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P Thaddeus - One of the best experts on this subject based on the ideXlab platform.
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the Rotational Spectra of 29 sic 2 and 30 sic 2
Astrophysical Journal Supplement Series, 2011Co-Authors: C A Gottlieb, P Thaddeus, Sandra Brunken, Damian L Kokkin, K Young, N A Patel, Michael C MccarthyAbstract:The Rotational Spectra of {sup 29}SiC{sub 2} and {sup 30}SiC{sub 2}, two silicon isotopic species of the abundant astronomical ring {sup 28}SiC{sub 2}, have been characterized in the millimeter band between 140 and 360 GHz in a low pressure discharge through SiH{sub 4}, C{sub 2}H{sub 2}, and Ar. Precise Rotational and centrifugal distortion constants have been derived for both species by fitting a standard asymmetric top Hamiltonian to 38 a-type transitions of {sup 29}SiC{sub 2} and 35 of {sup 30}SiC{sub 2}; the data sets include transitions up to K{sub a} = 8 and at least J = 16. With these new measurements in hand, the most intense radio transitions of both species either have been measured or can now be predicted to better than 1 km s{sup -1} in equivalent radial velocity up to 500 GHz, more than adequate accuracy for Spectral line identifications in circumstellar shells of evolved carbon stars such as IRC+10216 where SiC{sub 2} is conspicuous. More than 10 new lines of {sup 29}SiC{sub 2} and {sup 30}SiC{sub 2} have been identified between 295 and 354 GHz in the interferometric Spectral line survey of IRC+10216 with the Submillimeter Array.
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Rotational Spectra and equilibrium structures of h2sis and si2s
Journal of Chemical Physics, 2011Co-Authors: Michael C Mccarthy, C A Gottlieb, S Thorwirth, P Thaddeus, Jurgen GaussAbstract:The Rotational Spectra of two small silicon sulfides, silanethione H2SiS and the disilicon sulfide ring Si2S, have been detected in the centimeter band by Fourier transform microwave spectroscopy of a molecular beam; lines of H2SiS were also observed in the millimeter band up to 377 GHz in a glow discharge. Precise Rotational and centrifugal distortionconstants have been determined for the normal and a number of the more abundant rare isotopic species of both closed-shell molecules. Theoretical equilibrium (re) structures of H2SiS and Si2S were derived from coupled-cluster calculations that included triple and quadruple excitations, core correlation, and extrapolation to the basis-set limit. The re structures agree to within 5×10−4 A and 0.1∘with empirical equilibrium (re emp ) structures derived from the experimental Rotational constants, combined with theoretical vibrational and electronic corrections. Both H2SiS and Si2S are good candidates for radioastronomical detection in the circumstellar shells of...
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Rotational Spectra of vibrationally excited cch and ccd
Journal of Chemical Physics, 2007Co-Authors: T C Killian, C A Gottlieb, P ThaddeusAbstract:The millimeter-wave Rotational Spectra of the lowest bending and stretching vibrational levels of CCH and CCD were observed in a low pressure discharge through acetylene and helium. The Rotational, centrifugal distortion, and fine structure constants were determined for the (0200) and (0220) bending states, the (100) and (001) stretching levels, and the (011) combination level of CCH. The same pure bending and stretching levels, and the (110) combination level were observed in CCD. Apparent anomalies in the spectroscopic constants in the bending states were shown to be due to l-type resonances. Hyperfine constants, which in CCH are sensitive to the degree of admixture of the AΠ2 excited electronic state, were determined in the excited vibrational levels of both isotopic species. Theoretical Fermi contact and dipole-dipole hyperfine constants calculated by Peric et al. [J. Mol. Spectrosc. 150, 70 (1991)] were found to be in excellent agreement with the measured constants. In CCD, new Rotational lines tenta...
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Rotational Spectra of small pahs acenaphthene acenaphthylene azulene and fluorene
The Astrophysical Journal, 2007Co-Authors: S Thorwirth, P Theule, C A Gottlieb, M C Mccarthy, P ThaddeusAbstract:Pure Rotational Spectra of four small polycyclic aromatic hydrocarbons have been observed by Fourier transform microwave spectroscopy of a molecular beam in the frequency range from 7 to 37 GHz. Initial searches for acenaphthene (C12H10), acenaphthylene (C12H8), and fluorene (C13H10) were guided by quantum chemical calculations performed at the B3LYP/cc-pVTZ level of theory. All three molecules exhibit b-type Rotational Spectra and are calculated to be moderately polar, with dipole moments of 0.3-0.9 D. Close agreement (to better than 1%) between the calculated equilibrium and experimentally derived ground-state Rotational constants is achieved. Selected transitions of acenaphthene and fluorene have also been measured in the 3 mm region by conventional free-space absorption spectroscopy, as have transitions of the previously studied azulene (C10H8). The data presented here facilitate deep radio astronomical searches with large radio telescopes.
