wheeler

Chemistry

A hydrogen-bonded complex between the hydroxyl radical and acetylene has been stabilized in the reactant channel well leading to the addition reaction and characterized by infrared action spectroscopy in the OH overtone region. Analysis of the rotational band structure associated with the a-type transition observed at 6885.53(1) cm−1 (origin) reveals a T-shaped structure with a 3.327(5) Å separation between the centers of mass of the monomer constituents. The OH (v = 1) product states populated following vibrational predissociation show that dissociation proceeds by two mechanisms: intramolecular vibrational to rotational energy transfer and intermolecular vibrational energy transfer. The highest observed OH …

Photodissociation Of The Od Radical At 226 And 243 Nm, Dragana C. Radenovic, Andre J.A. Van Roij, Dmitri A. Chestakov, Andre T.J.B. Eppink, J J. Ter Meulen, David H. Parker, Mark P.J. Van Der Loo, Gerrit G. Groenenboom, Margaret E. Greenslade, Marsha I. Lester

Chemistry

The photodissociation dynamics of state selected OD radicals has been examined at 243 and 226 nm using velocity map imaging to probe the angle–speed distributions of theD(²S) and O(³P₂) products. Both experiment and complementary first principle calculations demonstrate that photodissociation occurs by promotion of OD from high vibrational levels of the ground X ²Π state to the repulsive 1 ²Σ⁻ state.