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Chemistry Faculty Publications

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Full-Text Articles in Physics

Intercomparison Of Small Unmanned Aircraft System (Suas) Measurements For Atmospheric Science During The Lapse-Rate Campaign, Lindsay Barbieri, Stephan T. Kral, Sean C. C. Bailey, Amy E. Frazier, Jamey D. Jacob, Joachim Reuder, David Brus, Phillip B. Chilson, Christopher Crick, Carrick Detweiler, Abhiram Doddi, Jack Elston, Hosein Foroutan, Javier González-Rocha, Brian R. Greene, Marcelo I. Guzman, Adam L. Houston, Ashraful Islam, Osku Kemppinen, Dale Lawrence, Elizabeth A. Pillar-Little, Shane D. Ross, Michael P. Sama, David G. Schmale Iii, Travis J. Schuyler, Ajay Shankar, Suzanne W. Smith, Sean Waugh, Cory Dixon, Steve Borenstein, Gijs De Boer May 2019

Intercomparison Of Small Unmanned Aircraft System (Suas) Measurements For Atmospheric Science During The Lapse-Rate Campaign, Lindsay Barbieri, Stephan T. Kral, Sean C. C. Bailey, Amy E. Frazier, Jamey D. Jacob, Joachim Reuder, David Brus, Phillip B. Chilson, Christopher Crick, Carrick Detweiler, Abhiram Doddi, Jack Elston, Hosein Foroutan, Javier González-Rocha, Brian R. Greene, Marcelo I. Guzman, Adam L. Houston, Ashraful Islam, Osku Kemppinen, Dale Lawrence, Elizabeth A. Pillar-Little, Shane D. Ross, Michael P. Sama, David G. Schmale Iii, Travis J. Schuyler, Ajay Shankar, Suzanne W. Smith, Sean Waugh, Cory Dixon, Steve Borenstein, Gijs De Boer

Chemistry Faculty Publications

Small unmanned aircraft systems (sUAS) are rapidly transforming atmospheric research. With the advancement of the development and application of these systems, improving knowledge of best practices for accurate measurement is critical for achieving scientific goals. We present results from an intercomparison of atmospheric measurement data from the Lower Atmospheric Process Studies at Elevation—a Remotely piloted Aircraft Team Experiment (LAPSE-RATE) field campaign. We evaluate a total of 38 individual sUAS with 23 unique sensor and platform configurations using a meteorological tower for reference measurements. We assess precision, bias, and time response of sUAS measurements of temperature, humidity, pressure, wind speed ...


Seniority Structure Of 136Xe82, Erin E. Peters, P. Van Isacker, Anagha Chakraborty, Benjamin P. Crider, A. Kumar, S. H. Liu, Marcus T. Mcellistrem, C. V. Mehl, Francisco M. Prados-Estévez, T. J. Ross, J. L. Wood, Steven W. Yates Sep 2018

Seniority Structure Of 136Xe82, Erin E. Peters, P. Van Isacker, Anagha Chakraborty, Benjamin P. Crider, A. Kumar, S. H. Liu, Marcus T. Mcellistrem, C. V. Mehl, Francisco M. Prados-Estévez, T. J. Ross, J. L. Wood, Steven W. Yates

Chemistry Faculty Publications

The level structure of the N = 82 nucleus 136Xe was studied with the inelastic neutron scattering reaction followed by γ-ray detection. A number of the spins and parities were reassigned, and many level lifetimes were determined for the first time using the Doppler-shift attenuation method. New shell-model calculations were also performed using both the full Z = 50–82 model space, and a reduced model space including only the 1d5/2 and 0g7/2 orbitals. This new information characterizing 136Xe was used to identify the seniority structure of the low-lying levels and to assign (π ...


Enhanced Acidity Of Acetic And Pyruvic Acids On The Surface Of Water, Alexis J. Eugene, Elizabeth A. Pillar, Agustín J. Colussi, Marcelo I. Guzman Aug 2018

Enhanced Acidity Of Acetic And Pyruvic Acids On The Surface Of Water, Alexis J. Eugene, Elizabeth A. Pillar, Agustín J. Colussi, Marcelo I. Guzman

Chemistry Faculty Publications

Understanding the acid–base behavior of carboxylic acids on aqueous interfaces is a fundamental issue in nature. Surface processes involving carboxylic acids such as acetic and pyruvic acids play roles in (1) the transport of nutrients through cell membranes, (2) the cycling of metabolites relevant to the origin of life, and (3) the photooxidative processing of biogenic and anthropogenic emissions in aerosols and atmospheric waters. Here, we report that 50% of gaseous acetic acid and pyruvic acid molecules transfer a proton to the surface of water at pH 2.8 and 1.8 units lower than their respective acidity constants ...


