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Bermudez C, Motiyenko RA, Cabezas C, Ilyushin VV, Margulès L, Endo Y, Guillemin JC. Internal rotation analysis of the microwave and millimeter wave spectra of fluoral (CF 3CHO). Spectrochim Acta A Mol Biomol Spectrosc 2022; 274:121071. [PMID: 35276473 DOI: 10.1016/j.saa.2022.121071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Revised: 02/09/2022] [Accepted: 02/20/2022] [Indexed: 06/14/2023]
Abstract
The rotational spectrum (4-40 GHz and 50-330 GHz) has been measured and analyzed for trifluoroacetaldehyde, also known as fluoral (CF3CHO), which is one of the degradation products of the fluorinated contaminants emitted into the atmosphere. The complexity of the spectroscopic analysis of this molecule arises from the strong coupling between the internal rotation motion of CF3 group and the overall rotation of the molecule. The value obtained for its coupling constant (ρ = 0.91723481(49)) is comparable to the corresponding value of methanol (CH3OH, ρ = 0.81), which is known for its complex spectrum. A total of 12,322 transitions of the ground, the first and second excited torsional states (ΔE1υt = 62.0183(13)cm-1; ΔE2υt = 120.3315(13)cm-1) with J ≤ 50 were included in the analysis that was performed employing the rho-axis-method (RAM), and the RAM36 code. A fit within experimental error (root mean square deviation equals to 35 kHz) has been achieved for this dataset using 47 parameters of the RAM torsion-rotation Hamiltonian. In the course of the analysis, it became evident that for such high ρ value, as it is determined for fluoral, a larger than usual torsional basis set at the first diagonalization step of the two-step diagonalization procedure is required for achieving a fit within experimental error.
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Affiliation(s)
- C Bermudez
- Université de Lille, CNRS, UMR 8523 - PhLAM - Physique des Lasers Atomes et Molécules, Lille 59000, France; Grupo de Astrofísica Molecular, Instituto de Física Fundamental (IFF-CSIC), C/ Serrano 121, 28006 Madrid, Spain; Departamento de Química Física y Química Inorgánica, Facultad de Ciencias - I.U. CINQUIMA, Universidad de Valladolid, Paseo de Belén 7, Valladolid 47011, Spain.
| | - R A Motiyenko
- Université de Lille, CNRS, UMR 8523 - PhLAM - Physique des Lasers Atomes et Molécules, Lille 59000, France
| | - C Cabezas
- Grupo de Astrofísica Molecular, Instituto de Física Fundamental (IFF-CSIC), C/ Serrano 121, 28006 Madrid, Spain; Department of Applied Chemistry, Science Building II, National Yang Ming Chiao Tung University, 1001 Ta-Hsueh Rd., Hsinchu 300098, Taiwan
| | - V V Ilyushin
- Institute of Radio Astronomy of NASU, 4 Mystetstv St, Kharkiv 61002, Ukraine; Quantum Radiophysics Department, V.N. Karazin Kharkiv National University, Svobody Square 4, 61022 Kharkiv, Ukraine
| | - L Margulès
- Université de Lille, CNRS, UMR 8523 - PhLAM - Physique des Lasers Atomes et Molécules, Lille 59000, France
| | - Y Endo
- Department of Applied Chemistry, Science Building II, National Yang Ming Chiao Tung University, 1001 Ta-Hsueh Rd., Hsinchu 300098, Taiwan
| | - J-C Guillemin
- Univ Rennes, Ecole Nationale Supérieure de Chimie de Rennes, CNRS, ISCR-UMR 6226, F-35000 Rennes, France
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Ilyushin VV, Johnson AM, Hohl J, Cloessner EA, Lovas FJ, Lavrich RJ. Isotopic Dependence of the Hydrogen-Transfer-Triggered Methyl-Group Rotation in Deuterated 5-Methyltropolone. J Mol Spectrosc 2018; 343:10.1016/j.jms.2017.09.004. [PMID: 31097843 PMCID: PMC6512845 DOI: 10.1016/j.jms.2017.09.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
We present here the first experimental study of the microwave spectrum of deuterated 5-methyltropolone, a molecule which exhibits two large-amplitude motions: an intramolecular hydrogen transfer (deuterium transfer in the current case of deuterated 5-methyltropolone) and a methyl torsion. The main goal of this study was to get information on the isotopic dependence of the main tunneling parameters of 5-methyltropolone in the framework of the two dimensional tunneling formalism, which previously has shown some counterintuitive results for isotopic dependence of tunneling parameters in 2-methylmalonaldehyde. Measurements were carried out by Fourier-transform microwave spectroscopy in the 9 GHz to 26 GHz frequency range. Theoretical analysis was carried out using a tunneling-rotational Hamiltonian based on a G12 m extended-group-theory formalism. Our global fit of 384 transitions to 17 molecular parameters gave a weighted root-mean-square deviation of 0.8. The current study on the isotopic dependence of the main tunneling parameters in 5-methyltropolone supports the assumption of possible "leakage" between tunneling parameters in the two-dimensional tunneling formalism in use.
