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Walther Caminati - One of the best experts on this subject based on the ideXlab platform.
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Rotational Spectrum tunneling motions and intramolecular potential barriers in benzyl mercaptan
Journal of Physical Chemistry A, 2019Co-Authors: Rizalina Tama Saragi, Marcos Juanes, L Enriquez, Walther Caminati, Alberto Lesarri, Martín JaraízAbstract:: The Rotational Spectrum of benzyl mercaptan (parent and four isotopologues) has been assigned in a supersonic jet expansion using chirped-pulse Fourier transform microwave spectroscopy. The Spectrum is characterized by torsional tunneling doublings, strongly perturbed by Coriolis interactions. The experimental Rotational constants reveal that the sulfur atom is located above the ring plane in a gauche conformation. The torsion dihedral θ0 = φ (SCα-C1C2) is approximately 74°, according to a flexible molecular model calculation reproducing the energy separation (ΔE01 ∼ 2180.4 MHz) between the first two torsional substates. The global minimum configuration is 4-fold degenerate, corresponding to potential minima with θ0 ≈ ±74° and ±(180-74)°. The four equivalent minima are separated by potential barriers at θ = ±90°, 0°, or 180°. The tunneling splittings are caused by the potential barrier at θ = ± 90°, while the barriers at torsions of 0° or 180° are too large to generate detectable splittings. The tunnelling barrier has been determined as 248 cm-1, similar to the value obtained with high-level MP2 ab initio calculations (259 cm-1), but smaller than in benzyl alcohol (280 cm-1).
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Modeling the internal rotation tunnelling in benzyl alcohol by ring fluorination: The Rotational Spectrum of 3,5-difluorobenzyl alcohol
Elsevier, 2019Co-Authors: Luca Evangelisti, Walther CaminatiAbstract:The Rotational spectra of the OH and OD isotopologues of 3,5-difluorobenzyl alcohol have been measured by pulsed jet Fourier transform microwave spectroscopy. The main structural evidence is that the OCα-C1C2 dihedral angle, approximately 20°, is ca. 40° smaller than in benzyl alcohol. This difference is reflected in the features of the Rotational Spectrum: μc-type (instead of μb-) transitions are split into two evenly spaced component lines (by 14.367(1) × 2 MHz) showing that the CH2OH group undergoes a tunnelling motion which connects two equivalent minima above and below the aromatic ring. The barrier for the interconversion of the two mirror form has been estimated from the experimental tunnelling splitting to be 380 cm−1. Keywords: Transient chirality, Rotational spectroscopy, Large amplitude motions, Supersonic expansions, Inversion tunnellin
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Rotational Spectrum of the tetrafluoromethane ethylene oxide
Journal of Molecular Spectroscopy, 2017Co-Authors: Qian Gou, Luca Evangelisti, Gang Feng, Walther CaminatiAbstract:Abstract The Rotational Spectrum of one conformer of the CF 4 –ethylene oxide complex has been measured by using a pulsed jet Fourier-transform microwave spectrometer. The observed conformer is stabilized by a CF 3 ⋯O halogen bond, with a distance r C⋯O of ∼3.341 A . No experimental evidence of the internal rotation of CF 4 with respect to ethylene oxide has been observed, but it is expected to be almost free ( V 3 ∼ 14 cm −1 from ab initio calculations).
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probing the lone pair π hole interaction in perfluorinated heteroaromatic rings the Rotational Spectrum of pentafluoropyridine water
Journal of Physical Chemistry Letters, 2016Co-Authors: Camilla Calabrese, Walther Caminati, Qian Gou, Assimo Maris, Sonia MelandriAbstract:The Rotational Spectrum of the weakly bound complex pentafluoropyridine·water has been investigated with pulsed jet Fourier transform microwave spectroscopy. From the analysis of the Rotational parameters of the parent species and of three water isotopologues, the structural arrangement of the adduct has been unambiguously established. The results show that the full ring fluorination of pyridine has a dramatic effect on its binding properties: It inverts the electron density distribution above the ring, creating a π-hole, with respect to the typical π-cloud of benzene and pyridine. In the complex the water moiety lies above the aromatic ring with the oxygen lone pairs pointing toward its center. This lone pair···π-hole interaction stabilizes the adduct, and it is more stable than the in-plane O–H···N hydrogen bond normally found in the complexes involving nitrogen heterocyclic aromatic rings. Evidence of a large amplitude motion involving the weakly bound water molecule has also been observed and discussed.
