2,372 results on '"Fermi resonance"'
Search Results
102. Vibrational quasi-degenerate perturbation theory with optimized coordinates: Applications to ethylene and trans-1,3-butadiene
- Author
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Otaki, Hiroki [Theoretical Molecular Science Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan)]
- Published
- 2014
- Full Text
- View/download PDF
103. Mode Selective Vibrational Redistribution and Unimolecular Reactions During and After Ir—Laser Excitation
- Author
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Quack, Martin, Jortner, J., editor, Levine, R. D., editor, and Pullman, B., editor
- Published
- 1991
- Full Text
- View/download PDF
104. Infrared Spectra of H-Bonded Molecules
- Author
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Marechal, Y., Dore, John C., editor, and Teixeira, José, editor
- Published
- 1991
- Full Text
- View/download PDF
105. Properties of H-Bonding in the Infrared Spectral Range
- Author
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Bratos, S., Ratajczak, H., Viot, P., Dore, John C., editor, and Teixeira, José, editor
- Published
- 1991
- Full Text
- View/download PDF
106. Anomalous vibrational modes in acetanilide: a F.D.S. incoherent inelastic neutron scattering study
- Author
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Barthes, Mariette, Eckert, Juergen, Johnson, Susanna W., Moret, Jacques, Swanson, Basil I., Unkefer, Clifford J., Araki, H., editor, Ehlers, J., editor, Hepp, K., editor, Jaffe, R. L., editor, Kippenhahn, R., editor, Ruelle, D., editor, Weidenmüller, H. A., editor, Wess, J., editor, Zittartz, J., editor, Beiglböck, W., editor, Remoissenet, M., editor, and Peyrand, M., editor
- Published
- 1991
- Full Text
- View/download PDF
107. Determination of temperature-dependent Fermi resonance in acetonitrile-water binary solution by two-dimensional correlation Raman spectroscopy
- Author
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Ying Wang, Shenghan Wang, Chenglin Sun, Zhiwei Men, Lu Xing, and Xianwen Cao
- Subjects
Phase transition ,Materials science ,Anharmonicity ,Analytical chemistry ,General Physics and Astronomy ,Electron ,Electrolyte ,Ion ,symbols.namesake ,symbols ,Molecule ,Fermi resonance ,Physical and Theoretical Chemistry ,Raman spectroscopy - Abstract
Acetonitrile (AN), as an organic solvent, has a wide range of applications. The C≡N stretching vibration mode (ν2) and the combination mode (ν3 + ν4) are coupled by Fermi resonance (FR). In this work, the phase transition and the interaction mechanism of the 60% AN–water binary solution (AN–Water) were analyzed by calculating FR parameters and two-dimensional correlation Raman spectroscopy (2DCRS). The change in the ν2 band and the base bands ν3 and ν4 caused energy transfer by anharmonic interaction, which led to a change in FR parameters. With a reduced temperature, the energy transfer was caused by microheterogeneity and the energy transfer effect (293–273 K), the phase separation (263–233 K), and the phase transition of AN (223–173 K). The 2DCRS and Gaussian deconvolution provided more information on FR, which revealed the interaction mechanism of the Fermi doublet. The polarity and binding modes of molecules provided a new perspective for analyzing the transmission of electrons and ions in the electrolyte at different temperatures.
- Published
- 2021
108. On the 'Matsubara heating' of overtone intensities and Fermi splittings
- Author
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Stuart C. Althorpe, Raz L. Benson, Benson, Raz [0000-0002-9746-1860], Althorpe, Stuart [0000-0003-1288-8070], and Apollo - University of Cambridge Repository
- Subjects
Physics ,Coupling ,34 Chemical Sciences ,Overtone ,General Physics and Astronomy ,Molecular dynamics ,3407 Theoretical and Computational Chemistry ,Amplitude ,5102 Atomic, Molecular and Optical Physics ,Quantum mechanics ,3406 Physical Chemistry ,Fermi resonance ,Physical and Theoretical Chemistry ,Perturbation theory ,Quantum ,51 Physical Sciences ,Order of magnitude - Abstract
Classical molecular dynamics (MD) and imaginary-time path-integral dynamics methods underestimate the infrared absorption intensities of overtone and combination bands by typically an order of magnitude. Ple et al. [J. Chem. Phys. 155, 104108 (2021)] have shown that this is because such methods fail to describe the coupling of the centroid to the Matsubara dynamics of the fluctuation modes; classical first-order perturbation theory (PT) applied to the Matsubara dynamics is sufficient to recover most of the lost intensity in simple models and gives identical results to quantum (Rayleigh–Schrodinger) PT. Here, we show numerically that the results of this analysis can be used as post-processing correction factors, which can be applied to realistic (classical MD or path-integral dynamics) simulations of infrared spectra. We find that the correction factors recover most of the lost intensity in the overtone and combination bands of gas-phase water and ammonia and much of it for liquid water. We then re-derive and confirm the earlier PT analysis by applying canonical PT to Matsubara dynamics, which has the advantage of avoiding secular terms and gives a simple picture of the perturbed Matsubara dynamics in terms of action-angle variables. Collectively, these variables “Matsubara heat” the amplitudes of the overtone and combination vibrations of the centroid to what they would be in a classical system with the oscillators (of frequency Ωi) held at their quantum effective temperatures [of ℏΩi coth(βℏΩi/2)/2kB]. Numerical calculations show that a similar neglect of “Matsubara heating” causes path-integral methods to underestimate Fermi resonance splittings.
