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The KnowledgeBank at OSU (76.127 recursos)

Knowledge Bank contains collections of presentations, publications and reports related to Ohio State University.

Abstracts of OSU International Symposium on Molecular Spectroscopy 2000-present

Mostrando recursos 1 - 20 de 4.203

  1. HIGH RESOLUTION ELECTRONIC SPECTROSCOPY OF THE ARGON VAN DER WAALS COMPLEXES OF 1, 2, 3, 6, 7, 8-HEXAHYDROPYRENE IN THE GAS PHASE.

    Morgan, Philip J.; Fleisher, Adam J.; Roscioli, Joseph R.; Pratt, David W.
    The study of van der Waals complexes provides structural and dynamical information about the weak chemical forces that exist between aromatic molecules and rare gas atoms. In this report, we describe the rotationally resolved fluorescence excitation spectra of the S$_1$$\leftarrow$S$_0$ origin bands of the single argon atom complexes of 1, 2, 3, 6, 7, 8-hexahydropyrene. Analysis of the spectra provides information about the geometries of both conformers of the bare molecule and their argon complexes in both electronic states. The equilibrium positions of the argon atom in both conformers will be discussed.

  2. HIGH RESOLUTION INVESTIGATION OF SILACYCLOBUTANE USING FTMW AND SYNCHROTRON BASED FTIR SPECTROSCOPY

    Dijk, Cody Van; Nest, Samantha Van; Chen, Ziqiu; Wijngaarden, Jennifer Van
    The rotational spectrum of silacyclobutane (c-C${_3}$H${_8}$Si) has been measured between 8 and 24 GHz using Fourier transform microwave spectroscopy. Although the microwave spectrum was previously reported \underline{\textbf{54}} (4979), 1971.}, the current study is the first observation of tunneling splitting in the ground state due to ring puckering. The observed transitions within each tunneling state obey \textit{a-}type selection rules and \textit{c-}type transitions that connect the inversion states have also been observed. The rotational constants determined were used to model the rotational structure of several vibrational bands of silacyclobutane including the weak ring puckering mode at 157 cm$^{-1}$. The far infared spectrum...

  3. HELIUM DROPLETS AS NANO-CRYOSTATS FOR MOLECULAR SPECTROSCOPY: AGGREGATION, STATE SELECTION AND ELECTRON SPIN RESONANCE

    Ernst, Wolfgang E.
    Droplets of about $10^{4}$ helium atoms generated in a supersonic expansion, represent a nanometer-sized superfluid medium of 0.4 K temperature and can be doped with one or several atoms or molecules that may form complexes in this cold environment. Using two-laser excitation schemes, we were able to identify the alkali trimers K$_3$, Rb$_3$, K$_2$Rb and KRb$_2$ in their lowest quartet states formed on helium droplets loaded with potassium and rubidium atoms and assign several excited states that underlie both Jahn-Teller and spin-orbit coupling. As helium provides a gentle and only weakly perturbing matrix, it appeared desirable to look for ways...

  4. INFRARED VACUUM ULTRAVIOLET SPECTROSCOPY OF ALLYL RADICAL

    Reed, B.; Lam, C. S.; Xing, X.; Lau, K. C.; Ng, C. Y.; Zhang, X.; Vasiliou, A.; Ellison, G. B.
    An infrared (IR)-vacuum ultraviolet (VUV) double resonance experiment on the allyl (CH$_2$CHCH$_2$) radical will be described. The pulsed field ionization-photoelectron (PFI-PE) spectrum of the allyl (CH$_2$CHCH$_2$) radical has already been obtained and used to determine the accurate ionization energy of 65 584.6 +/- 2.0 cm$^{-1}$ (8.131 46 ±0.000 25 eV). Next, building on previous work which identified IR resonances at 3113.98 and 3110.59 cm$^{-1}$, we anticipate the first IR-VUV double resonance spectrum of the allyl (CH$_2$CHCH$_2$) radical. \vspace{1em} We have shown previously that high-resolution IR spectra of polyatomic neutral closed shell molecules can be obtained with high sensitivity by scanning...

  5. MICROWAVE SPECTROSCOPY OF SEVEN CONFORMERS OF 1,2-PROPANEDIOL

    Neill, Justin L.; Muckle, Matt T.; Pate, Brooks H.; Lovas, F. J.; Plusquellic, D. F.; Remijan, A. J.
    Previously, two conformations of 1,2-propanediol have been identified by microwave spectroscopy by Caminati. \textbf{86} (1981) 193-201.} Here we report the assignment of five additional conformers, two from work on a Balle-Flygare type cavity FTMW spectrometer at NIST, operating between 8 and 26 GHz, and three from a deep average scan on the chirped pulse Fourier transform microwave (CP-FTMW) spectrometer at the University of Virginia, operating between 6.5 and 18.5 GHz. All seven of the assigned conformers contain an intramolecular hydrogen bond between the two hydroxyl groups. Stark effect measurements have been performed on the cavity FTMW spectrometer to determine the...