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Affiliation(s)
- Vadim V Ilyushin
- Institute of Radio Astronomy of NASU, Mystetstv 4, 61002 Kharkov, Ukraine
- Quantum Radiophysics Department of V.N. Karazin Kharkiv National University, Svobody Square 4, 61022, Kharkov, Ukraine
| | - Alyssa M Johnson
- Department of Chemistry and Biochemistry, College of Charleston, Charleston, SC 29424, USA
| | - Jenna Hohl
- Department of Chemistry and Biochemistry, College of Charleston, Charleston, SC 29424, USA
| | - Emily A Cloessner
- Department of Chemistry and Biochemistry, College of Charleston, Charleston, SC 29424, USA
| | - Frank J Lovas
- Sensor Science Division, National Institute of Standards and Technology, Gaithersburg, MD 20899-8441, USA
| | - Richard J Lavrich
- Department of Chemistry and Biochemistry, College of Charleston, Charleston, SC 29424, USA
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Belov SP, Golubiatnikov GY, Lapinov AV, Ilyushin VV, Alekseev EA, Mescheryakov AA, Hougen JT, Xu LH. Torsionally mediated spin-rotation hyperfine splittings at moderate to high J values in methanol. J Chem Phys 2016; 145:024307. [PMID: 27421405 DOI: 10.1063/1.4954941] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
This paper presents an explanation based on torsionally mediated proton-spin-overall-rotation interaction for the observation of doublet hyperfine splittings in some Lamb-dip sub-millimeter-wave transitions between ground-state torsion-rotation states of E symmetry in methanol. These unexpected doublet splittings, some as large as 70 kHz, were observed for rotational quantum numbers in the range of J = 13 to 34, and K = - 2 to +3. Because they increase nearly linearly with J for a given branch, we confined our search for an explanation to hyperfine operators containing one nuclear-spin angular momentum factor I and one overall-rotation angular momentum factor J (i.e., to spin-rotation operators) and ignored both spin-spin and spin-torsion operators, since they contain no rotational angular momentum operator. Furthermore, since traditional spin-rotation operators did not seem capable of explaining the observed splittings, we constructed totally symmetric "torsionally mediated spin-rotation operators" by multiplying the E-species spin-rotation operator by an E-species torsional-coordinate factor of the form e(±niα). The resulting operator is capable of connecting the two components of a degenerate torsion-rotation E state. This has the effect of turning the hyperfine splitting pattern upside down for some nuclear-spin states, which leads to bottom-to-top and top-to-bottom hyperfine selection rules for some transitions, and thus to an explanation for the unexpectedly large observed hyperfine splittings. The constructed operator cannot contribute to hyperfine splittings in the A-species manifold because its matrix elements within the set of torsion-rotation A1 and A2 states are all zero. The theory developed here fits the observed large doublet splittings to a root-mean-square residual of less than 1 kHz and predicts unresolvable splittings for a number of transitions in which no doublet splitting was detected.
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Affiliation(s)
- S P Belov
- Institute of Applied Physics of the Russian Academy of Sciences, 46 Ulyanov Street, 603950 Nizhny Novgorod, Russia
| | - G Yu Golubiatnikov
- Institute of Applied Physics of the Russian Academy of Sciences, 46 Ulyanov Street, 603950 Nizhny Novgorod, Russia
| | - A V Lapinov
- Institute of Applied Physics of the Russian Academy of Sciences, 46 Ulyanov Street, 603950 Nizhny Novgorod, Russia
| | - V V Ilyushin
- Institute of Radio Astronomy of National Academy of Sciences of Ukraine, Chervonopraporna 4, 61002 Kharkov, Ukraine
| | - E A Alekseev
- Institute of Radio Astronomy of National Academy of Sciences of Ukraine, Chervonopraporna 4, 61002 Kharkov, Ukraine
| | - A A Mescheryakov
- Institute of Radio Astronomy of National Academy of Sciences of Ukraine, Chervonopraporna 4, 61002 Kharkov, Ukraine
| | - J T Hougen
- Sensor Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8441, USA
| | - Li-Hong Xu
- Department of Physics and Centre for Laser, Atomic, and Molecular Sciences, University of New Brunswick, Saint John, New Brunswick E2L 4L5, Canada
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Rajappan Nair KP, Jahn MK, Lesarri A, Ilyushin VV, Grabow JU. Six-fold-symmetry internal rotation in toluenes: the low barrier challenge of 2,6- and 3,5-difluorotoluene. Phys Chem Chem Phys 2015; 17:26463-70. [DOI: 10.1039/c5cp03751d] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Pure six-fold symmetry (V6) internal rotation poses significant challenges to experimental and theoretical determination, as the very low torsional barriers result in huge tunneling splittings difficult to identify and to model.