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Rotational Spectra of the carbon chain negative ions c4h and c8h
The Astrophysical Journal, 2007Co-Authors: C A Gottlieb, M C Mccarthy, H Gupta, Sandra Brunken, Filippo Tamassia, P ThaddeusAbstract:The Rotational Spectra of the butadiyne anion C4H- and the octatetrayne anion C8H- have been detected in the laboratory. Precise spectroscopic constants for these closed-shell molecules have been obtained, which enable their Rotational Spectra to be calculated to high accuracy throughout the radio band. Deep astronomical searches can now be undertaken in essentially any molecular source, including TMC-1 and IRC +10216, where the negative ion C6H- has recently been detected. The large dipole moments and high binding energies of both anions make them good candidates for astronomical detection.
Jurgen Gauss - One of the best experts on this subject based on the ideXlab platform.
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the hyperfine structure in the Rotational Spectra of d217o and hd17o confirmation of the absolute nuclear magnetic shielding scale for oxygen
Journal of Chemical Physics, 2015Co-Authors: Cristina Puzzarini, Gabriele Cazzoli, Michael E Harding, Juana Vazquez, Jurgen GaussAbstract:Guided by theoretical predictions, the hyperfine structures of the Rotational Spectra of mono- and bideuterated-water containing 17O have been experimentally investigated. To reach sub-Doppler resolution, required to resolve the hyperfine structure due to deuterium quadrupole coupling as well as to spin-rotation (SR) and dipolar spin-spin couplings, the Lamb-dip technique has been employed. The experimental investigation and in particular, the Spectral analysis have been supported by high-level quantum-chemical computations employing coupled-cluster techniques and, for the first time, a complete experimental determination of the hyperfine parameters involved was possible. The experimentally determined 17O spin-rotation constants of D217O and HD17O were used to derive the paramagnetic part of the corresponding nuclear magnetic shielding constants. Together with the computed diamagnetic contributions as well as the vibrational and temperature corrections, the latter constants have been employed to confirm t...
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the Rotational Spectra of hd17o and d217o experiment and quantum chemical calculations
Journal of Chemical Physics, 2012Co-Authors: Cristina Puzzarini, Gabriele Cazzoli, Jurgen GaussAbstract:Guided by theoretical predictions, the Rotational spectrum of HD(17)O was recorded and assigned for the first time, while the measurements for D(2)(17)O were extended up to the THz region. For both isotopic species, a large portion of the Rotational spectrum, from 65 GHz (from 200 GHz for the bideuterated isotopologue) up to 1.6 THz, was investigated, thus allowing the accurate determination of the ground-state Rotational and centrifugal-distortion constants. Considering that the Rotational Spectra of water isotopologues are characterized by a very low density of lines and strong centrifugal-distortion effects, the accurate quantum-chemical prediction of the relevant spectroscopic parameters played a crucial role in the line search and assignment as well as in supporting the fitting procedure. In addition to Rotational and centrifugal-distortion constants, the knowledge of the oxygen quadrupole-coupling constants was essential, as the corresponding interaction leads to characteristic features (hyperfine structure) that enabled proper line assignments.
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the Rotational Spectra of hd17o and d217o experiment and quantum chemical calculations
Journal of Chemical Physics, 2012Co-Authors: Cristina Puzzarini, Gabriele Cazzoli, Jurgen GaussAbstract:Guided by theoretical predictions, the Rotational spectrum of HD17O was recorded and assigned for the first time, while the measurements for D217O were extended up to the THz region. For both isotopic species, a large portion of the Rotational spectrum, from 65 GHz (from 200 GHz for the bideuterated isotopologue) up to 1.6 THz, was investigated, thus allowing the accurate determination of the ground-state Rotational and centrifugal-distortion constants. Considering that the Rotational Spectra of water isotopologues are characterized by a very low density of lines and strong centrifugal-distortion effects, the accurate quantum-chemical prediction of the relevant spectroscopic parameters played a crucial role in the line search and assignment as well as in supporting the fitting procedure. In addition to Rotational and centrifugal-distortion constants, the knowledge of the oxygen quadrupole-coupling constants was essential, as the corresponding interaction leads to characteristic features (hyperfine structu...
