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The KnowledgeBank at OSU (75.279 recursos)

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

Abstracts of OSU International Symposium on Molecular Spectroscopy 2010-present

Mostrando recursos 1 - 20 de 1.902

  1. A "WET DOG" TUNNELING MOTION AS THE CAUSE FOR THE DOUBLED ROTATIONAL SPECTRUM OF 1-IODONONAFLUOROBUTANE

    Bailey, W. C.; Bohn, R. K.; Grubbs, G. S.; Kisiel, Z.; Cooke, S. A.
    A chirped pulse Fourier transform microwave spectrometer has been used to record the rotational spectra of 1-iodononafluorobutane between 8 GHz and 12 GHz. The target compound was spectroscopically examined as it participated in a supersonic expansion of argon. The spectra recorded are dense owing in part to the small rotational constants, $B$ + $C$ $\approx$ 480 MHz, but also to hyperfine structure generated by the coupling of angular momenta of the iodine nucleus and the rotating molecular frame, e.g. $\mid \chi_{ab} \mid$ $\approx$ 1200 MHz. Notably all of the hyperfine components were observed as doublets. It is postulated that this...

  2. STRUCTURAL STUDIES OF PYRROLE-BENZENE COMPLEXES BY CHIRPED-PULSE ROTATIONAL SPECTROSCOPY

    Lobsiger, Simon; Perez, Cristobal; Zaleski, Daniel P.; Seifert, Nathan A.; Pate, Brooks H.; Pfaffen, Chantal; Trachsel, Maria A.; Leutwyler, Samuel
    Non-covalent intermolecular interactions are important in structural biology. The N-H $\cdots$ $\pi$ hydrogen bond between amino acid side chains is an important structural determinant and highly affects the secondary structure of proteins. The pyrrole-benzene complex can be viewed as a model system for studying these fundamental interactions. Previous IR and UV spectroscopic studies of the pyrrole-benzene complex by Dauster \textit{et al.} nderline{\textbf{10}}, 2827 (2008)} and Pfaffen \textit{et al.} nderline{\textbf{13}}, 14110 (2011)} support a T-shaped structure with an N-H $\cdots$ $\pi$ hydrogen bond to the benzene ring. In order to obtain accurate structural information we have investigated the broadband rotational spectrum...

  3. MW SYSTEMATIC STUDY OF ALKALOIDS: THE DISTORTED TROPANE OF SCOPOLINE

    Ecija, Patricia; Cocinero, Emilio J.; Basterretxea, Francisco J.; Fernandez, Jose A.; Castano, Fernando; Lesarri, Alberto
    Tropane alkaloids have diverse pharmacological uses and are well-known for their neurostimulant activity. Previous structure-activity-relationship established correlations between bioactivity and several aspects of ligand conformation and stereochemistry, including delicate intramolecular effects like nitrogen inversion$^{a}$. We have initiated a series of structural studies on tropane alkaloids$^{b}$, aimed to discerning their intrinsic stereochemical properties using rotational spectroscopy in supersonic jets$^{c}$. Here we extend these studies to the epoxytropanes, initially motivated to interrogate the influence of the epoxy group on nitrogen inversion and ring conformation. The rotational spectrum evidences a single structure in the gas phase, providing a first description of the (three...

  4. GAS-PHASE STRUCTURES OF LINALOOL AND COUMARIN STUDIED BY MICROWAVE SPECTROSCOPY

    Nguyen, H. V. L.; Stahl, W.; Grabow, J.-U.
    The microwave spectra of two natural substances, linalool and coumarin, were recorded in the microwave range from 9 to 16 GHz and 8.5 to 10.5 GHz, respectively.Linalool is an acyclic monoterpene and the main component of lavender oil. It has a structure with many possible conformations. The geometry of the lowest energy conformer has been determined by a combination of microwave spectroscopy and quantum chemical calculations. Surprisingly, a globular rather than a prolate shape was found. This structure is probably stabilized by a $\pi$ interaction between two double bonds which are arranged in two stacked layers of atoms within the...

  5. THE PROTOTYPE DIPEPTIDE GLY-GLY: A ROTATIONAL STUDY

    Varela, M.; Cabezas, C.; Mata, S.; Alonso, J. L.
    The simplest dipeptide Gly-Gly has been examined for the first time in the gas phase by laser ablation molecular beam Fourier transform microwave (LA-MB-FTMW) spectroscopy. The nuclear quadrupole hyperfine structure of two $^{14}$N nuclei has been totally resolved allowing the conclusive identification of three conformers in the supersonic expansion. Intramolecular hydrogen bonding interactions have been analyzed on the bases of the structure of the observed conformers. Present results indicate that it is possible to face the study larger peptides using LA-MB-FTMW spectroscopy.