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- 2021
- Full Text
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109. Spectroscopic Manifestations of Indirect Vibrational State Mixing: Novel Anharmonic Effects on a Prereactive H Atom Transfer Surface
- Author
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Timothy S. Zwier, Karl N. Blodgett, and Edwin L. Sibert
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Chemistry ,Excited state ,Anharmonicity ,Degenerate energy levels ,Vibrational energy relaxation ,Infrared spectroscopy ,Density functional theory ,Fermi resonance ,Physical and Theoretical Chemistry ,Molecular physics ,Spectral line - Abstract
The NH stretch region of the IR spectrum of methyl anthranilate is modeled in the S1 state to understand the connection between the absence of this fundamental in the fluorescence-dip infrared spectra of Blodgett et al. [Phys. Chem. Chem. Phys.2020, 22, 14077] and its relevance to the H atom dislocation that occurs upon electronic excitation. A set of coordinates are chosen that highlight the role of certain low-frequency modes. A Hamiltonian is developed in which a large-amplitude two-dimensional surface describing the H-bonded H atom is linearly and quadratically coupled to the remaining degrees of freedom which are treated at the harmonic level. The surface is calculated within the time-dependent density functional theory framework by using the B3LYP/6-311++(d, p) level of theory with dispersion. Our spectral results show that indirect couplings lead to massive intensity sharing over hundreds of wavenumbers. This sharing is predicted to be dramatically reduced upon deuteration. The spectral broadening mechanism is found to involve off-resonant doorway states that are themselves strongly coupled to states nearly degenerate with the NH stretch fundamental and represents a complementary mechanism to previous explanations based on Fermi resonance or the presence of Franck-Condon like combination bands with low-frequency motions. Consistent with the spectra predictions, time-dependent calculations show that if the NH stretch fundamental were excited with an ultrafast laser, it would decay within 40 fs. The competition between H atom dislocation and vibrational relaxation is discussed.
- Published
- 2021
110. Incoherent Neutron Scattering and Infra-Red Measurements in Acetanilide and Derivatives
- Author
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Barthes, Mariette, Christiansen, Peter Leth, editor, and Scott, Alwyn C., editor
- Published
- 1990
- Full Text
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111. Nonlinear excitations in chains of hydrogen-bonded molecules: Incoherent neutron scattering in acetanilide and derivatives
- Author
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Barthes, M., Almairac, R., Sauvajol, J. L., Moret, J., Currat, R., Dianoux, J., Araki, H., editor, Ehlers, J., editor, Hepp, K., editor, Kippenhahn, R., editor, Ruelle, D., editor, Weidenmüller, H. A., editor, Wess, J., editor, Zittartz, J., editor, Beiglböck, W., editor, Barthes, M., editor, and Léon, J., editor
- Published
- 1990
- Full Text
- View/download PDF
112. Vibrational spectroscopy of protonated amine–water clusters: tuning Fermi resonance and lighting up dark states
- Author
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Asuka Fujii, Qian-Rui Huang, Jer-Lai Kuo, Ryunosuke Shishido, and Chih-Kai Lin
- Subjects
Coupling constant ,Materials science ,Methylamine ,Overtone ,Anharmonicity ,Ab initio ,General Physics and Astronomy ,Infrared spectroscopy ,Molecular physics ,chemistry.chemical_compound ,chemistry ,Molecular vibration ,Fermi resonance ,Physics::Chemical Physics ,Physical and Theoretical Chemistry - Abstract
Strong coupling between stretching fundamentals and bending overtones of vibrational modes, known as Fermi resonance (FR), has been observed for proton motions in the protonated trimethylamine-water cluster. To investigate the role of FR, we examined the vibrational spectra of other three protonated ammonia/amine-water clusters, including the NH4+ ion and its mono- and di-methylated analogues, respectively, with and without argon tagging. In these systems, a simple frequency-scaled harmonic oscillator model will predict only one strong band between 2600 and 3200 cm-1 uniquely due to the hydrogen-bonded NH stretching fundamental for a given conformer. In the experimental vibrational spectra, however, multiple sharp bands were observed. Such a discrepancy often leads to the notions of the coexistence of multiple conformers and/or the appearance of an overtone state as a result of FR. In this work, we applied a discrete variable representation (DVR) implementation of ab initio anharmonic algorithms and demonstrated how one N-H+ stretching fundamental can lead to multiple bands as a result of intrinsic anharmonic couplings. A prominent effect of tuning these FR bands and lighting up dark overtone states in this wide frequency range was investigated by changing the number of methyl groups in the protonated amine moiety. The effect of Ar-tagging was also analyzed and decent agreement between the experimental and simulated spectra certified the above-mentioned simple pictures. We also found that the coupling constant for trimethylamine is the largest among these protonated amine-water clusters, and the overall coupling strength decreases as the hydrogen-bonded NH stretching frequency redshifts in the order of dimethylamine, methylamine, and ammonia.