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the Rotational Spectrum of formic acid fluoroacetic acid
Journal of Molecular Spectroscopy, 2014Co-Authors: Luca Evangelisti, Gang Feng, Qian Gou, Walther CaminatiAbstract:Abstract The pure Rotational Spectrum of formic acid–fluoroacetic acid complex was measured in the range 6–18 GHz using a cavity-based pulsed jet Fourier transform microwave spectrometer. In all, 73 transitions were measured for four isotopologues of the complex where the fluoroacetic acid is in trans form. The conformational stabilities, structures and spectroscopic parameters were determined with ab initio calculations at MP2 levels of theory with 6-311++G(d,p) basis set. The deuterations of the carboxylic groups generate an increase of the distance between the two subunits of the complex. This phenomenon (Ubbelohde effect) has been quantified using the changes of the P aa planar moment of inertia upon OH → OD substitutions.
Brooks H Pate - One of the best experts on this subject based on the ideXlab platform.
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the pure Rotational Spectrum of glycolaldehyde isotopologues observed in natural abundance
Journal of Molecular Spectroscopy, 2013Co-Authors: Brandon P Carroll, Brooks H Pate, Brett A Mcguire, Daniel P Zaleski, Justin L Neill, Susanna Widicus L WeaverAbstract:Abstract The pure Rotational Spectrum of glycolaldehyde has been recorded from 6.5–20 GHz and 25–40 GHz in two pulsed-jet chirped pulse Fourier transform microwave spectrometers. The high phase stability of the spectrometers enables deep signal integration, allowing transitions from the 13 C-substituted, 18 O-substituted, and deuterium-substituted isotopologues to be observed in natural abundance. Transitions from HCOCH 2 18 OH are reported for the first time. Additional transitions from the 13 C-substituted, deuterium-substituted, and HC 18 OCH 2 OH isotopologues, as well as previously unobserved weak lines from the main isotopologue, have been observed. Transitions from all isotopologues are used with previously reported transitions to refine the spectroscopic parameters for each isotopologue. A Kraitchman analysis was performed using the experimental Rotational constants to determine the molecular structure of glycolaldehyde.
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measuring picosecond isomerization kinetics via broadband microwave spectroscopy
Science, 2008Co-Authors: Brian C Dian, Gordon G Brown, Kevin O Douglass, Brooks H PateAbstract:The Rotational Spectrum of a highly excited molecule is qualitatively different from its pure Rotational Spectrum and contains information about the intramolecular dynamics. We have developed a broadband Fourier transform microwave spectrometer that uses chirped-pulse excitation to measure a Rotational Spectrum in the 7.5- to 18.5-gigahertz range in a single shot and thereby reduces acquisition time sufficiently to couple molecular Rotational spectroscopy with tunable laser excitation. After vibrationally exciting a single molecular conformation of cyclopropane carboxaldehyde above the barrier to C–C single-bond isomerization, we applied line-shape analysis of the dynamic Rotational Spectrum to reveal a product yield and picosecond reaction rate that were significantly different from statistical predictions. The technique should be widely applicable to dynamical studies of radical intermediates, molecular complexes, and conformationally flexible molecules with biological interest.
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the Rotational Spectrum of epifluorohydrin measured by chirped pulse fourier transform microwave spectroscopy
Journal of Molecular Spectroscopy, 2006Co-Authors: Gordon G Brown, Brian C Dian, Kevin O Douglass, Scott M Geyer, Brooks H PateAbstract:Abstract The Rotational Spectrum of epifluorohydrin measured by chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy is presented. A new CP-FTMW spectrometer capable of measuring the entire 7.5–18.5 GHz Spectrum with a single polarizing pulse is described briefly. The CP-FTMW spectrometer takes advantage of recent advances in digital electronics by utilizing a 4.2 GS/s arbitrary waveform generator as a frequency source and a 12 GHz digital oscilloscope to digitize the down converted molecular free induction decay (FID). Signal averaging in the time domain is used to increase the signal-to-noise ratio. The Rotational constants of three unique conformers of epifluorohydrin were measured, as well as the Rotational constants of the three unique 13 C isotopomers and the 18 O isotopomer (in natural abundance) of the most stable conformer. The Rotational constants of the two less stable conformers differ significantly from those previously reported [F.G. Fujiwara, J.L. Painter, H. Kim, J. Mol. Struct. 41 (1977) 169–175]. Ab initio calculations were performed for all three conformations and are compared to experimental values.