Spectroscopy And Formation Of Lanthanum-Hydrocarbon Radicals Formed By C—H And C—C Bond Activation Of 1-Pentene And 2-Pentene, Wenjin Cao, Yuchen Zhang, Silver Nyambo, Dong-Sheng Yang Jul 2018

Spectroscopy And Formation Of Lanthanum-Hydrocarbon Radicals Formed By C—H And C—C Bond Activation Of 1-Pentene And 2-Pentene, Wenjin Cao, Yuchen Zhang, Silver Nyambo, Dong-Sheng Yang

Chemistry Faculty Publications

La atom reactions with 1-pentene and 2-pentene are carried out in a laser-vaporization molecular beam source. The two reactions yield the same metal-hydrocarbon products from the dehydrogenation and carbon–carbon bond cleavage of the pentene molecules. The dehydrogenated species La(C5H8) is the major product, whereas the carbon–carbon bond cleaved species La(C2H2) and La(C3H4) are the minor ones. La(C10H18) is also observed and is presumably formed by La(C5H8) addition to a second pentene molecule. La(C5H8) and ...


Laser-Induced Fluorescence Detection Of The Elusive Sicf Free Radical, Gretchen Rothschopf, Tony C. Smith, Dennis J. Clouthier Jul 2018

Laser-Induced Fluorescence Detection Of The Elusive Sicf Free Radical, Gretchen Rothschopf, Tony C. Smith, Dennis J. Clouthier

Chemistry Faculty Publications

The SiCF free radical has been spectroscopically identified for the first time. The radical was produced in an electric discharge jet using CF3Si(CH3)3 or CF3SiH3 vapor in high pressure argon as the precursor. The laser-induced fluorescence spectrum of the à 2Σ+ 2Π band system in the 610 − 550 nm region was recorded and the 2Π3/2 spin component of the 0—0 band was studied at high resolution. Rotational analysis gave the B values for the combining states, and by fixing the CF bond lengths at ab ...


Spectroscopy And Formation Of Lanthanum-Hydrocarbon Radicals Formed By Association And Carbon-Carbon Bond Cleavage Of Isoprene, Wenjin Cao, Dilkrushi Hewage, Dong-Sheng Yang May 2018

Spectroscopy And Formation Of Lanthanum-Hydrocarbon Radicals Formed By Association And Carbon-Carbon Bond Cleavage Of Isoprene, Wenjin Cao, Dilkrushi Hewage, Dong-Sheng Yang

Chemistry Faculty Publications

La atom reaction with isoprene is carried out in a laser-vaporization molecular beam source. The reaction yields an adduct as the major product and C—C cleaved and dehydrogenated species as the minor ones. La(C5H8), La(C2H2), and La(C3H4) are characterized with mass-analyzed threshold ionization (MATI) spectroscopy and quantum chemical computations. The MATI spectra of all three species exhibit a strong origin band and several weak vibronic bands corresponding to La-ligand stretch and ligand-based bend excitations. La(C5H8) is a five-membered metallacycle, whereas La(C2 ...


Lanthanum-Mediated Dehydrogenation Of Butenes: Spectroscopy And Formation Of La(C4H6) Isomers, Wenjin Cao, Dilkrushi Hewage, Dong-Sheng Yang Jan 2018

Lanthanum-Mediated Dehydrogenation Of Butenes: Spectroscopy And Formation Of La(C4H6) Isomers, Wenjin Cao, Dilkrushi Hewage, Dong-Sheng Yang

Chemistry Faculty Publications

La atom reactions with 1-butene, 2-butene, and isobutene are carried out in a laser-vaporization molecular beam source. The three reactions yield the same La-hydrocarbon products from the dehydrogenation and carbon-carbon bond cleavage and coupling of the butenes. The dehydrogenated species La(C4H6) is the major product, which is characterized with mass-analyzed threshold ionization (MATI) spectroscopy and quantum chemical computations. The MATI spectrum of La(C4H6) produced from the La+1-butene reaction exhibits two band systems, whereas the MATI spectra produced from the La+2-butene and isobutene reactions display only a single band system. Each ...