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Rotational Spectra of rare isotopic species of fluoroiodomethane determination of the equilibrium structure from Rotational spectroscopy and quantum chemical calculations
Journal of Chemical Physics, 2012Co-Authors: Cristina Puzzarini, Gabriele Cazzoli, Jose L Alonso, Juan C Lopez, A Baldacci, Alessandro Baldan, Stella Stopkowicz, Lan Cheng, Jurgen GaussAbstract:Supported by accurate quantum-chemical calculations, the Rotational Spectra of the mono- and bi-deuterated species of fluoroiodomethane, CHDFI and CD2FI, as well as of the 13C-containing species, 13CH2FI, were recorded for the first time. Three different spectrometers were employed, a Fourier-transform microwave spectrometer, a millimeter/submillimter-wave spectrometer, and a THz spectrometer, thus allowing to record a huge portion of the Rotational spectrum, from 5 GHz up to 1.05 THz, and to accurately determine the ground-state Rotational and centrifugal-distortion constants. Sub-Doppler measurements allowed to resolve the hyperfine structure of the Rotational spectrum and to determine the complete iodine quadrupole-coupling tensor as well as the diagonal elements of the iodine spin-rotation tensor. The present investigation of rare isotopic species of CH2FI together with the results previously obtained for the main isotopologue [C. Puzzarini, G. Cazzoli, J. C. Lopez, J. L. Alonso, A. Baldacci, A. Balda...
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Rotational Spectra and equilibrium structures of h2sis and si2s
Journal of Chemical Physics, 2011Co-Authors: Michael C Mccarthy, C A Gottlieb, S Thorwirth, P Thaddeus, Jurgen GaussAbstract:The Rotational Spectra of two small silicon sulfides, silanethione H2SiS and the disilicon sulfide ring Si2S, have been detected in the centimeter band by Fourier transform microwave spectroscopy of a molecular beam; lines of H2SiS were also observed in the millimeter band up to 377 GHz in a glow discharge. Precise Rotational and centrifugal distortionconstants have been determined for the normal and a number of the more abundant rare isotopic species of both closed-shell molecules. Theoretical equilibrium (re) structures of H2SiS and Si2S were derived from coupled-cluster calculations that included triple and quadruple excitations, core correlation, and extrapolation to the basis-set limit. The re structures agree to within 5×10−4 A and 0.1∘with empirical equilibrium (re emp ) structures derived from the experimental Rotational constants, combined with theoretical vibrational and electronic corrections. Both H2SiS and Si2S are good candidates for radioastronomical detection in the circumstellar shells of...
Walther Caminati - One of the best experts on this subject based on the ideXlab platform.
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conformational equilibrium and potential energy functions of the o h internal rotation in the axial and equatorial species of 1 methylcyclohexanol
Journal of Physical Chemistry A, 2016Co-Authors: Lorenzo Spada, Luca Evangelisti, Walther CaminatiAbstract:The Rotational Spectra of four conformers (At, Ag, Et, Eg) of the tertiary alcohol 1-methylcyclohexanol were assigned by pulsed jet Fourier transform microwave spectroscopy. The transitions of two gauche conformers were split in two separated component lines, but it was not possible—from the available measured transitions—to accurately determine their vibrational ΔE0+0- ground-state splittings, respectively. In addition, the Rotational Spectra of the four OD deuterated isotopologues were measured and assigned. For the gauche species of this isotopologue we were able to determine the tunneling splittings, ΔE0+0-(Ag, OD) = 15.581(5) GHz and ΔE0+0-(Eg, OD) = 18.17(3) GHz, respectively. From these splittings the inversion barriers for Ag and Eg were determined, by using a flexible model, to be B2(Ag) = 356(10) and B2(Eg) = 320(10) cm–1, respectively.
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halogen bond and free internal rotation the microwave spectrum of cf3cl dimethyl ether
Journal of Physical Chemistry A, 2014Co-Authors: Luca Evangelisti, Jens-uwe Grabow, Gang Feng, Walther CaminatiAbstract:The Rotational Spectra of two isotopologues of the molecular complex CF3Cl–dimethyl ether have been measured with pulsed jet Fourier transform microwave spectroscopy. The Rotational spectrum encodes information on the global minimum configuration, stabilized by a Cl···O halogen bond, and on the almost free rotation of the −CF3 group.