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Rotational spectroscopy of the first excited state of the acetylenic c h stretch of 3 fluoropropyne performed by infrared fourier transform microwave microwave triple resonance spectroscopy
Journal of Molecular Spectroscopy, 2005Co-Authors: Kevin O Douglass, Brooks H Pate, R D Suenram, Frances S Rees, Igor I LeonovAbstract:Abstract The Rotational spectra of 3-fluoropropyne in the ground and first excited acetylenic C–H stretch vibrational state have been measured. The pure Rotational Spectrum of the normal species and the 13C isotopomers were measured using FTMW-cwMW double-resonance spectroscopy based on the Autler–Townes (AC Stark) effect. The lineshape properties of this measurement make it possible to determine the transition strength, ΔJ-selection rules, and the relative energy ordering of the quantum states. The frequency accuracy of this technique is tested against a previous pure Rotational study of 3-fluoropropyne. The Rotational Spectrum of vibrationally excited state was obtained through IR-FTMW-cwMW methods. In this technique a single-longitudinal-mode pulsed infrared laser source vibrationally excites the acetylenic C–H stretch with J-selectivity. The Rotational Spectrum of the excited state is then obtained by FTMW and FTMW-cwMW double-resonance methods. The excited-state measurements have a signal-to-noise ratio comparable to the pure Rotational Spectrum. The residuals in the excited-state fit are larger than those obtained in the ground-state fit. This greater deviation from a standard asymmetric top Spectrum is most likely due to weak perturbations to the acetylenic C–H Spectrum.
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the Rotational Spectrum of a highly vibrationally mixed quantum state ii the eigenstate resolved spectroscopy analog to dynamic nuclear magnetic resonance spectroscopy
Journal of Chemical Physics, 1999Co-Authors: Brooks H PateAbstract:The description of the Rotational Spectrum of a single molecular eigenstate in an energy region where conformational isomerization can occur is presented. The conformational isomerization rate can be determined from an analysis of the overall line shape of the Spectrum. The isomerization dynamics are investigated through a time-domain analysis. It is shown that the nonstationary state produced by coherent microwave excitation has a well-defined conformational structure. However, the individual molecular eigenstates are a mixture of rovibrational states associated with the two conformations. The structural localization decays to the eigenstate equilibrium value at a rate defined as the isomerization rate. It is also shown that the line shape of the Spectrum coalesces as the isomerization rate exceeds the difference between the characteristic Rotational frequencies of the two conformers. The line shape profile of the eigenstate-resolved Spectrum is well described by the Bloch equations modified for chemical...
A C Legon - One of the best experts on this subject based on the ideXlab platform.
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the ground state Rotational Spectrum and molecular geometry of ethynylstannane
Physical Chemistry Chemical Physics, 2006Co-Authors: Jeanclaude Guillemin, Stephanie Legoupy, Susan G Batten, A C LegonAbstract:The ground-state Rotational spectra of 24 isotopomers of ethynylstannane have been observed by pulsed-jet, Fourier-transform microwave spectroscopy. The spectroscopic constants, B0,DJ and DJK are reported for symmetric-top isotopomers H3nSn12C12CH, where n = 116, 117, 118, 119, 120, 122 and 124, D3nSn12C12CH, where n = 116, 118, 120, 122 and 124, H3nSn13C12 CH and H3nSn12C13CH , where n = 116,118 and 120, and H3nSn12C12CD, where n = 116, 118 and 120. In addition, the values of A0, B0, C0, ΔJ and ΔJK were obtained for the three asymmetric-top isotopomers DH2nSn12C12CH, where n = 116, 118 and 120. Hyperfine structure was resolved and assigned in the transitions of the isotopomers H3nSnCCD, where n = 116, 118 and 120, and in the isotopomers H3117SnCCH and H3119SnCCH. In the former group, the hyperfine structure arises from D nuclear quadrupole coupling while in the latter group its origin lies in the spin-rotation coupling of the I = 1/2 Sn nuclear spin to the Rotational motion. For these isotopomers, D nuclear quadrupole and spin-rotation coupling constants are determined where appropriate. The Rotational constants obtained for the 24 isotopomers of H3SnCCH were used to obtain the following types of molecular geometry for ethynylstannane: r0, rs, and rm.
