Search Results - (Author, Cooperation:L. M. Ziurys)

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  1. 1
    Staff View
    Publication Date:
    2016-01-20
    Publisher:
    American Association for the Advancement of Science (AAAS)
    Print ISSN:
    0036-8075
    Electronic ISSN:
    1095-9203
    Topics:
    Biology
    Chemistry and Pharmacology
    Computer Science
    Medicine
    Natural Sciences in General
    Physics
    Published by:
    http://www.aaas.org/

    Latest Papers from Table of Contents or Articles in Press
  2. 2
    Staff View
    Publication Date:
    2012-09-29
    Publisher:
    American Association for the Advancement of Science (AAAS)
    Print ISSN:
    0036-8075
    Electronic ISSN:
    1095-9203
    Topics:
    Biology
    Chemistry and Pharmacology
    Computer Science
    Medicine
    Natural Sciences in General
    Physics
    Published by:
    http://www.aaas.org/

    Latest Papers from Table of Contents or Articles in Press
  3. 3
    Ziurys, L. M. ; Barclay, W. L. ; Anderson, M. A. ; Fletcher, D. A. ; Lamb, J. W.

    [S.l.] : American Institute of Physics (AIP)
    Published 1994
    Staff View
    ISSN:
    1089-7623
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Electrical Engineering, Measurement and Control Technology
    Notes:
    A design is presented for a millimeter/submillimeter direct absorption spectrometer for studies of the pure rotational spectra of metal-bearing free radicals. The spectrometer operates in the frequency range of 65–550 GHz with an instrumental resolution of 200–1000 kHz and an absorption sensitivity of a few ppm. The instrument utilizes phase-locked Gunn oscillators as the tunable, coherent source of radiation from 65–140 GHz. Higher source frequencies are obtained with Schottky diode multipliers. The gas cell and optics path are designed utilizing Gaussian beam optics to achieve maximum interaction between molecules and the mm-wave radiation in the reaction region. Scalar feedhorns and a series of PTFE lenses are used to propagate the source signal. The gas cell is a cylindrical tube 0.5 m in length with a detachable Broida-type oven. The detector for the spectrometer is a helium-cooled InSb hot electron bolometer. Phase-sensitive detection is achieved by FM modulation of the Gunn oscillators and use of a lock-in amplifier. Spectra are recorded by electrical tuning of the Gunn oscillator, which is done under computer control. The millimeter and sub-mm rotational spectra of several free radicals have been observed for the first time using this instrument, including CaOH, MgOH, CaH, MgF, and BaOH.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.1144885

    Articles: DFG German National Licenses
  4. 4
    Nuccio, B. P. ; Apponi, A. J. ; Ziurys, L. M.

    College Park, Md. : American Institute of Physics (AIP)
    Published 1995
    Staff View
    ISSN:
    1089-7690
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Chemistry and Pharmacology
    Notes:
    Pure rotational spectra of CaOD and MgOD have been recorded in the range 200–390 GHz using millimeter/sub-mm direct absorption spectroscopy. Transitions arising from the (000), (010), (020), and (100) modes have been measured for the 2Σ+ ground electronic states of these free radicals. The data were analyzed successfully using a linear 2Σ+ model for CaOD; for MgOD, only the (000) and (010) states could be fit with this Hamiltonian. Moreover, the (010) data required the addition of a substantial pΠ term to account for contamination of excited 2Π electronic states. For both species, the α2 vibration–rotation term was found to be negative, in contrast to MgOH and CaOH, suggesting a less anharmonic contribution to the bending potential in CaOD and MgOD. These measurements also indicate a shorter O–H bond in MgOH than the other alkaline earth hydroxide radicals, which likely results because this species is quasilinear. © 1995 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.470030

    Articles: DFG German National Licenses
  5. 5
    Fletcher, D. A. ; Anderson, M. A. ; Barclay, W. L. ; Ziurys, L. M.

    College Park, Md. : American Institute of Physics (AIP)
    Published 1995
    Staff View
    ISSN:
    1089-7690
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Chemistry and Pharmacology
    Notes:
    Pure rotational spectra of the alkaline-earth monohydroxides have been recorded for vibrationally excited states (0 1 0), (0 2 0), (0 3 0), and (1 0 0) of the ground electronic state (X 2Σ+) using millimeter-wave absorption spectroscopy. The radicals MgOH, CaOH, SrOH, and BaOH were studied. The data for CaOH, SrOH, and BaOH were analyzed with a linear 2Σ+ model, but with the addition of two terms to account for contamination of the v2=1 2Π and v2=2 2Δ vibronic levels with 2Π and 2Δ electronic states. The data for MgOH, however, did not fit well to this linear model and is additional evidence that this species is quasilinear. © 1995 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.469482

    Articles: DFG German National Licenses
  6. 6
    Anderson, M. A. ; Allen, M. D. ; Ziurys, L. M.