  6. INFRARED SPECTROSCOPY AND STRUCTURES OF MASS-SELECTED RHODIUM CARBONYL AND RHODIUM DINITROGEN CATIONS

    Abbott, Heather L.; Brathwaite, Antonio D.; Duncan, Michael A.
    Rhodium carbonyl cations, Rh(CO)$_{n}^{+}$, and rhodium dinitrogen cations, Rh(N$_{2})_{n}^{+}$, are produced by laser vaporization in a pulsed-nozzle molecular beam source. Mass-selected infrared photodissociation spectroscopy of these ions and their argon tagged analogs are compared to density functional theory computations. Structures of the rhodium cations are determined based upon the number, frequency position and relative intensity of the infrared active bands between 2000 and 2400 cm$^{-1}$. Computed binding energies and fragmentation patterns suggest that four carbonyl ligands bind strongly to the central rhodium cation.

  7. SLOW ELECTRON VELOCITY-MAP IMAGING OF La$_2$(C$_6$H$_6$) AND La(C$_6$H$_6$)$_2$

    Silva, Ruchira; Yang, Dong-Sheng
    Slow electron velocity-map imaging (SEVI) was used to study the structures and electronic states of La$_2$(C$_6$H$_6$) and La(C$_6$H$_6$)$_2$ complexes formed in a metal cluster beam source. Electron spectra obtained from SEVI have the energy resolution of $\Delta$E/eKE $\approx$ 2$\%$ at eKE=400cm$^{-1}$. The SEVI technique offers much higher data collection efficiency than pulsed-field ionization zero electron kinetic energy spectroscopy. From the SEVI spectra, adiabatic ionization energies were measured to be 32141(5) cm$^{-1}$ for La$_2$(C$_6$H$_6$) and 39033(5) cm$^{-1}$ for La(C$_6$H$_6$)$_2$. The most active vibrational transition for both complexes was identified to be a metal-ligand stretching mode with a frequency of 180 cm$^{-1}$...

  8. UNDERSTANDING COMPLEX SPECTRAL SIGNATURES OF EMBEDDED EXCESS PROTONS IN MOLECULAR SCAFFOLDS WITH THIRD ORDER CORRECTIONS TO THE HARMONIC POTENTIAL SURFACE

    Deblase, Andrew F.; Johnson, Mark A.; Lectka, Thomas; Wang, Xun; Jordan, Kenneth D.; McCoy, Anne B.
    Overtones and combination bands observed in vibrational predissociation spectra of cold ions can often be anticipated by expanding the potential energy surface to third order. This is achieved by relating the third derivatives to the matrix elements that couple the allowed and forbidden states in the harmonic basis. Such a strategy has been successful in predicting Fermi resonances in formic acid clusters and some charged H-bonded complexes. Furthermore, third order couplings have been used to develop a vibrational adiabatic model in which excitation of a bright state is distributed over a Franck-Condon envelop of a lower energy mode, such as...

  9. HIGH-RESOLUTION PHOTOELECTRON SPECTROSCOPY OF 2-BUTYNE

    Jacovella, Ugo; Gans, Berenger; Merkt, Frederic
    Using a coherent narrow-band vacuum-ultraviolet (VUV) laser source (bandwitdh of 0.008~cm$^{-1}$)$ \textbf{71}, 4023 (2000).}$ coupled to a photoionization and pulse-field-ionization zero-kinetic-energy photoelectron (PFI-ZEKE) spectrometer, the threshold photoionization of polyatomic molecules can be studied at high resolution. We present a new measurement of the PFI-ZEKE photoelectron spectrum of the origin band of the X$^+$~$^2$E$_{2(d)}$ $\leftarrow$~X~$^1\mathrm{A}_{1(s)}$ ionizing transition of 2-butyne at a resolution of 0.15~cm$^{-1}$. Despite this high resolution, the spectral congestion originating from the combined effects of the internal rotation, the spin-orbit coupling and the Jahn-Teller effect prevented the full resolution of the rotational structure of the photoelectron spectrum. Combined with...

  10. C-C BOND ACTIVATION AND COUPLING OF PROPENE INDUCED BY LA ATOM

    Hewage, Dilrukshi; Tao, Hong; Silva, Ruchira; Kumari, Sudesh; Yang, Dong-Sheng
    A series of La(C$_n$H$_m$) complexes with n $\leq$ 6 and m $\leq$ 12 were produced by the reactions between propene and La in a supersonic molecular beam source. Their formation and structures were investigated using mass-analyzed threshold ionization (MATI) spectroscopy in combination with theoretical calculations. Previously, we identified the formation of La(C$_3$H$_4$) and H-La(C$_3$H$_5$) through dehydrogenation and metal insertion mechanisms. In this work, we will discuss the formation of La(CH$_2$) and La(C$_4$H$_6$) by La induced C-C bond activation and coupling. La(CH$_2$) is formed by the C-C bond breakage and 1,2-hydride shift of propene and is a Schrock-type carbene complex. This...