- Published
- 2020
- Full Text
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113. Structural characterization and Raman spectrum of Cs[OCN]
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Francis J. DiSalvo, Olaf Reckeweg, and Armin Schulz
- Subjects
Crystallography ,symbols.namesake ,Materials science ,Lattice (order) ,Triatomic molecule ,symbols ,Moiety ,General Chemistry ,Fermi resonance ,Crystal structure ,Alkali metal ,Raman spectroscopy ,Ion - Abstract
The compound Cs[OCN] has been synthesized and its crystal structure and Raman spectrum were determined on selected single crystals. As postulated in earlier work, the title compound crystallizes isopointal to KN3 exhibiting the space group I4/mcm (no. 140, Z = 4) with the lattice parameters a = 653.79(2) and c = 799.42(5) pm. The Raman spectrum verified the nature of the triatomic moiety and shows the frequencies typical for an [OCN]− anion with Fermi resonance between the 2δ and the ν sym vibrations. The undisturbed frequencies and the resulting force constants have been calculated and compared to those of other alkali metal compounds containing comparable linear triatomic anions.
- Published
- 2019
- Full Text
- View/download PDF
114. Nucleoside conformers in low-temperature argon matrices: Fourier transform IR spectroscopy of isolated thymidine and deuterothymidine molecules and quantum-mechanical calculations
- Author
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A. Yu. Ivanov, Ludwik Adamowicz, Stepan G. Stepanian, and Victor A. Karachevtsev
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010302 applied physics ,education.field_of_study ,Materials science ,Physics and Astronomy (miscellaneous) ,Hydrogen bond ,Population ,General Physics and Astronomy ,Infrared spectroscopy ,01 natural sciences ,Crystallography ,Absorption band ,Intramolecular force ,0103 physical sciences ,Molecule ,Fermi resonance ,010306 general physics ,education ,Conformational isomerism - Abstract
The conformational equilibrium of thymidine and deuterothymidine molecules in low-temperature Ar matrices has been studied using low-temperature matrix-isolation Fourier IR spectroscopy and quantum-chemical calculations by the DFT/B3LYP and MP2 methods. It has been found that two anti-conformers ta2_0 and ta3_0 with different structures of the sugar ring, C2′-endo and C3′-endo, predominate in low-temperature matrices. In isolated state, each of these conformers has a few low-barrier satellites that can fully pass into more stable structures when a molecule enters the matrix. The main syn conformer ts2_0 is stabilized by an intramolecular hydrogen bond between the O5′H group of the sugar and the C2O group of the base (O5′H⋅⋅⋅O2), while C2′-endo is the predominant conformation of the deoxyribose ring. The considerably lower population of ts2_0 compared to the anti-conformers ta2_0, ta3_0 can be explained by the smaller population of satellite conformations. It has been shown that the absorption band of νN3D stretching vibration is split by the Fermi resonance.
- Published
- 2019
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115. The Role of Fermi and Darling–Dennison Resonances in the Formation of the Raman Spectra of Water and Water–Ethanol Solutions
- Author
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Sergey A. Burikov, Tatiana A. Dolenko, Sergey Dolenko, and Ivan V. Plastinin
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010302 applied physics ,Physics ,Optimization algorithm ,010308 nuclear & particles physics ,Hadron ,General Physics and Astronomy ,01 natural sciences ,Spectral line ,symbols.namesake ,0103 physical sciences ,symbols ,Fermi resonance ,Atomic physics ,Raman spectroscopy ,Physics::Atmospheric and Oceanic Physics ,Fermi Gamma-ray Space Telescope - Abstract
Experimental studies show that Fermi and Darling–Dennison resonances make substantial contribution to the formation of Raman spectra of water and water–ethanol solutions. Based on the analysis of spectra with an optimization algorithm, constants of interactions W and contributions of Fermi resonance to Raman spectra of water and water–ethanol solutions are calculated at 25°C.