    College Park, Md. : American Institute of Physics (AIP)
    Published 1994
    Staff View
    ISSN:
    1089-7690
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Chemistry and Pharmacology
    Notes:
    The pure rotational spectrum of the MgF radical in its ground electronic state (X 2Σ+) has been recorded using millimeter/submillimeter direct absorption techniques. Transitions arising from the v=0, 1, 2, and 3 vibrational modes of the main magnesium isotopic species, 24MgF, have been observed. In addition, spectra of the isotopomers 26MgF and 25MgF in the natural abundances of magnesium have been detected. Rotational and fine structure constants have been determined for these species, as well as hyperfine parameters for the fluorine nucleus (I=1/2). For 25MgF, the hyperfine structure was also resolved arising from the magnesium nucleus, which has I=5/2, yielding the 25Mg hyperfine and quadrupole constants. Comparison of these hyperfine parameters with those of the heavier alkaline–earth monofluorides and the free 25Mg+ atom suggests that there is an increase in covalent bonding in MgF vs its heavier fluoride counterparts. This behavior is also apparent in the hybridization of the wave function of the unpaired electron in MgF, which appears to consist of almost equal s and p character.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.466565

    Articles: DFG German National Licenses
  7. 7
    Brewster, M. A. ; Ziurys, L. M.

    College Park, Md. : American Institute of Physics (AIP)
    Published 2000
    Staff View
    ISSN:
    1089-7690
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Chemistry and Pharmacology
    Notes:
    The pure rotational spectrum of CaNH2 in its X˜ 2A1 ground electronic state has been recorded using millimeter/submillimeter direct absorption methods in the frequency range 320–537 GHz as well as that of CaND2. The species were created by Broida-oven techniques. Eleven rotational transitions were observed arising from the v=0 and v6=1 states of CaNH2, and eight transitions were recorded for the v3=1 and v4=1 levels. For CaND2, eight transitions (v=0) were also measured. For the majority of these transitions, Ka doublets corresponding to Ka=0–5 were observed and fine structure splittings were resolved in every component. These spectra were analyzed using an S-reduced Hamiltonian; rotational, centrifugal distortion, and spin–rotation parameters were determined for CaNH2, CaND2, and the three observed vibrationally excited states. An r0 structure has also been calculated. The data are consistent with calcium amide being a planar molecule with C2v symmetry and having predominately ionic bonding, as indicated by previous optical studies. © 2000 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.1286919

    Articles: DFG German National Licenses
  8. 8
    Apponi, A. J. ; Anderson, M. A. ; Ziurys, L. M.

    College Park, Md. : American Institute of Physics (AIP)
    Published 1999
    Staff View
    ISSN:
    1089-7690
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Chemistry and Pharmacology
    Notes:
    Pure rotational spectra of the MgOH and MgOD radicals have been recorded in the v2 bending vibration of their X 2Σ+ ground electronic states using millimeter-wave direct absorption spectroscopy. Multiple rotational transitions arising from the v2l=11, 22, 20, 31, 33, 42, and 44 substates have been measured in the frequency range 240–520 GHz for these species. Both the spin-rotation and l-type doubling interactions have been resolved in the spectra. The complete data sets for MgOH and MgOD have been analyzed using a linear model for the Hamiltonian which takes into account higher order (l=±4) l-type interactions. The global analyses were adequate, but anomalous behavior was apparent in both molecules. In particular, the Bv vs v2 relation was found to be highly nonlinear, large variations in the l-type doubling constant q were observed with vibrational level, and r0, rs, and r˜e structures determined differed substantially. Such findings suggest that MgOH is highly quasilinear, comparable to HNCO. The competition between ionic and covalent bonding is therefore becoming apparent in the lighter alkaline earth hydroxide species. © 1999 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.480455

    Articles: DFG German National Licenses
  9. 9
    Xin, J. ; Ziurys, L. M.