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free jet Rotational spectrum and tunneling motion of difluoromethane xenon
Journal of Physical Chemistry A, 2006Co-Authors: Walther CaminatiAbstract:The Rotational Spectra of three isotopologues of difluoromethane···xenon have been investigated by free-jet millimeter-wave absorption spectroscopy. Only μc-type transitions have been observed, all...
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the Rotational Spectra of conformers of biomolecules tryptamine
Physical Chemistry Chemical Physics, 2004Co-Authors: Walther CaminatiAbstract:The Rotational Spectra of two conformers of tryptamine have been assigned by free jet millimeter-wave absorption spectroscopy. Both of them are stabilized by an intramolecular N–H⋯π bridge, formed between the amino group of the lateral chain in position 3 and the π system of the pyrrole unity. They correspond to the two most stable conformers found by resonant ion-dip infrared and UV–UV hole burning spectroscopies [J. R. Carney and T. S. Zwier, J. Phys. Chem, 2000, 104, 8677].
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free jet Rotational Spectra in natural abundance of the 13 c and 15 n isotopic species structures and ab initio calculations of equatorial and axial pyrrolidine
Journal of Molecular Structure, 2001Co-Authors: Biagio Velino, Aldo Millemaggi, Adele Dellerba, Walther CaminatiAbstract:Abstract The Rotational Spectra of all singly substituted 13 C and 15 N isotopic species of the equatorial form of pyrrolidine and all singly substituted 13 C isotopic species of the axial form have been measured in natural abundance with millimeter-wave free jet technique and r s and r 0 heavy atom geometries have been determined. Various sets of ab initio calculations give contrasting results for the energy difference between the two conformers.
Cristina Puzzarini - One of the best experts on this subject based on the ideXlab platform.
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vms rot a new module of the virtual multifrequency spectrometer for simulation interpretation and fitting of Rotational Spectra
Journal of Chemical Theory and Computation, 2017Co-Authors: Daniele Licari, Cristina Puzzarini, Nicola Tasinato, Lorenzo Spada, Vincenzo BaroneAbstract:The Virtual Multifrequency Spectrometer (VMS) is a tool that aims at integrating a wide range of computational and experimental spectroscopic techniques with the final goal of disclosing the static and dynamic physical–chemical properties “hidden” in molecular Spectra. VMS is composed of two parts, namely, VMS-Comp, which provides access to the latest developments in the field of computational spectroscopy, and VMS-Draw, which provides a powerful graphical user interface (GUI) for an intuitive interpretation of theoretical outcomes and a direct comparison to experiment. In the present work, we introduce VMS-ROT, a new module of VMS that has been specifically designed to deal with Rotational spectroscopy. This module offers an integrated environment for the analysis of Rotational Spectra: from the assignment of Spectral transitions to the refinement of spectroscopic parameters and the simulation of the spectrum. While bridging theoretical and experimental Rotational spectroscopy, VMS-ROT is strongly integr...
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the hyperfine structure in the Rotational Spectra of d217o and hd17o confirmation of the absolute nuclear magnetic shielding scale for oxygen
Journal of Chemical Physics, 2015Co-Authors: Cristina Puzzarini, Gabriele Cazzoli, Michael E Harding, Juana Vazquez, Jurgen GaussAbstract:Guided by theoretical predictions, the hyperfine structures of the Rotational Spectra of mono- and bideuterated-water containing 17O have been experimentally investigated. To reach sub-Doppler resolution, required to resolve the hyperfine structure due to deuterium quadrupole coupling as well as to spin-rotation (SR) and dipolar spin-spin couplings, the Lamb-dip technique has been employed. The experimental investigation and in particular, the Spectral analysis have been supported by high-level quantum-chemical computations employing coupled-cluster techniques and, for the first time, a complete experimental determination of the hyperfine parameters involved was possible. The experimentally determined 17O spin-rotation constants of D217O and HD17O were used to derive the paramagnetic part of the corresponding nuclear magnetic shielding constants. Together with the computed diamagnetic contributions as well as the vibrational and temperature corrections, the latter constants have been employed to confirm t...