- Published
- 2019
- Full Text
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116. Dinitrogen Coupling to a Terpyridine-Molybdenum Chromophore Is Switched on by Fermi Resonance
- Author
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Paul J. Chirik, Shahnawaz Rafiq, Gregory D. Scholes, and Máté J. Bezdek
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Materials science ,General Chemical Engineering ,Biochemistry (medical) ,02 engineering and technology ,General Chemistry ,Chromophore ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Kinetic energy ,01 natural sciences ,Biochemistry ,0104 chemical sciences ,chemistry.chemical_compound ,Chemical bond ,chemistry ,Chemical physics ,Materials Chemistry ,Environmental Chemistry ,Chemical stability ,Fermi resonance ,Terpyridine ,0210 nano-technology ,Rotational–vibrational coupling ,Coherence (physics) - Abstract
Summary The traditional view of a chemical change is inherently local and classical, and such a change relies on a mix of thermodynamic and kinetic parameters to control reactivity. Often, the thermodynamic stability of chemical bonds necessitates significant energy input for activation. One fundamental question is potentially transformative: can quantum mechanics enable selective bond activation? A possible approach involves strategic input of energy to reaction-specific vibrational levels. Toward this goal, our work describes the coupling of vibrational motions in a terpyridine-molybdenum complex hosting a nonreactive substrate—dinitrogen. Ultrafast coherence spectroscopies revealed a Fermi-resonance coupling mechanism connecting in-plane breathing motion of the light-harvesting terpyridines with the stretching motion of the spatially disparate dinitrogen bridge. Notably, the coupling is significantly enhanced in the photoexcited state. This Fermi resonance indicates an energy conduit that drives the two motions in sync and thereby amplifies vibrational energy exchange. Achieving selective bond activation by bridging vibrations could present a quantum-inspired design principle in synthetic chemistry.
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- 2019
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117. Aggregation induced spectral splitting and Fermi resonance of Ethylene Carbonate in binary mixture.
- Author
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Wang, Zian, Yu, Keji, Zhao, Yanying, Xue, Jiadan, Jiang, Caiying, Wang, Huigang, and Wu, Huizhen
- Subjects
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ETHYLENE carbonates , *RESONANCE , *VIBRATIONAL spectra , *RAMAN spectroscopy , *BINARY mixtures - Abstract
[Display omitted] • Four frequencies have been observed in the iso and aniso Raman spectra of EC. • Fermi constant W, NCE value V1 and V2 have been determined at different concentration. • Dimer structure and DFT calculations can reproduce the NCE and concentration effects. The vibration band of the ring stretching (ν 14), the fundamental ring breathing (ν 17) and the Fermi resonance band of carbonyl stretching mixing with the overtone of the ring breathing (ν 5 + 2ν 17) have been investigated in solid ethylene carbonate (EC) and EC/CH 3 CN and EC/CHCl 3 binary mixture. Dimer structure with aggregation-induced spectral splitting model (AIS) was applied to calculate the vibration spectra using the B3LYP-D3/6-311+G (d,p) procedure. The noncoincidence effect (NCE) and concentration induced frequency shifts of the ν 14 and ν 5 could be well explained by AIS model based on the dimer structure. Four bands were observed with two in the isotropic and two in the anisotropic Raman spectra and their NCE value decreased with the decrease of EC volume fraction in the binary mixture, and finally disappeared. NCE value and the Fermi resonance constants of EC at different concentrations were calculated from the experimental data. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
118. Calculation of vibrational eigenenergies on a quantum computer: Application to the Fermi resonance in CO2
- Author
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Yutaka Tachikawa, Kaoru Yamanouchi, Takashi Tsuchiya, and Erik Lötstedt
- Subjects
Physics ,Matrix (mathematics) ,Hamiltonian matrix ,Qubit ,Quantum mechanics ,Fermi resonance ,Wave function ,Energy (signal processing) ,Eigenvalues and eigenvectors ,Quantum computer - Abstract
We apply a modified version of the multistate contracted variational quantum eigensolver method to calculate vibrational eigenstates of ${\mathrm{CO}}_{2}$ on a quantum computer. A two-mode model of ${\mathrm{CO}}_{2}$ is employed, and the vibrational wave function is expanded using three harmonic-oscillator basis functions for each mode. The wave functions are mapped to four qubits by a compact mapping method. The Hamiltonian matrix elements are evaluated on a simulator including noise and on a quantum computer available at IBM Quantum, while the Hamiltonian matrix is diagonalized on a classical computer. We propose an error mitigation method by which the shift of the numerical values of the matrix elements originating from the noise can be corrected, and examine the dependence of the statistical uncertainties on the number of executions of each quantum circuit. We find that, at about $8\ifmmode\times\else\texttimes\fi{}{10}^{6}$ executions, the energy eigenvalues of the Fermi resonance states in ${\mathrm{CO}}_{2}$ can be obtained with an uncertainty within 1 ${\mathrm{cm}}^{\ensuremath{-}1}$.