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Rotational Spectrum of the trimethylphosphine hydrogen fluoride complex
Chemical Physics Letters, 1998Co-Authors: S A Cooke, A C LegonAbstract:Abstract The Rotational spectra of the four isotopomers (CH 3 ) 3 P⋯HF, (CH 3 ) 3 P⋯DF, (CH 3 ) 2 ( 13 CH 3 )P⋯HF and (CD 3 ) 3 P⋯HF of a hydrogen-bonded complex formed by trimethylphosphine and hydrogen fluoride have been observed by pulsed-nozzle Fourier-transform microwave spectroscopy. The H, F nuclear spin–spin coupling constant D HF aa and the D-nuclear quadrupole coupling constant χ D aa were determined for the first two isotopomers. Interpretation of these coupling constants in conjunction with Rotational constants and centrifugal distortion constants allows the conclusion that the intermolecular binding is relatively weak ( k σ =17.2(3) N m −1 ), with only a small lengthening δ r ≈0.012 A of the HF bond on formation of a symmetric-top complex (CH 3 ) 3 P⋯HF having r (P⋯F)=3.120(2) A.
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nature and angular geometry of the pre reactive complex thiirane chlorine monofluoride from its Rotational Spectrum
Chemical Physics Letters, 1996Co-Authors: C M Evans, John H Holloway, A C LegonAbstract:Abstract The Rotational Spectrum of the pre-reactive complex thiirane-ClF was detected with a fast-mixing nozzle in an FT microwave spectrometer. Rotational constants, centrifugal distortion constants, Cl-nuclear quadrupole and spin-rotation coupling constants were determined for the isotopomers (CH 2 ) 2 S… 35 ClF and (CH 2 ) 2 S… 37 ClF. The complex has C s symmetry, with a nearly collinear arrangement of the S…ClF nuclei ( σ ≈3.5°) and the ClF axis making an angle φ =95° with the C 2 axis of thiirane. The Cl-nuclear quadrupole coupling constant χ zz along the ClF internuclear axis suggests a significant contribution of the ionic structure [(CH 2 ) 2 SCl] + …F − to a valence-bond description of the complex.
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the Rotational Spectrum of the argon thiirane van der waals molecule
Chemical Physics Letters, 1992Co-Authors: A C Legon, David G. ListerAbstract:Abstract The Rotational Spectrum of the argon—thiirane van der Waals molecule has been observed using pulsed-nozzle, Fourier-transform microwave spectroscopy. Transitions due to μa and μb components of the electric dipole moment have been observed and used to derive Rotational and quartic centrifugal distortion constants. The molecule has Cs symmetry with a distance R = 3.79 pm from the centre of mass of thiirane to the argon atom and an angle θ = 98° between this vector and the bisector of the CSC bond angle of the thiirane molecule. An upper limit of 10 kHz is placed on the ground vibrational state inversion frequency in Ar…S(CH2)2.
Zbigniew Kisiel - One of the best experts on this subject based on the ideXlab platform.