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Affiliation(s)
- K. P. Rajappan Nair
- Institut für Physikalische Chemie und Elektrochemie
- Gottfried Wilhelm Leibniz Universität Hannover
- Callinstraße 3A
- 30167 Hannover
- Germany
| | - Michaela K. Jahn
- Institut für Physikalische Chemie und Elektrochemie
- Gottfried Wilhelm Leibniz Universität Hannover
- Callinstraße 3A
- 30167 Hannover
- Germany
| | - Alberto Lesarri
- Departamento de Química Física y Química Inorgánica
- Facultad de Ciencias
- Universidad de Valladolid
- 47011 Valladolid
- Spain
| | - Vadim V. Ilyushin
- Institute of Radio Astronomy of NASU
- Chervonopraporna 4
- 61002 Kharkov
- Ukraine
| | - Jens-Uwe Grabow
- Institut für Physikalische Chemie und Elektrochemie
- Gottfried Wilhelm Leibniz Universität Hannover
- Callinstraße 3A
- 30167 Hannover
- Germany
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5
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Ilyushin VV, Cloessner EA, Chou YC, Picraux LB, Hougen JT, Lavrich R. A microwave study of hydrogen-transfer-triggered methyl-group rotation in 5-methyltropolone. J Chem Phys 2010; 133:184307. [PMID: 21073223 DOI: 10.1063/1.3493336] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present here the first experimental and theoretical study of the microwave spectrum of 5-methyltropolone, which can be visualized as a seven-membered "aromatic" carbon ring with a five-membered hydrogen-bonded cyclic structure at the top and a methyl group at the bottom. The molecule is known from earlier studies in the literature to exhibit two large-amplitude motions, an intramolecular hydrogen transfer and a methyl torsion. The former motion is particularly interesting because transfer of the hydrogen atom from the hydroxyl to the carbonyl group induces a tautomerization in the molecule, which then triggers a 60° internal rotation of the methyl group. Measurements were carried out by Fourier-transform microwave spectroscopy in the 8-24 GHz frequency range. Theoretical analysis was carried out using a tunneling-rotational Hamiltonian based on a G(12)(m) extended-group-theory formalism. Our global fit of 1015 transitions to 20 molecular parameters gave a root-mean-square deviation of 1.5 kHz. The tunneling splitting of the two J=0 levels arising from a hypothetical pure hydrogen-transfer motion is calculated to be 1310 MHz. The tunneling splitting of the two J=0 levels arising from a hypothetical pure methyl top internal-rotation motion is calculated to be 885 MHz. We have also carried out ab initio calculations, which support the structural parameters determined from our spectroscopic analysis and give estimates of the barriers to the two large-amplitude motions.
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Affiliation(s)
- Vadim V Ilyushin
- Institute of Radio Astronomy of NASU, Chervonopraporna 4, 61002 Kharkov, Ukraine
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Ilyushin VV, Favero LB, Caminati W, Grabow JU. Intertorsional Interactions Revealing Absolute Configurations: The V6 Internal Rotation Heavy-Top Case of Benzotrifluoride. Chemphyschem 2010; 11:2589-93. [DOI: 10.1002/cphc.201000223] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Plusquellic DF, Kleiner I, Demaison J, Suenram RD, Lavrich RJ, Lovas FJ, Fraser GT, Ilyushin VV. The microwave spectrum of a two-top peptide mimetic: The N-acetyl alanine methyl ester molecule. J Chem Phys 2006; 125:104312. [PMID: 16999531 DOI: 10.1063/1.2348871] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The rotational spectrum of N-acetyl alanine methyl ester, a derivative of the biomimetic, N-acetyl alanine N'-methyl amide or alanine dipeptide, has been measured using a mini Fourier transform spectrometer between 9 and 25 GHz as part of a project undertaken to determine the conformational structures of various peptide mimetics from the torsion-rotation parameters of low-barrier methyl tops. Torsion-rotation splittings from two of the three methyl tops capping the acetyl end of the -NH-C(=O)- and the methoxy end of -C(=O)-O- groups account for most of the observed lines. In addition to the AA state, two E states have been assigned and include an AE state having a torsional barrier of 396.45(7) cm(-1) (methoxy rotor) and an EA state having a barrier of 64.96(4) cm(-1) (acetyl rotor). The observed torsional barriers and rotational constants of alanine dipeptide and its methyl ester are compared with predictions from Möller-Plesset second-order perturbation theory (MP2) and density functional theory (DFT) in an effort to explore systematic errors at the two levels of theory. After accounting for zero-point energy differences, the torsional barriers at the MP2/cc-pVTZ level are in excellent agreement with experiment for the acetyl and methoxy groups while DFT predictions range from 8% to 80% too high or low. DFT is found to consistently overestimate the overall molecular size while MP2 methods give structures that are undersized. Structural discrepancies of similar magnitude are evident in previous DFT results of crystalline peptides.