- Published
- 2021
- Full Text
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119. Intermolecular Interactions at the Silica-Liquid Interface Modulate the Fermi Resonance Coupling in Surface Methanol
- Author
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Luis Velarde, Luis A. Colón, and Thomas T. Bui
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Materials science ,Intermolecular force ,Solvation ,Analytical chemistry ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Mole fraction ,01 natural sciences ,0104 chemical sciences ,Solvent ,chemistry.chemical_compound ,chemistry ,General Materials Science ,Methanol ,Fermi resonance ,Physical and Theoretical Chemistry ,0210 nano-technology ,Spectroscopy ,Acetonitrile - Abstract
The buried solid/liquid interface between hydrophilic fused silica and binary solvent mixtures of acetonitrile (MeCN) and methanol (MeOH) was studied with vibrational sum-frequency generation (vSFG) spectroscopy. Our data showed that at high relative concentrations of methanol, the Fermi resonance peak in the vSFG spectrum is greatly suppressed, and it progressively gains intensity as methanol is diluted with perdeuterated acetonitrile. This phenomenon is quantified by the Fermi resonance coupling coefficient, W, extracted using a two-level model, as well as the experimental intensity ratio, R, of the methyl Fermi resonance band to that of the symmetric stretch. At a 1.0 MeOH mole fraction, W and R values were 10 ± 10 cm-1 and 0.01 ± 0.02, respectively, whereas at a 0.1 mole fraction, W and R increased to 46 ± 4 cm-1 and 0.43 ± 0.16, respectively. This indicates that solvation with acetonitrile effectively tunes the Fermi coupling of methanol vibrations at the silica/liquid interface.
- Published
- 2021
120. Accuracy and Reliability in the Simulation of Vibrational Spectra: A Comprehensive Benchmark of Energies and Intensities Issuing From Generalized Vibrational Perturbation Theory to Second Order (GVPT2)
- Author
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Qin Yang, Marco Mendolicchio, Vincenzo Barone, Julien Bloino, Yang, Qin, Mendolicchio, Marco, Barone, Vincenzo, and Bloino, Julien
- Subjects
Astronomy ,Geophysics. Cosmic physics ,QB1-991 ,Context (language use) ,Electronic structure ,010402 general chemistry ,01 natural sciences ,benchmark ,0103 physical sciences ,Statistical physics ,Perturbation theory ,infrared spectroscopy ,second-order vibrational perturbation theory ,Fermi resonance ,density functional theory ,Basis set ,Reliability (statistics) ,Settore CHIM/02 - Chimica Fisica ,Physics ,basis set ,010304 chemical physics ,QC801-809 ,anharmonicity ,Anharmonicity ,Astronomy and Astrophysics ,Darling-Dennison resonances ,basis sets ,0104 chemical sciences ,Characterization (materials science) ,Density functional theory - Abstract
Vibrational spectroscopy represents an active frontier for the identification and characterization of molecular species in the context of astrochemistry and astrobiology. As new missions will provide more data over broader ranges and at higher resolution, especially in the infrared region, which could be complemented with new spectrometers in the future, support from laboratory experiments and theory is crucial. In particular, computational spectroscopy is playing an increasing role in deepening our understanding of the origin and nature of the observed bands in extreme conditions characterizing the interstellar medium or some planetary atmospheres, not easily reproducible on Earth. In this connection, the best compromise between reliability, feasibility and ease of interpretation is still a matter of concern due to the interplay of several factors in determining the final spectral outcome, with larger molecular systems and non-covalent complexes further exacerbating the dichotomy between accuracy and computational cost. In this context, second-order vibrational perturbation theory (VPT2) together with density functional theory (DFT) has become particularly appealing. The well-known problem of the reliability of exchange-correlation functionals, coupled with the treatment of resonances in VPT2, represents a challenge for the determination of standardized or "black-box" protocols, despite successful examples in the literature. With the aim of getting a clear picture of the achievable accuracy and reliability of DFT-based VPT2 calculations, a multi-step study will be carried out here. Beyond the definition of the functional, the impact of the basis set and the influence of the resonance treatment in VPT2 will be analyzed. For a better understanding of the computational aspects and the results, a short summary of vibrational perturbation theory and the overall treatment of resonances for both energies and intensities will be given. The first part of the benchmark will focus on small molecules, for which very accurate experimental and theoretical data are available, to investigate electronic structure calculation methods. Beyond the reliability of energies, widely used for such systems, the issue of intensities will also be investigated in detail. The best performing electronic structure methods will then be used to treat larger molecular systems, with more complex topologies and resonance patterns. Vibrational spectroscopy represents an active frontier for the identification