  6. DENSITY FUNCTIONAL THEORY STUDY ON MOLECULAR STRUCTURE AND VIBRATIONAL SPECTRA OF 4-AMINO-1-METHYLBENZENE

    Kumru, M.; Bardakci, T.; Sari, L.
    We have discussed the applicability limits of HF, MP2 and DFT-B3LYP methods on 4-amino-1-methylbenzene in our previous work [1]. We have found the DFT-B3LYP method very promising for vibrational spectral analyses. In this study, we extend DFT calculations with different basis sets for more appropriateness to exprimental results. The optimized molecular structures, vibrational frequencies and coresponding vibrational assigments of 4-amino-1-methylbenzene have been obtained from the DFT-B3LYP, DFT-B3PW91 and DFT-PBEPBE methods implementing the 6-311G+** and aug-ccPVQZ basis sets. Scale factors, which bring computational frequencies in closer agreement with the experimental data, have been calculated for predominant vibrational motions of the normal...

  7. INFRARED SPECTRA OF CARBONYL SULFIDE-ACETYLENE TRIMERS: OCS-(C$_2$H$_2$)$_2$ AND TWO ISOMERS OF (OCS)$_2$-C$_2$H$_2$

    Afshari, Mahin; Dehghany, M.; Oliaee, J. N.; Moazzen-Ahmadi, N.; McKellar, A. R. W.
    Spectra of acetylene-carbonyl sulphide trimers in the region of the OCS \nub{1} fundamental ($\sim$2062 \wn) are observed using a tunable diode laser to probe a pulsed supersonic slit jet expansion. A previous microwave study of (OCS)$_2$- C$_2$H$_2$ by Peebles and Kuczkowski \textbf{111}, 10511 (1999).} gave a nonplanar triangular twisted structure, which could be thought of as a polar OCS dimer plus a C$_2$H$_2$ monomer lying above the dimer plane. In the present work, three infrared bands are analyzed. The first band clearly belongs to this previously known (OCS)$_2$-C$_2$H$_2$ complex. The second band can be assigned as an isomer of (OCS)$_2$-C$_2$H$_2$...

  8. THEORETICAL STUDIES OF TIME-RESOLVED PHOTOELECTRON SPECTRA OF IBr$^-$

    Horvath, Samantha; McCoy, Anne B.; Pitzer, Russell M.
    In the present study, we examine the time-resolved photoelectron spectra of IBr$^-$. In the photodetachment studies performed by Sanov and co-workers and Lineberger and co-workers,}, {\bf{2005}}, {\it{122}}, 174305; Leonid Sheps, Elisa M. Miller, and W. C. Lineberger (private communication).} the anionic species, prepared in its electronic ground state ($^2\Sigma_{1/2}^+$), is excited to either its {\it{\~{A}}}$^\prime$ ($^2\Pi_{3/2}$) or {\it{\~{B}}} ($^2\Sigma_{1/2}^+$) excited state, before electron photodetachment and dissociation on the {\it{\~{C}}} ($^1\Pi_1$) or higher-lying excited states of the neutral species, respectively. In this work, we use the electronic structure program {\it{Columbus}} to calculate the six lowest electronic states of IBr$^-$ and the...

  9. RAYLEIGH SCATTERING CROSS SECTION MEASUREMENTS WITH A THREE MIRROR RING CAVITY

    Kuramoto, Douglas S.; Zare, Richard N.; Kachanov, Alexander A.
    Most optical cavities in cavity ring-down spectroscopy consist of two mirrors. Using a more complicated cavity design, such as one with three mirrors, can lead to advantages such as reducing the effect of baseline variations due to reflections between the cavity mirror and the laser. A three mirror cavity in the ring configuration has been developed which uses the backward traveling wave to provide feedback to an external cavity diode laser. Measurements of Rayleigh scattering cross sections using this setup will be discussed.

  10. INFRARED SPECTRA OF M$^+$(2-AMINO-1-PHENYL ETHANOL)(H$_2$O)$_{n=0-2}$Ar (M=Na, K)

    Nicely, Amy L.; Lisy, James M.
    A balance of competing electrostatic and hydrogen bonding interactions directs the structure of hydrated gas-phase cluster ions. Because of this, a biologically relevant model of cluster structures should include the effects of surrounding water molecules and metal ions such as sodium and potassium, which are found in high concentrations in the bloodstream. The molecule 2-amino-1-phenyl ethanol (APE) serves as a model for the neurotransmitters ephedrine and adrenaline. The neutral APE molecule contains an internal hydrogen bond between the amino and hydroxyl groups. In the M$^+$(APE) complex, the cation can either interrupt the internal hydrogen bond or position itself above the...