  11. TORSION-ROTATION-VIBRATION EFFECTS IN THE $\nu_{20}$, 2$\nu_{21}$, 2$\nu_{13}$ AND $\nu_{21} + \nu_{13}$ STATES OF CH$_3$CH$_2$CN

    Daly, Adam M.; Pearson, John C.; Yu, Shanshan; Drouin, Brian J.; Bermudez, C.; Alonso, J. L.
    Ethyl cyanide, CH$_3$CH$_2$CN, is a highly abundant molecule in hot cores associated with massive star formation where temperatures often approach 200K. Astrophysicists would like to use the many thousands of observed lines to evaluate thermal equilibrium, temperature distributions, heating sources, and radiative pumping effects. In spite of a recent partial success in characterizing the $\nu_{20}$ and $\nu_{12}$ vibrational states~(2013) in press.}, many aspects of the spectroscopy of the $\nu_{20}$ state are not adequately characterized. Torsional splittings in the b-type spectrum of $\nu_{20}$ are typically a few MHz and many a-type transitions also show resolved torsional splittings, both are incompatible with...

  12. MASS ANALYZED THRESHOLD IONIZATION OF LUTETIUM DIMER

    Wu, Lu; Roudjane, Mourad; Liu, Yang; Yang, Dong-Sheng
    Lu$_2$ is produced in a pulsed laser-vaporization metal-cluster source and studied by mass-analyzed threshold ionization (MATI) spectroscopy. The MATI spectrum displays several long progressions from the transitions between various vibrational levels of the neutral and ion electronic states. From the spectrum, the upper limit of the ionization energy of the dimer is determined to be 43996 cm$^{-1}$, and the vibrational frequencies are measured to be 121 cm$^{-1}$ in the neutral state and 90 cm$^{-1}$ in the ion state. By combining with ab initio calculations at CASPT2 level, the ground state of Lu$_2$ is identified as $^3\Sigma_g^-$. The $^3\Sigma_g^-$ state has...

  13. THE CORONENE VIBRONIC STATES ABOVE THE FIRST IONIZATION POTENTIAL INVESTIGATED THROUGH TPEPICO EXPERIMENTS

    Brechignac, Ph.; Falvo, C.; Parneix, P.; Pino, T.; Pirali, O.; Garcia, G.; Nahon, L.; Joblin, C.; Kokkin, D.; Bonammy, A.; Mulas, G.
    Threshold Photoelectron spectra (TPES), as well as Total Ion Yeld (TIY) spectra of jet-cooled Coronene ($C_{12}H_{24}$) have been obtained using the electron/ion coincidence imaging spectrometer DELICIOUS II available at the DESIRS beamline of the French Synchrotron facility SOLEIL. The obtained data can be interpreted in the light of new theoretical DFT and TDDFT based calculations. They will be discussed in comparison to available photoelectron (PES) and optical absorption data. New autoionizing neutral states have also been observed and their relaxation to final cationic states characterized.

  14. UBIQUITOUS INTERSTELLAR MOLECULES WITH RADICALLY DIFFERENT CATION STRUCTURES: INFRARED SPECTROSCOPY OF FORMALDEHYDE AND METHANOL CATIONS

    Mosley, Jonathan D.; Duncan, Michael A.
    Formaldehyde and methanol are detected in interstellar and circumstellar sources by rotational transitions resulting from their well-known structures. For the radical cations with nominal formulas $[C,H_2,O]^+$ and $[C,H_4,O]^+$, no such measurements have been made in interstellar sources or in the laboratory to our knowledge. We measured the infrared spectrum of both radical cations in the gas phase using infrared photodissociation spectroscopy and found structures that differ drastically from the neutral closed shell species. For the case of $[C,H_2,O]^+$, formaldehyde cation $CH_2O^+$ and hydroxymethylene cation $CHOH^+$ are predicted to be minima with only ~5 kcal/mol difference in stability. We see evidence...

  15. INFRARED SPECTROSCOPY OF THE MASS 43 CATION: ACETYL CATION AND PROTONATED KETENE

    Mosley, Jonathan D.; Duncan, Michael A.
    The mass 43 cation $[C_2,H_3,O]^+$ is prominent in mass spectra of organic molecules. Theory predicts no less than nine structural isomers, and the acetyl cation $CH_3CO^+$ is the global minimum. The infrared spectrum of the mass 43 cation from methyl acetate shows vibrations only from the acetyl cation. The effects of the methyl free internal rotor are discussed. The mass 43 cation from acetone shows evidence for both the acetyl cation and the less thermodynamically stable (~50 kcal/mol) protonated ketene isomer $CH_2COH^+$. The effects of varying the kinetic trapping conditions in our ion source on isomeric ratios of the mass...