    College Park, Md. : American Institute of Physics (AIP)
    Published 1999
    Staff View
    ISSN:
    1089-7690
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Chemistry and Pharmacology
    Notes:
    The pure rotational spectrum of the KC radical in its X 4Σ− ground state has been recorded using millimeter/submillimeter direct absorption spectroscopy. This study is the first gas phase observation of potassium carbide, and of any alkali metal carbide species. The molecule was produced under d.c. discharge conditions by the reaction of potassium vapor and CH4; the vapor was generated in a Broida-type oven. Eleven rotational transitions were measured for KC in the frequency range 344–515 GHz; fine structure was resolved in every transition, which consisted of a quartet pattern. The data were analyzed using nonlinear least-squares methods in a Hund's case (b) basis, and rotational and fine structure parameters were accurately determined. The third-order contribution to the spin–rotation term was not found necessary for the data fit, although it has been suggested for states of quartet multiplicity and higher. The spin–spin interactions in KC appear to have a significant direct dipolar component. The bond length and electron configuration in KC have also been established, which suggest some covalent character to its bonding. © 1999 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.478367

    Articles: DFG German National Licenses
  10. 10
    Xin, J. ; Ziurys, L. M.

    College Park, Md. : American Institute of Physics (AIP)
    Published 1999
    Staff View
    ISSN:
    1089-7690
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Chemistry and Pharmacology
    Notes:
    High resolution spectroscopic measurements have been carried out for alkali methylidyne radicals. The pure rotational spectra of NaCH and KCH, along with their deuterium isotopomers, have been recorded in the frequency range 328–529 GHz using millimeter/submillimeter direct absorption techniques. These molecules were created in a dc discharge by the reaction of metal vapor and CH4 or CD4. These data indicate that KCH and NaCH are linear molecules with 3Σ− ground electronic states arising from a π2 configuration. Spectroscopic constants for KCH and NaCH have been determined from the data, including rotational, spin–spin, and spin–rotation parameters, as well as bond lengths. In comparison with other alkali and transition metal-bearing molecules, these results suggest some degree of covalent bonding in the alkali methylidynes, with carbon atom undergoing sp hybridization. © 1999 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.478202

    Articles: DFG German National Licenses
  11. 11
    Xin, J. ; Robinson, J. S. ; Apponi, A. J. ; Ziurys, L. M.

    College Park, Md. : American Institute of Physics (AIP)
    Published 1998
    Staff View
    ISSN:
    1089-7690
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Chemistry and Pharmacology
    Notes:
    The pure rotational spectrum of BaCH3(X˜ 2A1) in its ground vibrational state has been recorded using millimeter/submillimeter direct absorption techniques, the first spectroscopic information obtained for this molecule. The radical was created using Broida-type oven/d.c. discharge methods by the reaction of barium vapor and Sn(CH3)4. Twenty-eight rotational transitions of the main isotopomer 138BaCH3 were recorded, as well as five for 136BaCH3 and three for the 137BaCH3 species. Being a prolate symmetric top, K ladder structure was observed in all transitions for BaCH3, as well as fine structure splittings which arise from the unpaired electron in the molecule. For the 137Ba isotopomer, hyperfine interactions were also resolved, arising from the spin of the barium nucleus. The complete data set has been analyzed with a 2A Hamiltonian, and rotational, spin-rotational, and magnetic hyperfine/nuclear quadrupole parameters accurately determined. The fine and hyperfine structure constants established from this study suggest a predominantly ionic bond for BaCH3, but with a considerable covalent component. Structural parameters for BaCH3 derived in this work are consistent with those of other alkaline earth monomethyl species. © 1998 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.475662

    Articles: DFG German National Licenses
  12. 12
    Allen, M. D. ; Ziurys, L. M.

    College Park, Md. : American Institute of Physics (AIP)
    Published 1997
    Staff View
    ISSN:
    1089-7690
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Chemistry and Pharmacology
    Notes:
    The pure rotational spectrum of the FeF radical in its 6Δi ground electronic state has been recorded using millimeter/submillimeter direct absorption techniques. Transitions arising from all six spin-orbit components have been observed in the v=0, 1, and 2 vibrational levels of 56FeF, the main isotopic species, and also in the less abundant 54Fe isotopomer. Hyperfine splittings, arising from the 19F nuclear spin of I=1/2, were resolved in the majority of transitions recorded, and lambda-doubling interactions were observed in the Ω=3/2, 1/2, and −1/2 spin-orbit ladders. The complete data set has been analyzed using a 6Δ Hamiltonian, and rotational, spin-orbit, spin–spin, lambda-doubling, and hyperfine constants determined. This study has conclusively demonstrated that the ground electronic state of FeF is 6Δi. It also suggests that FeF has more covalent character to its bonding than alkaline earth or alkali metal counterparts. © 1997 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.473446

    Articles: DFG German National Licenses
  13. 13
    Sheridan, P. M. ; Xin, J. ; Ziurys, L. M.