and characterization of molecular species in the context of astrochemistry and astrobiology. As new missions will provide more data over broader ranges and at higher resolution, especially in the infrared region, which could be complemented with new spectrometers in the future, support from laboratory experiments and theory is crucial. In particular, computational spectroscopy is playing an increasing role in deepening our understanding of the origin and nature of the observed bands in extreme conditions characterizing the interstellar medium or some planetary atmospheres, not easily reproducible on Earth. In this connection, the best compromise between reliability, feasibility and ease of interpretation is still a matter of concern due to the interplay of several factors in determining the final spectral outcome, with larger molecular systems and non-covalent complexes further exacerbating the dichotomy between accuracy and computational cost. In this context, second-order vibrational perturbation theory (VPT2) together with density functional theory (DFT) has become particularly appealing. The well-known problem of the reliability of exchange-correlation functionals, coupled with the treatment of resonances in VPT2, represents a challenge for the determination of standardized or “black-box” protocols, despite successful examples in the literature. With the aim of getting a clear picture of the achievable accuracy and reliability of DFT-based VPT2 calculations, a multi-step study will be carried out here. Beyond the definition of the functional, the impact of the basis set and the influence of the resonance treatment in VPT2 will be analyzed. For a better understanding of the computational aspects and the results, a short summary of vibrational perturbation theory and the overall treatment of resonances for both energies and intensities will be given. The first part of the benchmark will focus on small molecules, for which very accurate experimental and theoretical data are available, to investigate electronic structure calculation methods. Beyond the reliability of energies, widely used for such systems, the issue of intensities will also be investigated in detail. The best performing electronic structure methods will then be used to treat larger molecular systems, with more complex topologies and resonance patterns.
- Published
- 2021
- Full Text
- View/download PDF
121. Photo-fragmentation spectroscopy of benzylium and 1-phenylethyl cations
- Author
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Soorkia, Satchin [Institut des Sciences Moléculaires d’Orsay, CNRS UMR 8214, Université Paris Sud 11, 91405 Orsay Cedex (France)]
- Published
- 2014
- Full Text
- View/download PDF
122. Raman spectroscopic study of CO2 in hydrate cages.
- Author
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Chen, Litao, Lu, Hailong, and Ripmeester, John A.
- Subjects
- *
RAMAN spectroscopy , *CARBON dioxide , *HYDRATES , *CRYSTAL structure , *TETRAHYDROFURAN - Abstract
The Raman spectra of CO 2 molecules in hydrate cages was studied for structure I CO 2 hydrate and structure II tetrahydrofuran (THF)+CO 2 binary hydrate. The results obtained for sII hydrate indicated that the Fermi dyad peaks of CO 2 in the small cage of THF–CO 2 hydrate are located at 1274 cm −1 and 1380 cm −1 . Numerical fitting of the sI CO 2 hydrate Raman spectrum shows CO 2 Fermi dyad peaks in the small cage are located at 1275 cm −1 and 1382 cm −1 . The unperturbed frequencies of the symmetric stretching v 1 and overtone bending v 2 modes were calculated for CO 2 in various states. It was found that the v 1 frequency does not follow the loose cage–tight cage model for CO 2 in hydrate cages. Explanations are given as to why such a relationship is not expected in terms of the incomplete sampling of the void space of the non-spherical cages by the linear guest molecule and the contribution of H-bonding to the guest–host interactions. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
123. Effective Hamiltonians for the Fermi resonance – Interacting states of [formula omitted] molecules.
- Author
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Sarka, Kamil, Stříteská, Lucie Nová, and Ceausu-Velcescu, Adina
- Subjects
- *
HAMILTONIAN systems , *FERMI level , *MOLECULAR interactions , *VIBRATION (Mechanics) , *STATISTICAL correlation - Abstract
A global reduction theory of the vibration–rotational Hamiltonian of C 3 v closed-shell molecules, dealing with all possible anharmonic interactions in which a fundamental vibration can be involved, is presented. The effective correlation-free Hamiltonians and the corresponding matrix elements are derived. The cases studied here are (i) a fundamental band interacting with an overtone, (ii) a fundamental band interacting with a combination band. The Hamiltonian terms H 30 , H 31 , H 32 and the recommended set of parameters following from the appropriate reductions are presented. The results are provided in a form directly applicable to the analysis of spectra of the interacting states. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
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124. Fermi resonance of two vibrations with inhomogeneously broadened spectral bands. Analytical formulas and their application to H-bonded complexes of amines.