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the Rotational Spectra of hd17o and d217o experiment and quantum chemical calculations
Journal of Chemical Physics, 2012Co-Authors: Cristina Puzzarini, Gabriele Cazzoli, Jurgen GaussAbstract:Guided by theoretical predictions, the Rotational spectrum of HD(17)O was recorded and assigned for the first time, while the measurements for D(2)(17)O were extended up to the THz region. For both isotopic species, a large portion of the Rotational spectrum, from 65 GHz (from 200 GHz for the bideuterated isotopologue) up to 1.6 THz, was investigated, thus allowing the accurate determination of the ground-state Rotational and centrifugal-distortion constants. Considering that the Rotational Spectra of water isotopologues are characterized by a very low density of lines and strong centrifugal-distortion effects, the accurate quantum-chemical prediction of the relevant spectroscopic parameters played a crucial role in the line search and assignment as well as in supporting the fitting procedure. In addition to Rotational and centrifugal-distortion constants, the knowledge of the oxygen quadrupole-coupling constants was essential, as the corresponding interaction leads to characteristic features (hyperfine structure) that enabled proper line assignments.
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the Rotational Spectra of hd17o and d217o experiment and quantum chemical calculations
Journal of Chemical Physics, 2012Co-Authors: Cristina Puzzarini, Gabriele Cazzoli, Jurgen GaussAbstract:Guided by theoretical predictions, the Rotational spectrum of HD17O was recorded and assigned for the first time, while the measurements for D217O were extended up to the THz region. For both isotopic species, a large portion of the Rotational spectrum, from 65 GHz (from 200 GHz for the bideuterated isotopologue) up to 1.6 THz, was investigated, thus allowing the accurate determination of the ground-state Rotational and centrifugal-distortion constants. Considering that the Rotational Spectra of water isotopologues are characterized by a very low density of lines and strong centrifugal-distortion effects, the accurate quantum-chemical prediction of the relevant spectroscopic parameters played a crucial role in the line search and assignment as well as in supporting the fitting procedure. In addition to Rotational and centrifugal-distortion constants, the knowledge of the oxygen quadrupole-coupling constants was essential, as the corresponding interaction leads to characteristic features (hyperfine structu...
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Rotational Spectra of rare isotopic species of fluoroiodomethane determination of the equilibrium structure from Rotational spectroscopy and quantum chemical calculations
Journal of Chemical Physics, 2012Co-Authors: Cristina Puzzarini, Gabriele Cazzoli, Jose L Alonso, Juan C Lopez, A Baldacci, Alessandro Baldan, Stella Stopkowicz, Lan Cheng, Jurgen GaussAbstract:Supported by accurate quantum-chemical calculations, the Rotational Spectra of the mono- and bi-deuterated species of fluoroiodomethane, CHDFI and CD2FI, as well as of the 13C-containing species, 13CH2FI, were recorded for the first time. Three different spectrometers were employed, a Fourier-transform microwave spectrometer, a millimeter/submillimter-wave spectrometer, and a THz spectrometer, thus allowing to record a huge portion of the Rotational spectrum, from 5 GHz up to 1.05 THz, and to accurately determine the ground-state Rotational and centrifugal-distortion constants. Sub-Doppler measurements allowed to resolve the hyperfine structure of the Rotational spectrum and to determine the complete iodine quadrupole-coupling tensor as well as the diagonal elements of the iodine spin-rotation tensor. The present investigation of rare isotopic species of CH2FI together with the results previously obtained for the main isotopologue [C. Puzzarini, G. Cazzoli, J. C. Lopez, J. L. Alonso, A. Baldacci, A. Balda...
C A Gottlieb - One of the best experts on this subject based on the ideXlab platform.
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pure Rotational Spectra of tio and tio2 in vy canis majoris
Astronomy and Astrophysics, 2013Co-Authors: T Kaminski, C A Gottlieb, M C Mccarthy, Sandra Brunken, H S P Muller, K Young, N A Patel, K M Menten, J M Winters, Leen DecinAbstract:We report the first detection of pure Rotational transitions of TiO and TiO2 at (sub-)millimeter wavelengths towards the red supergiant VY CMa. A Rotational temperature, Trot, of about 250 K was derived for TiO2. Although Trot was not well constrained for TiO, it is likely somewhat higher than that of TiO2. The detection of the Ti oxides confirms that they are formed in the circumstellar envelopes of cool oxygen-rich stars and may be the “seeds” of inorganic-dust formation, but alternative explanations for our observation of TiO and TiO2 in the cooler regions of the envelope cannot be ruled out at this time. The observations suggest that a significant fraction of the oxides is not converted to dust, but instead remains in the gas phase throughout the outflow.