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high j Rotational Spectrum of toluene in m 3 torsional states
Journal of Molecular Spectroscopy, 2017Co-Authors: Vadim V Ilyushin, Zbigniew Kisiel, E A Alekseev, L PszczolkowskiAbstract:Abstract The study of the Rotational Spectrum of toluene (C 6 H 5 CH 3 ) is considerably extended to include transitions in | m | ⩽ 3 torsional states up to the onset of the submillimeter wave region. New data involving torsion–rotation transitions up to 336 GHz were combined with previously published measurements and fitted using the rho-axis-method torsion–rotation Hamiltonian. The final fit used 50 parameters to give an overall weighted root-mean-square deviation of 0.69 for a dataset consisting of 8924 transitions with J up to 94 and K a up to 50. The new analysis allowed us to resolve all problems encountered previously for m = 0 transitions beyond a certain combination of quantum numbers J and K a when many lines of appreciable intensity and unambiguous assignment deviated from the distorted asymmetric rotor treatment. Those discrepancies are now identified to result from m = 0 ↔ m = 3 and m = 0 ↔ m = −3 resonances, which have been successfully encompassed by the current fit. At the same time an analogous problem was discovered and fitted for m = 2 transitions, which were found to be affected by many m = 1 ↔ m = 2 resonances.
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broadband Rotational spectroscopy of acrylonitrile vibrational energies from perturbations
Journal of Molecular Spectroscopy, 2012Co-Authors: Zbigniew Kisiel, L Pszczolkowski, Ivan R. Medvedev, Brian J Drouin, Carolyn S Brauer, John C Pearson, Sarah M Fortman, Christopher F NeeseAbstract:Abstract The coverage of the room-temperature Rotational Spectrum of acrylonitrile has been expanded to a total of 1170 GHz, by recording broadband spectral segments at frequencies ranging 90–1900 GHz. This corresponds, in total, to 61.6% coverage of the Rotational Spectrum up to 1.9 THz and facilitated an in depth study of Rotational transitions in the lowest vibrational states of acrylonitrile and up to large values of Rotational quantum numbers. Multiple perturbations between the four lowest vibrational states of the molecule have been identified and successfully fitted within the framework of a coupled four state Hamiltonian. The fit encompasses over 12 500 measured transition frequencies, and delivers precise wavenumbers for the three lowest excited vibrational states entirely on the basis of perturbations in the Rotational Spectrum: ν11 = 228.29986(2), ν15 = 332.67811(2), and 2ν11 = 457.17496(2) cm−1. The new results are compared with ab initio anharmonic force field calculations and the techniques used to deal in an efficient manner with a broadband, high-resolution Spectrum of this type are also described in some detail.
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Rotational Spectrum of trans trans diethyl ether in the ground and three excited vibrational states
Journal of Molecular Spectroscopy, 2005Co-Authors: Zbigniew Kisiel, L Pszczolkowski, Manfred Winnewisser, Frank C. De Lucia, Ivan R. Medvedev, Eric HerbstAbstract:Abstract We report the results of a comprehensive reinvestigation of the Rotational Spectrum of diethyl ether based on broadband millimetre-wave spectra recently recorded at The Ohio State University and in Warsaw, covering the frequency region 108–366 GHz. The data set for the ground vibrational state of trans – trans diethyl ether has been extended to over 2000 lines and improved spectroscopic constants have been determined. Rotational spectra in the first excited vibrational states of the three lowest vibrational modes of trans – trans -diethyl ether, ν 20 , ν 39 , and ν 12 have been assigned. The v 20 = 1 and v 39 = 1 states are near 100 cm −1 in vibrational term value and are coupled by a strong c -axis Coriolis interaction, which gives rise to many spectacular manifestations in the Rotational Spectrum. All of these effects have been successfully fitted for a dataset comprising over 3000 transitions, leading to precise determination of the energy difference between these states, (Δ E / hc )=10.400222(5) cm −1 . A newly developed software package for assignment and analysis of broadband spectra is described and made available.
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The millimeter-wave Rotational Spectrum of fluorobenzene
Journal of Molecular Spectroscopy, 2005Co-Authors: Zbigniew Kisiel, E. Białkowska-jaworska, Lech PszczółkowskiAbstract:Abstract The room-temperature Rotational Spectrum of fluorobenzene was studied in the frequency region 167–318 GHz. Rotational transitions were assigned and measured in the ground vibrational state, and all six excited vibrational states with energies below 600 cm−1, i.e., v11 = 1, v11 = 2, v18b = 1, v16a = 1, v16b = 1, and v6a = 1. Accurate quartic-level spectroscopic constants were determined for all states, allowing spectral predictions well into the submillimeter region. The states v18b = 1 and v16a = 1 were found to be connected by a strong Coriolis interaction, which allowed precise determination of their energy separation, ΔE = 7.455088(3) cm−1. Unambiguous assignment of vibrational modes was made on the basis of the calculated inertial defect and nuclear spin statistical weights. Rotational constants for the 13C4 isotopomer have also been redetermined and two new least-squares determinations of the geometry of fluorobenzene, r0 and r m ( 1 L ) are reported.