  16. HIGH PRECISION SPECTROSCOPY OF CH$_5^+$ USING NICE-OHVMS

    Hodges, James N.; Perry, Adam J.; McCall, Benjamin J.
    The elusive methonium ion, CH$_5^+$, is of great interest due to its highly fluxional nature. The only published high-resolution infrared spectrum remains completely unassigned to this date. (1999) \textbf{284}, 135--137. } The primary challenge in understanding the CH$_5^+$ spectrum is that traditional spectroscopic approaches rely on a molecule having only small (or even large) amplitude motions about a well-defined reference geometry, and this is not the case with CH$_5^+$. \vspace{1em} We are in the process of re-scanning Oka's spectrum, in the original Black Widow discharge cell, using the new technique of Noise Immune Cavity Enhanced Optical Heterodyne Velocity Modulation Spectroscopy...

  17. SUB-DOPPLER SPECTROSCOPY OF H$_3^+$

    Hodges, James N.; Perry, Adam J.; Siller, Brian M.; McCall, Benjamin J.
    Spectroscopy of H$_3^+$ is of fundamental interest for advancing \textit{ab initio} efforts to calculate spectra with high precision and accuracy. H$_3^+$ is the simplest polyatomic ion, which is why it is an excellent benchmark for theory. In order to perform calculations with spectroscopic accuracy, relativistic and non-adiabatic corrections to the Born-Oppenhiemer approximation must be included; calculations with these considerations agree to within hundredths of a wavenumber. (1999), \textbf{110}, 5056--5064.} Increasing the precision of the calculations further will require a treatment of quantum electrodynamic effects, as has already been implemented for the diatomic case, \emph{J. Chem. Theor. Comp.} (2011), \textbf{7}, 3105--3115.}...

  18. PRECISION LASER SPECTROSCOPY OF H$_3^+$

    Chen, Hsuan-Chen; Peng, Jin-Long; Amano, T.; Shy, Jow-Tsong
    The high-resolution sub-Doppler Lamb dips of the $\nu_2$ fundamental band transitions of H$_3^+$ have been observed using an extended negative glow discharge tube as an ion source and a periodically poled lithium niobate optical parametric oscillator as a radiation source.,{~\bf 109},~263002~(2012)} The absolute frequencies of five transitions were measured to an accuracy of 250 kHz using a fiber optical frequency comb. In addition, we measured the homogeneous linewidths of these lines. Physical significance of these results will be discussed in terms of collisional processes.

  19. INFRARED SPECTROSCOPY OF JET COOLED ND$_2$H$_2^{+}$ MOLECULAR IONS: THE SYMMETRIC AND ANTISYMMETRIC NH STRETCH MODES

    Chang, Chih-Hsuan; Nesbitt, David J.
    Rovibrational progressions in the symmetric ($v$$_6$) and antisymmetric ($v$$_1$) NH stretching modes of the ND$_2$H$_2^{+}$ molecular ion are observed for the first time, exploiting the i) high ion density and ii) high resolution capabilities of our slit jet discharge infrared spectrometer. These isotopomeric ions are generated by striking a modulated (50 KHz) electrical discharge in a mixture of ND$_3$/H$_2$O/H$_2$ gases, achieving a modulated ion density suitable for time-gated, lock-in detection in the throat of a long path slit-jet expansion. Assignment of both $b$-type and $c$-type bands enables high accuracy determination of the rotational constants ($A$$^{\prime\prime}$=4.85598(19), $B$$^{\prime\prime}$=3.96811(11), and $C$$^{\prime\prime}$=3.44661(40) cm$^{-1}$), with...

  20. SUB-DOPPLER SPECTROSCOPY OF ND$_3$H$^{+}$ ION IN THE NH STRETCHING MODE

    Chang, Chih-Hsuan; Buckingham, Grant T.; Nesbitt, David J.
    Despite early successes with velocity modulation spectroscopy$^{,}$of ammonium (NH$_4^{+}$ ) and perdeuteroammonium (ND$_4^{+}$) cation, corresponding studies of any of the mixed H/D isotopomers (NH$_m$D$_{4-m}^{+}$) have proven elusive. In this talk, we present first high resolution results on the lone NH stretch fundamental mode for the jet cooled ND$_3$H$^{+}$ ion, based on tunable IR difference frequency absorption spectroscopy in a slit jet, sub-Doppler resolution infrared spectrometer. Supersonically cooled ND$_3$H$^{+}$ ions are generated by modulated (50 KHz) discharges (650V, 500 mA) in ND$_3$ doped H$_2$/Ne slit jet expansions, monitored by time-gated, lock-in detection methods and with absorption sensitivities near the quantum shot...

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