    College Park, Md. : American Institute of Physics (AIP)
    Published 2002
    Staff View
    ISSN:
    1089-7690
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Chemistry and Pharmacology
    Notes:
    The rotational spectrum of the NaC radical in the v=0 level of its X 4Σ− state has been recorded using millimeter/submillimeter-wave absorption spectroscopy. This work is the first spectroscopic observation of this species. The molecule was generated under dc discharge conditions by the reaction of sodium vapor with methane; the vapor was generated in a Broida oven. Thirteen rotational transitions were measured in the frequency range from 231 (N=9←8) to 539 GHz (N=21←20). The quartet fine structure was partially resolved for each transition. The rotational transition frequencies were modeled with an effective Hamiltonian. An ambiguity in the fitting procedure produced two alternative values of the spin–spin coupling constant λ, one large and the other small in magnitude. A simple theoretical estimate of this parameter, based on atomic orbitals on the C− atom, suggests that the latter fit is the correct solution to the problem. The same ambiguity occurs in the fit of the rotational spectrum of KC in its X 4Σ− state published earlier [Xin and Ziurys, J. Chem. Phys. 110, 4797 (1999)]. The revised, preferred fit of the data is given in this paper. © 2002 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.1457441

    Articles: DFG German National Licenses
  14. 14
    Halfen, D. T. ; Apponi, A. J. ; Thompsen, J. M. ; Ziurys, L. M.

    College Park, Md. : American Institute of Physics (AIP)
    Published 2001
    Staff View
    ISSN:
    1089-7690
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Chemistry and Pharmacology
    Notes:
    The pure rotational spectrum of the SrSH radical in its ground electronic (X˜ 2A′) and vibrational states has been measured using millimeter/submillimeter-wave direct absorption techniques. This work is the first observation of SrSH with rotational resolution. The spectrum of its deuterium isotopomer SrSD and SrS (X 1Σ+) has been recorded as well. These species were created by the reaction of strontium vapor and H2S, in the presence of a dc discharge. SrS was also made with CS2. For SrSH and SrSD, eight rotational transitions were recorded, respectively, for which asymmetry components up to Ka=8 were measured; fine structure was also resolved in each component. Thirteen transitions of SrS in each of its v=0, 1, and 2 states have additionally been observed. These data have been analyzed and spectroscopic parameters determined for all three species, including spin-rotation terms for the strontium hydrosulfides. From an r0 structure calculation, the bond angle in SrSH was determined to be 91.48(3)°, very close to that of H2S and CaSH. This geometry indicates that SrSH is a covalently bonded molecule, as opposed to linear (and ionic) SrOH. The Sr–S bond length in SrSH was also found to be greater than that of SrS (rSr—S=2.705 Å versus 2.441 Å), indicating a change in bond order. In addition, the spin-rotation interaction in SrSH and SrSD includes a small contribution from the off-diagonal term, (cursive-epsilonab+cursive-epsilonba)/2, resulting from the crossing of energy levels with ΔJ=0, ΔKa=±1. Second-order spin-orbit coupling appears to make a significant contribution to the spin-rotation splitting, as well, which must arise from mixing of the A˜ 2A′ and B˜ 2A″ excited states. © 2001 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.1419060

    Articles: DFG German National Licenses
  15. 15
    Milam, S. N. ; Apponi, A. J. ; Woolf, N. J. ; Ziurys, L. M.

    [s.l.] : Nature Publishing Group
    Published 2007
    Staff View
    ISSN:
    1476-4687
    Source:
    Nature Archives 1869 - 2009
    Topics:
    Biology
    Chemistry and Pharmacology
    Medicine
    Natural Sciences in General
    Physics
    Notes:
    [Auszug] The interstellar medium is enriched primarily by matter ejected from old, evolved stars. The outflows from these stars create spherical envelopes, which foster gas-phase chemistry. The chemical complexity in circumstellar shells was originally thought to be dominated by the elemental carbon ...
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1038/nature05905

    Articles: DFG German National Licenses