- Author
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Efimov, Yu. Ya. and Naberukhin, Yu. I.
- Subjects
- *
HYDROGEN bonding , *AMINES , *FERMI level , *VIBRATION (Mechanics) , *RAMAN spectra , *ANISOTROPY - Abstract
A general case of interaction between two oscillators of statistically distributed frequencies has been studied. The interaction between fundamental and overtone vibrations (Fermi resonance) can be a special case. The feasible, non-zero original intensity of an overtone is also considered. Frequency distributions can be any (e.g., Gaussian, Lorentzian, and a Dirac delta function). The analytical expressions are derived for band shapes in the infra-red spectra. However, the formalism developed is also applicable to calculations of the isotropic and anisotropic components of Raman spectra. The formulas have allowed us to describe the infrared spectra of several 1:1 complexes of amines with the bases available from the literature, where Fermi-doublet bands are broadened due to hydrogen bonding. It is shown that the traditional description of Fermi resonance considering only the peak frequencies and intensities of the decomposed experimental spectral contours (ignoring their form), provides incorrect results. [ABSTRACT FROM PUBLISHER]
- Published
- 2015
- Full Text
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125. Raman spectra of proton order of thin ice I h film.
- Author
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Men, Zhiwei, Fang, Wenhui, Wang, Shenghan, Li, Zhanlong, Sun, Chenglin, and Wang, Xiaojun
- Subjects
- *
RAMAN spectra , *PROTONS , *OPTICAL polarization , *VIBRATION (Mechanics) , *ICE - Abstract
The polarized Raman spectra of the upper part of a thin ice I h film were obtained in the range of 150 cm−1 to 3800 cm−1. The spectra showed clear polarization dependence; several new peaks were also observed. The longitudinaloptic-tranverseoptic (LO-TO) splitting of the mode near 220 cm−1 in the translational vibration region was experimentally confirmed at 133 K. The Fermi resonance between the bending overtone (around 3270 cm−1) and symmetry stretching fundamental (around 3350 cm−1) in the stretching vibration region appeared at nearly the same temperature. Results showed that ice XI (i.e. proton-ordered phase of ice I h) slowly formed in the upper part of a thin ice I h film without KOH as the temperature gradually decreased below 133 K. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
126. Infrared spectroscopy and ab initio study of hydrogen bonded Cl3CD·N(CH3)3 complex in the gas phase.
- Author
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Rutkowski, K.S., Melikova, S.M., Linok, O.V., Czarnik-Matusewicz, B., and Rospenk, M.
- Subjects
- *
AB initio quantum chemistry methods , *HYDROGEN bonding , *GAS phase reactions , *COMPLEX compounds , *FOURIER transform infrared spectroscopy , *RESONANCE - Abstract
FTIR spectra of the gas phase Cl 3 CD + TMA mixture have been studied at room temperature in ∼800–4000 cm −1 frequency domain. The formation of the H-bonded Cl 3 CD…TMA complex has been detected. Spectroscopic parameters of the band ascribed to the complex were evaluated. MP2 frozen core ab initio calculations have been carried out with the Pople-type 6-311++G(d,p) basis set. The equilibrium geometries and harmonic vibrational frequencies of the complex were obtained using CP-corrected gradient techniques. The ‘‘freq = anharm’’ option has been tested for Cl 3 CD monomer and Cl 3 CD…TMA complex to examine possible anharmonic effects on the vibrations localized on the proton donor. The effects of Darling–Dennison and Fermi resonances on the frequency of the stretching vibration of the CH proton donor were analyzed. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
127. Understanding Fermi resonances in the complex vibrational spectra of the methyl groups in methylamines
- Author
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G. Naresh Patwari, Li Wei Chen, Asuka Fujii, Tomoya Endo, S. Mishra, Bingbing Zhang, Yoshiyuki Matsuda, Jer-Lai Kuo, Ling Jiang, and Qian-Rui Huang
- Subjects
Materials science ,Overtone ,Anharmonicity ,Ab initio ,General Physics and Astronomy ,Molecular physics ,chemistry.chemical_compound ,symbols.namesake ,chemistry ,Potential energy surface ,symbols ,Fermi resonance ,Physical and Theoretical Chemistry ,Hamiltonian (quantum mechanics) ,Rotational–vibrational coupling ,Methyl group - Abstract
Vibrational spectra of the methyl groups in mono-methylamine (MMA), dimethylamine (DMA), and trimethylamine (TMA) monomers and their clusters were measured in three experimental set-ups to capture their complex spectral features as a result of bend/umbrella-stretch Fermi resonance (FR). Multiple bands were observed between 2800 and 3000 cm-1 corresponding to the methyl groups for MMA and DMA. On the other hand, the corresponding spectrum of TMA is relatively simple, exhibiting only four prominent bands in the same frequency window, even though TMA has a larger number of methyl groups. The discrete variable representation (DVR) based ab initio anharmonic algorithm with potential energy surface (PES) at CCSD/aug-cc-pVDZ quality is able to capture all the experimentally observed spectral features across all three amines, and the constructed vibrational Hamiltonian was used to analyze the couplings that give rise to the observed FR patterns. It was observed that the vibrational coupling among CH stretch modes on different methyl groups is weak (less than 2 cm-1) and stronger vibrational coupling is found to localize within a methyl group. In MMA and DMA, the complex feature between 2850 and 2950 cm-1 is a consequence of closely packed overtone states that gain intensities by mixing with the stretching modes. The simplification of the spectral pattern of TMA can be understood by the red-shift of the symmetric CH3 stretching modes by about 80 cm-1 relative to MMA, which causes the symmetric CH3 stretch to shift outside the FR window.