Detection And Characterization Of The Tin Dihydride (Snh2 And Snd2) Molecule In The Gas Phase, Tony C. Smith, Dennis J. Clouthier Jan 2018

Detection And Characterization Of The Tin Dihydride (Snh2 And Snd2) Molecule In The Gas Phase, Tony C. Smith, Dennis J. Clouthier

Chemistry Faculty Publications

The SnH2 and SnD2 molecules have been detected for the first time in the gas phase by laser-induced fluorescence (LIF) and emission spectroscopic techniques through the Ã1B1–X̃1A1 electronic transition. These reactive species were prepared in a pulsed electric discharge jet using (CH3)4Sn or SnH4/SnD4 precursors diluted in high pressure argon. Transitions to the electronic excited state of the jet-cooled molecules were probed with LIF, and the ground state energy levels were measured from single rovibronic level emission spectra. The LIF spectrum of SnD2 afforded ...


High-Statistics Β+/Ec-Decay Study Of 122Xe, B. Jigmeddorj, P. E. Garrett, C. A. Andreoiu, G. C. Ball, T. Bruhn, D. S. Cross, A. B. Garnsworthy, B. Hadinia, M. Moukaddam, J. Park, J. L. Pore, A. J. Radich, M. M. Rajabali, E. T. Rand, U. Rizwan, C. E. Svensson, P. Voss, Z. Wang, J. L. Wood, Steven W. Yates Oct 2017

High-Statistics Β+/Ec-Decay Study Of 122Xe, B. Jigmeddorj, P. E. Garrett, C. A. Andreoiu, G. C. Ball, T. Bruhn, D. S. Cross, A. B. Garnsworthy, B. Hadinia, M. Moukaddam, J. Park, J. L. Pore, A. J. Radich, M. M. Rajabali, E. T. Rand, U. Rizwan, C. E. Svensson, P. Voss, Z. Wang, J. L. Wood, Steven W. Yates

Chemistry Faculty Publications

Low-lying excited states of 122Xe have been studied via the β+/EC decay of 122Cs with the 8π γ-ray spectrometer at the TRIUMF Isotope Separator and Accelerator facility. The data collected have enabled the observation of new in-band transitions in the excited 0+ state bands. In addition, the 2+ members of the second 0+ and third 0+ state bands have been firmly confirmed by angular correlation analysis.


Opportunities For Undergraduate Research In Nuclear Physics, S. F. Hicks, T. D. Nguyen, D. T. Jackson, S. G. Block, S. T. Byrd, M. T. Nickel, J. R. Vanhoy, Erin E. Peters, Anthony Paul Ramirez, Marcus T. Mcellistrem, Sharmistha Mukhopadhyay, Steven W. Yates Oct 2017

Opportunities For Undergraduate Research In Nuclear Physics, S. F. Hicks, T. D. Nguyen, D. T. Jackson, S. G. Block, S. T. Byrd, M. T. Nickel, J. R. Vanhoy, Erin E. Peters, Anthony Paul Ramirez, Marcus T. Mcellistrem, Sharmistha Mukhopadhyay, Steven W. Yates

Chemistry Faculty Publications

University of Dallas (UD) physics majors are offered a variety of undergraduate research opportunities in nuclear physics through an established program at the University of Kentucky Accelerator Laboratory (UKAL). The 7-MV Model CN Van de Graaff accelerator and the neutron production and detection facilities located there are used by UD students to investigate how neutrons scatter from materials that are important in nuclear energy production and for our basic understanding of how neutrons interact with matter. Recent student projects include modeling of the laboratory using the neutron transport code MCNP to investigate the effectiveness of laboratory shielding, testing the long-term ...