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the Rotational Spectra of 29 sic 2 and 30 sic 2
Astrophysical Journal Supplement Series, 2011Co-Authors: C A Gottlieb, P Thaddeus, Sandra Brunken, Damian L Kokkin, K Young, N A Patel, Michael C MccarthyAbstract:The Rotational Spectra of {sup 29}SiC{sub 2} and {sup 30}SiC{sub 2}, two silicon isotopic species of the abundant astronomical ring {sup 28}SiC{sub 2}, have been characterized in the millimeter band between 140 and 360 GHz in a low pressure discharge through SiH{sub 4}, C{sub 2}H{sub 2}, and Ar. Precise Rotational and centrifugal distortion constants have been derived for both species by fitting a standard asymmetric top Hamiltonian to 38 a-type transitions of {sup 29}SiC{sub 2} and 35 of {sup 30}SiC{sub 2}; the data sets include transitions up to K{sub a} = 8 and at least J = 16. With these new measurements in hand, the most intense radio transitions of both species either have been measured or can now be predicted to better than 1 km s{sup -1} in equivalent radial velocity up to 500 GHz, more than adequate accuracy for Spectral line identifications in circumstellar shells of evolved carbon stars such as IRC+10216 where SiC{sub 2} is conspicuous. More than 10 new lines of {sup 29}SiC{sub 2} and {sup 30}SiC{sub 2} have been identified between 295 and 354 GHz in the interferometric Spectral line survey of IRC+10216 with the Submillimeter Array.
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Rotational Spectra and equilibrium structures of h2sis and si2s
Journal of Chemical Physics, 2011Co-Authors: Michael C Mccarthy, C A Gottlieb, S Thorwirth, P Thaddeus, Jurgen GaussAbstract:The Rotational Spectra of two small silicon sulfides, silanethione H2SiS and the disilicon sulfide ring Si2S, have been detected in the centimeter band by Fourier transform microwave spectroscopy of a molecular beam; lines of H2SiS were also observed in the millimeter band up to 377 GHz in a glow discharge. Precise Rotational and centrifugal distortionconstants have been determined for the normal and a number of the more abundant rare isotopic species of both closed-shell molecules. Theoretical equilibrium (re) structures of H2SiS and Si2S were derived from coupled-cluster calculations that included triple and quadruple excitations, core correlation, and extrapolation to the basis-set limit. The re structures agree to within 5×10−4 A and 0.1∘with empirical equilibrium (re emp ) structures derived from the experimental Rotational constants, combined with theoretical vibrational and electronic corrections. Both H2SiS and Si2S are good candidates for radioastronomical detection in the circumstellar shells of...
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Rotational Spectra of vibrationally excited cch and ccd
Journal of Chemical Physics, 2007Co-Authors: T C Killian, C A Gottlieb, P ThaddeusAbstract:The millimeter-wave Rotational Spectra of the lowest bending and stretching vibrational levels of CCH and CCD were observed in a low pressure discharge through acetylene and helium. The Rotational, centrifugal distortion, and fine structure constants were determined for the (0200) and (0220) bending states, the (100) and (001) stretching levels, and the (011) combination level of CCH. The same pure bending and stretching levels, and the (110) combination level were observed in CCD. Apparent anomalies in the spectroscopic constants in the bending states were shown to be due to l-type resonances. Hyperfine constants, which in CCH are sensitive to the degree of admixture of the AΠ2 excited electronic state, were determined in the excited vibrational levels of both isotopic species. Theoretical Fermi contact and dipole-dipole hyperfine constants calculated by Peric et al. [J. Mol. Spectrosc. 150, 70 (1991)] were found to be in excellent agreement with the measured constants. In CCD, new Rotational lines tenta...
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Rotational Spectra of small pahs acenaphthene acenaphthylene azulene and fluorene
The Astrophysical Journal, 2007Co-Authors: S Thorwirth, P Theule, C A Gottlieb, M C Mccarthy, P ThaddeusAbstract:Pure Rotational Spectra of four small polycyclic aromatic hydrocarbons have been observed by Fourier transform microwave spectroscopy of a molecular beam in the frequency range from 7 to 37 GHz. Initial searches for acenaphthene (C12H10), acenaphthylene (C12H8), and fluorene (C13H10) were guided by quantum chemical calculations performed at the B3LYP/cc-pVTZ level of theory. All three molecules exhibit b-type Rotational Spectra and are calculated to be moderately polar, with dipole moments of 0.3-0.9 D. Close agreement (to better than 1%) between the calculated equilibrium and experimentally derived ground-state Rotational constants is achieved. Selected transitions of acenaphthene and fluorene have also been measured in the 3 mm region by conventional free-space absorption spectroscopy, as have transitions of the previously studied azulene (C10H8). The data presented here facilitate deep radio astronomical searches with large radio telescopes.