  11. THE OPTICAL STARK SPECTRA OF CoF AND CoH

    Wang, Hailing; Zhuang, Xiujuan; Steimle, Timothy C.
    Comparing the predicted and observed permanent electric dipole moments, $\mu$$_{el}$, for simple diatomic cobalt containing molecules is a means of testing computational methodologies used for modeling cobalt-catalyzed reactions. Here we report on the experimental determination of $\mu$$_{el}$ for CoH and CoF from the analysis of the Stark shifts in the (0,0) bands of the $A^{\prime}^{3}$$\Phi_{4}-X^{3}\Phi_{4}$ system of cobalt monohydride, CoH, and the $[18.8]^{3}$$\Phi_{4}-X^{3}\Phi_{4}$ system of cobalt monofluoride, CoF. In addition, the proton magnetic hyperfine interaction in CoH is analyzed. The relative values for $\mu$$_{el}$ are rationalized using a molecular orbital correlation diagram and with high-level \textit {ab initio} predictions\underline {\textbf{126}}...

  12. HOONO ISOMERIZATION TO HONO$_2$ INVOLVING CONICAL INTERSECTIONS

    Kumar, T. J. Dhilip; Stanton, John F.; Barker, John R.
    The important atmospheric reactions HO$_2$ + NO and OH + NO$_2$ lead to formation and dissociation of the cis- and trans- isomers of the HOONO complex. In the present work, the global HNO$_3$ potential energy surface (PES) is being studied by using high-level ab initio electronic structure methods. This PES, 3999 (2003).} and others in the same class have been studied previously by others. In the F + NO$_2$ reaction system, UCCSD(T) calculations showed that FONO isomerizes to FNO$_2$ through a tight transition state involving a two-state avoided curve crossing, 7639 (2004).}. A similar mechanism has been invoked for HOONO,...

  13. MULTI-STATE VIBRONIC INTERACTIONS IN FLUORINATED BENZENE RADICAL CATIONS.

    Faraji, S.; Koppel, H.
    \maketitle Conical intersections of potential energy surfaces have emerged as paradigms for signalling strong nonadiabatic coupling effects . An important class of systems where some of these effects have been analyzed in the literature, are the benzene and benzenoid cations, where the electronic structure, spectroscopy, and dynamics have received great attention in the literature. In the present work a brief overview is given over our theoretical treatments of multi-mode and multi-state vibronic interactions in the benzene radical cation and some of its fluorinated derivatives. The fluorobenzene derivatives are of systematic interest for at least two different reasons. (1) The reduction...

  14. DETECTION OF IODINE MONOXIDE RADICALS IN THE MARINE BOUNDARY LAYER USING AN OPEN-PATH CAVITY RING-DOWN SPECTROMETER

    Wada, Ryuichi; Beames, Joseph M.; Orr-Ewing, Andrew J.
    An open-path cavity ring down spectroscopy (CRDS) instrument for measurement of atmospheric iodine monoxide (IO) radicals has been tested in the laboratory and subsequently deployed in Roscoff as part of the Reactive Halogens in the Marine Boundary Layer (RHaMBLe) project in September 2006. In situ measurements are reported of local IO mixing ratios in the marine boundary layer. \underline{\textbf{58}}, 69, 2007.} The absorption cross section at the bandhead of the IO A$^2\Pi_{3/2}$ - X$^2\Pi_{3/2}$ (3,0) vibronic band was used to obtain the mixing ratios of atmospheric IO. The mixing ratios of IO were obtained on two days, peaked close to...

  15. HIGH-RESOLUTION SPECTROSCOPY OF {$n$p} RYDBERG STATES OF He$_2$: 1. RYDBERG-STATE-RESOLVED THRESHOLD IONIZATION SPECTRA OF METASTABLE He$_2$

    Liu, Jinjun; Sprecher, Daniel; Raunhardt, Matthias; Schafer, Martin; Merkt, Frederic
    A supersonic beam of metastable He$_2^*$ a $^3\Sigma_{\rm u}^+$ molecules was generated using a pulsed discharge at the exit of a pulsed valve prior to the gas expansion into vacuum.% , \emph{J. Chem. Phys.} \textbf{128}, 164310 (2008).} Transitions to high $n$p Rydberg states were recorded using photoionization and Rydberg-state-resolved threshold ionization spectroscopy.% , \emph{Chem. Phys. Lett.} \textbf{346}, 201 (2001).} Overview scans at moderate resolution (0.3 cm$^{-1}$) were obtained with ionization fields ranging from 1.3 to 133 V/cm, lowering the ionization thresholds by 5.5 and 55 cm$^{-1}$, respectively. Using a solid-state UV laser system% , \emph{Rev. Sci. Instr.} \textbf{76}, 103103 (2005).}...