A Stimulated Emission Study Of The Ground State Bending Levels Of Bh2 Through The Barrier To Linearity And Ab Initio Calculations Of Near-Spectroscopic Accuracy, Bing Jin, Dennis J. Clouthier, Riccardo Tarroni Sep 2017

A Stimulated Emission Study Of The Ground State Bending Levels Of Bh2 Through The Barrier To Linearity And Ab Initio Calculations Of Near-Spectroscopic Accuracy, Bing Jin, Dennis J. Clouthier, Riccardo Tarroni

Chemistry Faculty Publications

The ground state bending levels of 11BH2 have been studied experimentally using a combination of low-resolution emission spectroscopy and high-resolution stimulated emission pumping (SEP) measurements. The data encompass the energy range below, through, and above the calculated position of the barrier to linearity. For the bending levels (0,3,0) and above, the data show substantial K-reordering, with the K"a = 1 levels falling well below those with K"a = 0. A comparison of the high-resolution rotationally resolved SEP data to our own very high level ab initio calculations of the rovibronic energy levels shows agreement approaching ...


Lanthanum-Mediated Dehydrogenation Of 1- And 2-Butynes: Spectroscopy And Formation Of La(C4H4) Isomers, Wenjin Cao, Dilrukshi C. Hewage, Dong-Sheng Yang Aug 2017

Lanthanum-Mediated Dehydrogenation Of 1- And 2-Butynes: Spectroscopy And Formation Of La(C4H4) Isomers, Wenjin Cao, Dilrukshi C. Hewage, Dong-Sheng Yang

Chemistry Faculty Publications

La atom reactions with 1-butyne and 2-butyne are carried out in a laser-vaporization molecular beam source. Both reactions yield the same La-hydrocarbon products from the dehydrogenation and carbon-carbon bond cleavage and coupling of the butynes. The dehydrogenated species La(C4H4) is characterized with mass-analyzed threshold ionization (MATI) spectroscopy and quantum chemical computations. The MATI spectra of La(C4H4) produced from the two reactions exhibit two identical transitions, each consisting of a strong origin band and several vibrational intervals. The two transitions are assigned to the ionization of two isomers: La(η4–CH2 ...


Level Lifetimes And The Structure Of 134Xe From Inelastic Neutron Scattering, Erin E. Peters, Anagha Chakraborty, Benjamin P. Crider, S. F. Ashley, E. Elhami, S. F. Hicks, A. Kumar, Marcus T. Mcellistrem, Sharmistha Mukhopadhyay, J. N. Orce, Francisco M. Prados-Estévez, Steven W. Yates Jul 2017

Level Lifetimes And The Structure Of 134Xe From Inelastic Neutron Scattering, Erin E. Peters, Anagha Chakraborty, Benjamin P. Crider, S. F. Ashley, E. Elhami, S. F. Hicks, A. Kumar, Marcus T. Mcellistrem, Sharmistha Mukhopadhyay, J. N. Orce, Francisco M. Prados-Estévez, Steven W. Yates

Chemistry Faculty Publications

The level structure of 134Xe was studied with the inelastic neutron scattering reaction followed by γ-ray detection. A number of level lifetimes were determined for the first time with the Doppler-shift attenuation method and the low-lying excited states were characterized. From this new spectroscopic information, the third excited state, a 0+ level which had only been observed in a previous inelastic neutron scattering study, was verified. Reduced transition probabilities were calculated; comparisons were drawn with a vibrational description of the nucleus and found lacking. The 3 octupole phonon has been confirmed, and the complete negative-parity multiplet resulting from ...


Neutron Scattering Cross Section Measurements For 56Fe, Anthony Paul D. Ramirez, J. Vanhoy, S. F. Hicks, Marcus T. Mcellistrem, Erin E. Peters, Sharmistha Mukhopadhyay, T. D. Harrison, T. J. Howard, D. T. Jackson, P. D. Lenzen, T. D. Nguyen, R. L. Pecha, B. G. Rice, B. K. Thompson, Steven W. Yates Jun 2017

Neutron Scattering Cross Section Measurements For 56Fe, Anthony Paul D. Ramirez, J. Vanhoy, S. F. Hicks, Marcus T. Mcellistrem, Erin E. Peters, Sharmistha Mukhopadhyay, T. D. Harrison, T. J. Howard, D. T. Jackson, P. D. Lenzen, T. D. Nguyen, R. L. Pecha, B. G. Rice, B. K. Thompson, Steven W. Yates

Chemistry Faculty Publications

Elastic and inelastic differential cross sections for neutron scattering from 56Fe have been measured for several incident energies from 1.30 to 7.96 MeV at the University of Kentucky Accelerator Laboratory. Scattered neutrons were detected using a C6D6 liquid scintillation detector using pulse-shape discrimination and time-of-flight techniques. The deduced cross sections have been compared with previously reported data, predictions from evaluation databases ENDF, JENDL, and JEFF, and theoretical calculations performed using different optical model potentials using the TALYS and EMPIRE nuclear reaction codes. The coupled-channel calculations based on the vibrational and soft-rotor models are found ...