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investigation of the Rotational Spectrum of pyrimidine from 3 to 337 ghz molecular structure nuclear quadrupole coupling and vibrational satellites
Journal of Molecular Spectroscopy, 1999Co-Authors: Zbigniew Kisiel, L Pszczolkowski, Juan C Lopez, Jose L Alonso, Assimo Maris, Walther CaminatiAbstract:Abstract A comprehensive reinvestigation of the Rotational Spectrum of pyrimidine was carried out by using several different spectrometers. All singly substituted 13 C- and 15 N-isotopic species of pyrimidine have been measured in natural abundance with millimeter-wave free jet and waveguide Fourier transform microwave techniques, and complete r s and r 0 heavy atom geometries have been determined. The ground state Rotational Spectrum in the centimeter-wave region was measured at sub-Doppler resolution of the cavity Fourier transform spectrometer and all elements in the inertial and principal nuclear quadrupole-coupling tensors of the nitrogen nuclei in pyrimidine have been determined. The room-temperature Spectrum was measured up to 337 GHz and J = 66 with BWO-based spectrometers and sextic level centrifugal distortion constants in the Rotational Hamiltonian have been determined for the ground state and three lowest vibrational fundamentals of pyrimidine.
L M Ziurys - One of the best experts on this subject based on the ideXlab platform.
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the pure Rotational Spectrum of hps x1a chemical bonding in second row elements
Journal of Chemical Physics, 2011Co-Authors: D T Halfen, D J Clouthier, L M Ziurys, Valerio Lattanzi, M C Mccarthy, P Thaddeus, S ThorwirthAbstract:The pure Rotational Spectrum of HPS, as well as its 34S and D isotopologues, has been recorded at microwave, millimeter, and submillimeter wavelengths, the first observation of this molecule in the gas phase. The data were obtained using a combination of millimeter direct absorption, Fourier transform microwave (FTMW), and microwave–microwave double-resonance techniques, which cover the total frequency range from 15 to 419 GHz. Quantum chemical calculations at the B3LYP and CCSD(T) levels were also performed to aid in spectral identification. HPS was created in the direct absorption experiment from a mixture of elemental phosphorus, H2S, and Ar carrier gas; DPS was produced by adding D2. In the FTMW study, these species were generated in a pulsed discharge nozzle from PH3 and H2S or D2S, diluted in neon. The spectra recorded for HPS and its isotopologues exhibit clear asymmetric top patterns indicating bent structures; phosphorus hyperfine splittings were also observed in HPS, but not DPS. Analysis of the...
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the Rotational Spectrum of cucch x σ1 a fourier transform microwave discharge assisted laser ablation spectroscopy and millimeter submillimeter study
Journal of Chemical Physics, 2010Co-Authors: D T Halfen, D J Clouthier, B T Harris, L M ZiurysAbstract:The pure Rotational Spectrum of CuCCH in its ground electronic state (X Σ1+) has been measured in the frequency range of 7–305 GHz using Fourier transform microwave (FTMW) and direct absorption millimeter/submillimeter methods. This work is the first spectroscopic study of CuCCH, a model system for copper acetylides. The molecule was synthesized using a new technique, discharge assisted laser ablation spectroscopy (DALAS). Four to five Rotational transitions were measured for this species in six isotopologues (C63uCCH, C65uCCH, C63uC13CH, C63uCC13H, C63uC13C13H, and C63uCCD); hyperfine interactions arising from the copper nucleus were resolved, as well as smaller splittings in CuCCD due to deuterium quadrupole coupling. Five Rotational transitions were also recorded in the millimeter region for C63uCCH and C65uCCH, using a Broida oven source. The combined FTMW and millimeter spectra were analyzed with an effective Hamiltonian, and Rotational, electric quadrupole (Cu and D) and copper nuclear spin-rotatio...