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Affiliation(s)
- David F Plusquellic
- Optical Technology Division, National Institute of Standards and Technology, Gaithersburg, MD 20899-8441, USA.
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8
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Baskakov OI, Ilyushin VV, Alekseev EA, Bürger H, Pawelke G. High-Resolution Infrared Study of the nu(7), nu(8), and nu(15) Bands and Millimeter-Wave Investigation of the v(8) = 1 State of CF(2)Cl-CH(3). J Mol Spectrosc 2000; 202:285-292. [PMID: 10877959 DOI: 10.1006/jmsp.2000.8130] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
High-resolution (Deltavarsigma = 2.3 and 2.9 x 10(-3) cm(-1)) FTIR spectra of natural and (35)Cl monoisotopic CH(3)CF(2)Cl have been recorded at -70 degrees C in the 600-1400 cm(-1) range. The bands nu(7), nu(8), and nu(15) have been rotationally analyzed for both isotopic varieties. With the help of predictions based on nu(8) parameters, the millimeter-wave spectrum of the (35)Cl species in the v(8) = 1 state has been observed and jointly fitted with the IR data. Only a small number of local perturbations have been detected in the spectra. Altogether more than 8000 IR transitions have been fitted with an experimental precision of ca. 3 x 10(-4) cm(-1). Copyright 2000 Academic Press.
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Affiliation(s)
- OI Baskakov
- Faculty of Quantum Radiophysics, Kharkov State University, Kharkov, 310077, Ukraine
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Baskakov OI, Dyubko SF, Katrich AA, Ilyushin VV, Alekseev EA. Millimeter-Wave Spectrum of CF(2)Cl(2), Taking into Account the Hyperfine Structure. J Mol Spectrosc 2000; 199:26-33. [PMID: 10712867 DOI: 10.1006/jmsp.1999.7981] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A new investigation of the CF(2)(35)Cl(2) ground state rotational spectrum in the 50-100 GHz frequency range gave an opportunity to improve the accuracy of rotational and quartic distortion parameters by an order of magnitude and to determine values of six sextic centrifugal distortion parameters. A special technique was used to process line profiles of unresolved or partially resolved hyperfine structures of rotational transitions. It allowed us to improve significantly values for the diagonal parameters of quadrupole coupling chi(aa), (chi(bb)-chi(cc)) and to determine the off-diagonal parameter chi(ab). Copyright 2000 Academic Press.
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Affiliation(s)
- OI Baskakov
- Faculty of Quantum Radiophysics, Kharkov State University, Svobody Sq. 4, Kharkov, 310077, Ukraine
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Ilyushin VV, Alekseev EA, Dyubko SF, Baskakov OI. Microwave Spectroscopy of the Ground, nu18, 2nu18, and nu11 Vibrational States of CF3CFH2. J Mol Spectrosc 1999; 195:246-255. [PMID: 10329268 DOI: 10.1006/jmsp.1999.7825] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The rotational spectra of the ground, nu18, 2nu18, and nu11 vibrational states of CF3CFH2 have been investigated in the frequency range 48-116 GHz with an accuracy of measurement better than 10 kHz. Rotational and centrifugal distortion parameters derived using an S-reduced Watson-type Hamiltonian have been improved for the ground and nu18 states. An interaction between 2nu18 and nu11 vibrational states has been detected, and rotational, centrifugal distortion, and coupling parameters of these states have been determined for the first time. The wavenumber difference between the 2nu18 and nu11 states was found to be 11.20996(54) cm-1. Copyright 1999 Academic Press.
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Affiliation(s)
- VV Ilyushin
- Institute of Radio Astronomy of NASU, Krasnoznamennaya 4, Kharkov, 310002, Ukraine
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