Spectroscopy And Formation Of Lanthanum-Hydrocarbon Radicals Formed By C—C Bond Cleavage And Coupling Of Propene, Dilrukshi C. Hewage, Wenjin Cao, Sudesh Kumari, Ruchira Silva, Tao Hong Li, Dong-Sheng Yang May 2017

Spectroscopy And Formation Of Lanthanum-Hydrocarbon Radicals Formed By C—C Bond Cleavage And Coupling Of Propene, Dilrukshi C. Hewage, Wenjin Cao, Sudesh Kumari, Ruchira Silva, Tao Hong Li, Dong-Sheng Yang

Chemistry Faculty Publications

La reaction with propene is carried out in a laser-vaporization molecular beam source. Three La-hydrocarbon radicals are characterized by mass-analyzed threshold ionization (MATI) spectroscopy. One of these radicals is methylenelanthanum [La(CH2)] (Cs), a Schrock-type metal carbene. The other two are a five-membered 1-lanthanacyclopent-3-en [La(CH2CHCHCH2)] (Cs) and a tetrahedron-like trimethylenemethanelanthanum [La(C(CH2)3)] (C3v). Adiabatic ionization energies and metal-ligand stretching and hydrocarbon-based bending frequencies of these species are measured from the MATI spectra, preferred structures and electronic states are identified by comparing the experimental measurements and spectral simulations, and reaction ...


Collective Quadrupole Behavior In 106Pd, Francisco M. Prados-Estévez, Erin E. Peters, A. Chakraborty, M. G. Mynk, D. Bandyopadhyay, N. Boukharouba, S. N. Choudry, Benjamin P. Crider, P. E. Garrett, S. F. Hicks, A. Kumar, S. R. Lesher, C. J. Mckay, Marcus T. Mcellistrem, Sharmistha Mukhopadhyay, J. N. Orce, M. Scheck, J. R. Vanhoy, J. L. Wood, Steven W. Yates Mar 2017

Collective Quadrupole Behavior In 106Pd, Francisco M. Prados-Estévez, Erin E. Peters, A. Chakraborty, M. G. Mynk, D. Bandyopadhyay, N. Boukharouba, S. N. Choudry, Benjamin P. Crider, P. E. Garrett, S. F. Hicks, A. Kumar, S. R. Lesher, C. J. Mckay, Marcus T. Mcellistrem, Sharmistha Mukhopadhyay, J. N. Orce, M. Scheck, J. R. Vanhoy, J. L. Wood, Steven W. Yates

Chemistry Faculty Publications

Excited states in 106Pd were studied with the (n,nγ) reaction, and comprehensive information for excitations with spin ≤6ℏ was obtained. The data include level lifetimes in the femtosecond regime, spins and parities, transition multipolarities, and multipole mixing ratios, which allow the determination of reduced transition probabilities. The E2 decay strength to the low-lying states is mapped up to ≈2.4 MeV in excitation energy. The structures associated with quadrupole collectivity are elucidated and organized into bands.


Mass-Analyzed Threshold Ionization Spectroscopy Of Lanthanum-Hydrocarbon Radicals Formed By C—H Bond Activation Of Propene, Sudesh Kumari, Wenjin Cao, Dilrukshi C. Hewage, Ruchira Silva, Dong-Sheng Yang Feb 2017

Mass-Analyzed Threshold Ionization Spectroscopy Of Lanthanum-Hydrocarbon Radicals Formed By C—H Bond Activation Of Propene, Sudesh Kumari, Wenjin Cao, Dilrukshi C. Hewage, Ruchira Silva, Dong-Sheng Yang

Chemistry Faculty Publications

La(C3H4) and La(C3H6) are observed from the reaction of laser-vaporized La atoms with propene by photoionization time-of-flight mass spectrometry and characterized by mass-analyzed threshold ionization spectroscopy. Two isomers of La(C3H4) are identified as methyl-lanthanacyclopropene [La(CHCCH3)] (Cs) and lanthanacyclobutene [La(CHCHCH2)] (C1); La(C3H6) is determined to be H—La(η3-allyl) (Cs), a C—H bond inserted species. All three metal-hydrocarbon radicals prefer a doublet ground state with a La 6s-based electron configuration. Ionization of the neutral doublet ...