  16. LABORATORY MEASUREMENT OF THE CO CAMERON BANDS AND VISIBLE EMISSIONS FOLLOWING VUV PHOTODISSOCIATION OF CO${_2}

    Kalogerakis, K. S.; Romanescu, C.; Slanger, T. G.; Lee, L. C.; Ahmed, M.; Wilson, K. R.
    The CO($\textit{a}^{3}$\Pi-$\textit{X}^{1}$$\Sigma^{+}$) Cameron bands are one of the most important emission features in the UV dayglow of the CO${_2}$ planets, as demonstrated in the case of Mars by the measurements performed by Mariner and Mars Express missions. One of the mechanisms to produce electronically excited CO($\textit{a}$^{3}\Pi$) is photodissociation of CO${_2}$ at wavelengths shorter than 108 nm. At wavelengths below 100 nm, new CO${_2}$ photodissociation channels open leading to formation of higher energy triplet states of CO. These states cascade into the lower triplet state by emission in the visible spectral region before radiating in the Cameron system. This two step...

  17. MEASUREMENTS OF THE CO$_2$ 15 $\mu$m BAND SYSTEM BROADENED BY AIR, N$_2$ AND CO$_2$ AT TERRESTRIAL ATMOSPHERIC TEMPERATURES

    Smith, M. A. H.; Devi, V. Malathy; Benner, D. Chris; Blake, T. A.; Sams, R. L.
    In earth remote sensing, retrievals of atmospheric temperature profiles are often based on observed radiances in infrared spectral regions where emission from atmospheric CO$_2$ predominates. To achieve improved retrieval accuracy, systematic errors in the forward model must be reduced, especially those associated with errors in the spectroscopic line calculation. We have recorded more than 110 new high-resolution infrared spectra of the 15-$\mu$m band system of CO$_2$ to accurately determine line intensities, self-, air- and N$_2$-broadened widths and pressure-induced line shifts, along with their temperature dependences. The spectra were recorded with the Bruker IFS 120 HR Fourier transform spectrometer at Pacific...

  18. ROTATION AND MATRIX EFFECTS ON THE EPR SPECTRA OF METHYL RADICALS TRAPPED IN GAS SOLIDS

    Dmitriev, Yurij A.; Benetis, Nikolas-Ploutarch
    A study is presented on EPR spectra of methyl radicals, CH$_3$, matrix-isolated in gas solids at liquid helium temperatures. It was shown very recently \underline {\textbf{21}}(10), 103201 March 2009.} that the peculiar features of the trapped methyl rotor are attributed to the quantum effects of inertial rotary motion and its coupling to the nuclear-spin of the radical. Here, we report an investigation of the spectrum saturation behaviour and present a qualitative consideration of the spectrum anisotropy found earlier. However the broadening is by far smaller than in the expected powder of a fully anisotropic radical with rhombic $hf$-interaction and $g$-tensor...

  19. ASTRONOMICAL AND ATMOSPHERIC SPECTROSCOPY IN THE SMM/THz: EXPERIMENTS, ANALYSIS, AND CATALOGS.

    De Lucia, Frank C.
    For many years the needs of the astronomical and atmospheric science communities have directly or indirectly motivated much of the work at this symposium. Interestingly, the power and sophistication of the field instruments have grown at such a rate that the needs for laboratory data seem to be diverging rather than converging. The central role played by catalogs will be discussed, as well as their impact on the spectroscopic community.

  20. INVESTIGATION OF THE AMIDE I BAND OF N-METHYLACETAMIDE IN SOLID PARAHYDROGEN USING FTIR SPECTROSCOPY

    Paulson, Leif O.; Anderson, David T.
    We report the FTIR spectra of the Amide I and Amide A vibrational modes of N-methylacetamide (NMA, CH$_3$CONHCH$_3$) isolated in a solid parahydrogen (pH$_2$) matrix. NMA is one of the simplest molecules that contains the peptide bond and has therefore been the subject of numerous studies, especially those concerning peptide structure and dynamics. Solid pH$_2$ is a unique quantum solid matrix host that, among other features, allows for high-resolution IR studies of trapped dopant species. In our preliminary report, talk R008 (2006)} we showed that the Amide I lineshape was surprisingly broad and shifts were observed with small changes in...

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