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the pure Rotational Spectrum of zno in the x1σ and a3πi states
Journal of Molecular Spectroscopy, 2009Co-Authors: Lindsay N Zack, R L Pulliam, L M ZiurysAbstract:Abstract The pure Rotational Spectrum of ZnO has been measured in its ground X 1 Σ + and excited a 3 Π i states using direct-absorption methods in the frequency range 239–514 GHz. This molecule was synthesized by reacting zinc vapor, generated in a Broida-type oven, with N 2 O under DC discharge conditions. In the X 1 Σ + state, five to eight Rotational transitions were recorded for each of the five isotopologues of this species ( 64 ZnO, 66 ZnO, 67 ZnO, 68 ZnO, and 70 ZnO) in the ground and several vibrational states ( v = 1–4). Transitions for three isotopologues ( 64 ZnO, 66 ZnO, and 68 ZnO) were measured in the a 3 Π i state for the v = 0 level, as well as from the v = 1 state of the main isotopologue. All three spin–orbit components were observed in the a 3 Π i state, each exhibiting splittings due to lambda-doubling. Rotational constants were determined for the X 1 Σ + state of zinc oxide. The a 3 Π i state data were fit with a Hund’s case (a) Hamiltonian, and Rotational, spin–orbit, spin–spin, and lambda-doubling constants were established. Equilibrium parameters were also determined for both states. The equilibrium bond length determined for ZnO in the X 1 Σ + state is 1.7047 A, and it increases to 1.8436 A for the a excited state, consistent with a change from a π 4 to a π 3 σ 1 configuration. The estimated vibrational constants of ω e ∼ 738 and 562 cm −1 for the ground and a state agreed well with prior theoretical and experimental investigations; however, the estimated dissociation energy of 2.02 eV for the a 3 Π i state is significantly higher than previous predictions. The lambda-doubling constants suggest a low-lying 3 Σ state.
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fine structure and hyperfine perturbations in the pure Rotational Spectrum of the vcl radical in its x δ5r state
Journal of Chemical Physics, 2009Co-Authors: D T Halfen, L M Ziurys, John M BrownAbstract:The pure Rotational Spectrum of the VCl radical in its Δ5r ground state has been recorded in the range 236–417 GHz using millimeter/submillimeter direct absorption techniques. This species was created in an ac discharge of VCl4 and argon. Ten Rotational transitions of VC35l were measured in all five Ω ladders; an additional nine transitions of the Ω=1 spin state were recorded in order to evaluate the V51 hyperfine structure. Hyperfine interactions associated with the C35l nucleus were not resolved, consistent with the ionic structure of the molecule. Because of extensive perturbations caused by the low-lying A Π5r excited state, the Rotational Spectrum of the ground state has been found to be quite irregular. The four lowest Ω ladders exhibit unusually large lambda-doubling interactions, with the Ω=1 component showing the largest splitting, over 2 GHz in magnitude. The Ω=1 transitions are also shifted to higher frequency relative to the other spin components. In addition, the hyperfine structure varies wi...
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the Rotational Spectrum of cof in all three spin orbit components of the xφi3 state
Journal of Chemical Physics, 2007Co-Authors: Jeremy J Harrison, P M Sheridan, John M Brown, M A Flory, S K Mclamarrah, L M ZiurysAbstract:The pure Rotational Spectrum of cobalt monofluoride in its XΦi3 electronic state has been measured in the frequency range of 256–651GHz using direct absorption techniques. CoF was created by reacting cobalt vapor with F2 in helium at low pressure (25–30mTorr). All three spin components were identified in the Spectrum of this species, two of which exhibited lambda doubling. Each spin component showed hyperfine splittings from both nuclei: an octet pattern arising from the Co59 spin of I=7∕2, which is further split into doublets due to the F19 nucleus (I=1∕2). The data were fitted close to experimental precision using an effective Hamiltonian expressed in Hund’s case (a) form, and Rotational, fine structure, hyperfine, and lambda-doubling parameters were determined. There is evidence that the Rotational levels of the highest spin component Φ23 are perturbed. The r0 bond length of CoF was estimated from the Rotational constant to be 1.738014(1)A. This value is in good agreement with previous studies but much...