Inelastic Neutron Scattering Cross Section Measurements For 134,136Xe Of Relevance To Neutrinoless Double-Β Decay Searches, Erin E. Peters, T. J. Ross, S. H. Liu, Marcus T. Mcellistrem, Steven W. Yates Jan 2017

Inelastic Neutron Scattering Cross Section Measurements For 134,136Xe Of Relevance To Neutrinoless Double-Β Decay Searches, Erin E. Peters, T. J. Ross, S. H. Liu, Marcus T. Mcellistrem, Steven W. Yates

Chemistry Faculty Publications

Neutrinoless double-β decay (0νββ) searches typically involve large-scale experiments for which backgrounds can be complex. One possible source of background near the 0νββ signature in the observed spectra is γ rays arising from inelastic neutron scattering from the materials composing or surrounding the detector. In relation to searches for the 0νββ of 136Xe to 136Ba, such as the EXO-200 and KamLAND-Zen projects, inelastic neutron scattering γ-ray production cross sections for 136Xe and 134Xe are of importance for characterizing such γ rays that may inhibit the unambiguous identification of this yet-to-be-observed process ...


0+ States In 130,132Xe: A Search For E(5) Behavior, Erin E. Peters, T. J. Ross, S. F. Ashley, Anagha Chakraborty, Benjamin P. Crider, M. D. Hennek, Sinong Liu, Marcus T. Mcellistrem, Sharmistha Mukhopadhyay, Francisco M. Prados-Estévez, Anthony Paul Ramirez, J. S. Thrasher, Steven W. Yates Aug 2016

0+ States In 130,132Xe: A Search For E(5) Behavior, Erin E. Peters, T. J. Ross, S. F. Ashley, Anagha Chakraborty, Benjamin P. Crider, M. D. Hennek, Sinong Liu, Marcus T. Mcellistrem, Sharmistha Mukhopadhyay, Francisco M. Prados-Estévez, Anthony Paul Ramirez, J. S. Thrasher, Steven W. Yates

Chemistry Faculty Publications

The level structures of 130,132Xe were studied with the inelastic neutron scattering reaction followed by γ-ray detection. Level lifetimes were measured using the Doppler-shift attenuation method and low-lying excited states in these nuclei were characterized. With a focus on the decay properties of the 0+ states, these nuclei were examined as representations of the E(5) critical-point symmetry.


An Experimental And Theoretical Study Of Ã2A"Π–X~2A' Band System Of The Jet-Cooled Hbbr/Dbbr Free Radical, Mohammed Gharaibeh, Dennis J. Clouthier, Riccardo Tarroni Jun 2016

An Experimental And Theoretical Study Of Ã2A"Π–X~2A' Band System Of The Jet-Cooled Hbbr/Dbbr Free Radical, Mohammed Gharaibeh, Dennis J. Clouthier, Riccardo Tarroni

Chemistry Faculty Publications

The electronic spectra of the HBBr and DBBr free radicals have been studied in depth. These species were prepared in a pulsed electric discharge jet using a precursor mixture of BBr3 vapor and H2 or D2 in high pressure argon. Transitions to the electronic excited state of the jet-cooled radicals were probed with laser-induced fluorescence and the ground state energy levels were measured from the single vibronic level emission spectra. HBBr has an extensive band system in the red which involves a linear-bent transition between the two Renner-Teller components of what would be a 2Π state ...


Hyperfine Rather Than Spin Splittings Dominate The Fine Structure Of The B 4Σ-X 4Σ- Bands Of Aic, Dennis J. Clouthier, Aimable Kalume Jan 2016

Hyperfine Rather Than Spin Splittings Dominate The Fine Structure Of The B 4Σ-–X 4Σ- Bands Of Aic, Dennis J. Clouthier, Aimable Kalume

Chemistry Faculty Publications

Laser-induced fluorescence and wavelength resolved emission spectra of the B 4ΣX4Σ band system of the gas phase cold aluminum carbide free radical have been obtained using the pulsed discharge jet technique. The radical was produced by electron bombardment of a precursor mixture of trimethylaluminum in high pressure argon. High resolution spectra show that each rotational line of the 0-0 and 1-1 bands of AlC is split into at least three components, with very similar splittings and intensities in both the P- and R-branches. The observed structure was reproduced by assuming bβS magnetic hyperfine coupling ...


Geometric-Phase Interference In A Mn12 Single-Molecule Magnet With Four-Fold Rotational Symmetry, S T. Adams, E H. Da Silva Neto, S Datta, J F. Ware, Christos Lampropoulos, G Christou, Y Myaesoedov, E Zeldov, Jonathan R. Friedman Feb 2013

Geometric-Phase Interference In A Mn12 Single-Molecule Magnet With Four-Fold Rotational Symmetry, S T. Adams, E H. Da Silva Neto, S Datta, J F. Ware, Christos Lampropoulos, G Christou, Y Myaesoedov, E Zeldov, Jonathan R. Friedman

Chemistry Faculty Publications

We study the magnetic relaxation rate Gamma of the single-molecule magnet Mn12-tBuAc as a function of magnetic field component HT transverse to the molecule's easy axis. When the spin is near a magnetic quantum tunneling resonance, we find that Gamma increases abruptly at certain values of HT. These increases are observed just beyond values of HT at which a geometric-phase interference effect suppresses tunneling between two excited energy levels. The effect is washed out by rotating HT away from the spin's hard axis, thereby suppressing the interference effect. Detailed numerical calculations of ...


Water Diffusion In And Out Of The Β-Barrel Of Gfp And The Fast Maturing Fluorescent Protein, Turbogfp, Marc Zimmer, Binsen Li, Ramza Shahid, Paola Peshkepija Jan 2012

Water Diffusion In And Out Of The Β-Barrel Of Gfp And The Fast Maturing Fluorescent Protein, Turbogfp, Marc Zimmer, Binsen Li, Ramza Shahid, Paola Peshkepija

Chemistry Faculty Publications

The chromophore of fluorescent proteins is formed by an internal cyclization of the tripeptide 65SYG67 fragment and a subsequent oxidation. The oxidation is slow – the kinetics of this step is presumably improved in fast maturing GFPs. Water molecules can aid in the chromophore formation. We have used 50ns molecular dynamics simulations of the mature and immature forms of avGFP and TurboGFP to examine the diffusion of water molecules in-and-out of the protein β-barrel. Most crystal structures of GFPs have well-structured waters within hydrogen-bonding distance of Glu222 and Arg96. It has been proposed that they have an important role in chromophore ...


Optical Properties Of Antiferroelectric Cs2nb4o11: Absorption Spectra And First-Principles Calculations, H. L. Liu, C. R. Huang, G. F. Luo, Wai-Ning Mei Nov 2011

Optical Properties Of Antiferroelectric Cs2nb4o11: Absorption Spectra And First-Principles Calculations, H. L. Liu, C. R. Huang, G. F. Luo, Wai-Ning Mei

Chemistry Faculty Publications

We report a joint experimental and theoretical investigation of the optical properties of Cs2Nb4O11. In room temperature optical absorption spectra, we found a direct gap about 3.5560.05 eV and charge transfer excitations at about 4.96 and 6.08 eV, which are in good agreement with the first-principles calculations. Upon passing through the 165 C antiferroelectric to paraelectric phase transition, the peak energies of two charge transfer bands display almost no temperature dependence, yet they become even broader and exhibit enhanced oscillator strength. We infer this intriguing behavior as the manifestation of Nb cation distortions due to the ...


What Is Wrong With Water Barometers?, Dan Sullivan, Robert W. Smith, E. J. Kemnitz, Kevin Barton, Robert M. Graham, Raymond A. Guenther, Larry Webber Jan 2010

What Is Wrong With Water Barometers?, Dan Sullivan, Robert W. Smith, E. J. Kemnitz, Kevin Barton, Robert M. Graham, Raymond A. Guenther, Larry Webber

Chemistry Faculty Publications

Every student who studies atmospheric pressure in physics or chemistry learns the principles behind the construction of barometers. Cistern barometers, such as those found in most laboratories, consist of a long glass tube containing an inverted column of liquid having an open end in a cistern of the liquid. Students learn that the column of liquid is supported by air pressure and is equal in weight to a column of air of the same diameter.


Synthesis Of Magnetic Porous Hollow Silica Nanotubes For Drug Delivery, H. Ma, J. Tarr, M. A. Decoster, J. Mcnamara, D. Caruntu, J. F. Chen, Charles J. O'Connor, Weilie Zhou Mar 2009

Synthesis Of Magnetic Porous Hollow Silica Nanotubes For Drug Delivery, H. Ma, J. Tarr, M. A. Decoster, J. Mcnamara, D. Caruntu, J. F. Chen, Charles J. O'Connor, Weilie Zhou

Chemistry Faculty Publications

In this paper, we report a synthesis of magnetic porous hollow silica nanotubes (MPHSNTs) using sol-gel method. The MPHSNTs were fabricated by coating Fe(3)O(4) nanoparticles and silica on surfactant hexadecyltrimethylammonium bromide (CTAB) modified CaCO(3) nanoneedles surface under alkaline condition. CaCO(3) nanoneedles and surfactant CTAB are introduced as nanotemplates to form the hollow and porous structures, respectively. After removing CTAB by calcination and etching CaCO(3) nanoneedles away in diluted acetic acid, magnetic porous hollow silica nanotubes with Fe(3)O(4) nanoparticles embedded in the silica shell were achieved. The products were characterized by scanning ...


An Extended Multireference Study Of The Electronic States Of Para-Benzyne, Carol A. Parish, Evan B. Wang, Hans Lischka Jul 2008

An Extended Multireference Study Of The Electronic States Of Para-Benzyne, Carol A. Parish, Evan B. Wang, Hans Lischka

Chemistry Faculty Publications

A state-averaged, multireference complete active space (CAS) approach was used for the determination of the vertical excitation energies of valence and Rydberg states of para-benzyne. Orbitals were generated with a 10- and 32-state averaged multiconfigurational self-consistent field approach. Electron correlation was included using multireference configuration interaction with singles and doubles, including the Pople correction for size extensivity, multireference averaged quadratic coupled cluster (MR-AQCC) and MR-AQCC based on linear response theory. There is a very high density of electronic states in this diradical system—there are more than 17 states within 7 eV of the ground state including two 3 ...


Molecular Dynamics Simulations Of Phase Transition In Agno3, Jianjun Liu, Chun-Gang Duan, M. M. Ossowski, Wai-Ning Mei, Robert W. Smith, J. R. Hardy Mar 2002

Molecular Dynamics Simulations Of Phase Transition In Agno3, Jianjun Liu, Chun-Gang Duan, M. M. Ossowski, Wai-Ning Mei, Robert W. Smith, J. R. Hardy

Chemistry Faculty Publications

Structural phase transition in AgNO3 at high temperature is simulated by molecular dynamics. The simulations are based on the potentials calculated from the Gordon–Kim modified electron-gas formalism extended to molecular ionic crystals. AgNO3 transforms into rhombohedral structure at high temperature and the phase transition is associated with the rotations of the NO3 ions and displacements of the NO3 and Ag ions.


Three-Body Analytical Potential For Interacting Helium Atoms, Carol A. Parish, Clifford E. Dykstra Nov 1994

Three-Body Analytical Potential For Interacting Helium Atoms, Carol A. Parish, Clifford E. Dykstra

Chemistry Faculty Publications

Large basis set ab initio calculations have been carried out for a dense grid of points on the He, potential energy surface. Three-body contributions were extracted at every point, and a number of concise functional representations for the three-body potential surface were then examined. Three-body multipolar dispersion terms and other radial and angular terms were used in the representations, and an assessment of relative importance of the different terms is presented. Combined with a two-body He-He potential, the results of this work should offer a high quality interaction potential for simulations of aggregated helium.


Pairwise And Many-Body Contributions To Interaction Potentials In He(N) Clusters, Carol A. Parish, Clifford E. Dykstra Jan 1993

Pairwise And Many-Body Contributions To Interaction Potentials In He(N) Clusters, Carol A. Parish, Clifford E. Dykstra

Chemistry Faculty Publications

High level ab initio calculations have been carried out to assess the pairwise additivity of potentials in the attractive or well regions of the potential surfaces of clusters of helium atoms. A large basis set was employed and calculations were done at the Brueckner orbital coupled cluster level. Differences between calculated potentials for several interacting atoms and the corresponding summed pair potentials reveal the three‐body and certain higher order contributions to the interaction strengths. Attraction between rare gas atoms develops from dispersion, and so helium clusters provide the most workable systems for analyzing nonadditivity of dispersion. The results indicate ...