- Published
- 2021
128. Structural and chemical properties of the nitrogen-rich energetic material triaminoguanidinium 1-methyl-5-nitriminotetrazolate under pressure
- Published
- 2012
- Full Text
- View/download PDF
129. Direct imaging of the Fermi resonance interaction in para-difluorobenzene: A special insight into energy redistributions in the S{sub 1} low-energy regime
- Author
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Bing, Zhang [State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, Hubei 430071 (China) and Graduate School of the Chinese Academy of Sciences, Beijing 100049 (China)]
- Published
- 2011
- Full Text
- View/download PDF
130. High-Resolution Infrared Spectra of Spiropentane, C5H8
- Author
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Blake, Thomas
- Published
- 2011
- Full Text
- View/download PDF
131. Strongly interacting isotopic Bose-Fermi mixture immersed in a Fermi sea
- Author
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Zwierlein, Martin [Department of Physics, MIT-Harvard Center for Ultracold Atoms, and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)]
- Published
- 2011
- Full Text
- View/download PDF
132. High resolution infrared spectroscopy of [1.1.1]propellane: The region of the ν9 band
- Author
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Kirkpatrick, Robynne
- Published
- 2010
- Full Text
- View/download PDF
133. Electronic states of MgO: Spectroscopy, predissociation, and cold atomic Mg and O production
- Author
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Hochlaf, M [Laboratoire Modelisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, Universite Paris-Est, 5 Boulevard Descartes, 77454 Marne-la-Vallee (France)]
- Published
- 2010
- Full Text
- View/download PDF
134. Two-dimensional infrared study of 3-azidopyridine as a potential spectroscopic reporter of protonation state
- Author
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Cheatum, Christopher [Department of Chemistry, University of Iowa, Iowa City, Iowa 52242 (United States)]
- Published
- 2010
- Full Text
- View/download PDF
135. BCS-BEC crossover and the disappearance of Fulde-Ferrell-Larkin-Ovchinnikov correlations in a spin-imbalanced one-dimensional Fermi gas
- Author
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Zwerger, W [Physik Department, Technische Universitaet Muenchen, D-85747 Garching (Germany)]
- Published
- 2010
- Full Text
- View/download PDF
136. Anharmonic spectral features via trajectory-based quantum dynamics: a perturbative analysis of the interplay between dynamics and sampling
- Author
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Sara Bonella, Simon Huppert, Philippe Depondt, Thomas Plé, Fabio Finocchi, Institut des Nanosciences de Paris (INSP), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), and Ecole Polytechnique Fédérale de Lausanne (EPFL)
- Subjects
high-pressure ,Zero point energy ,Quantum dynamics ,molecular-dynamics ,water ,General Physics and Astronomy ,Zero-point energy ,rates ,formulation ,Perturbation theory ,Molecular dynamics ,01 natural sciences ,Quantum statistical mechanics ,Edgeworth expansion ,0103 physical sciences ,Initial value problem ,Statistical physics ,Matsubara dynamics ,Physical and Theoretical Chemistry ,010306 general physics ,Quantum ,Fermi resonance ,Physics ,010304 chemical physics ,Vibrational spectra ,Quantum effects ,time-correlation-functions ,multiple-scale analysis ,proton-transfer ,[CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry ,Path integral formulation ,Semiclassical methods ,Perturbation theory (quantum mechanics) ,vibrational-energy relaxation ,mechanics ,Coherence (physics) - Abstract
The performance of different approximate algorithms for computing anharmonic features in vibrational spectra is analyzed and compared on model and more realistic systems that present relevant nuclear quantum effects. The methods considered combine approximate sampling of the quantum thermal distribution with classical time propagation and include Matsubara dynamics, path integral dynamics approaches, linearized initial value representation, and the recently introduced adaptive quantum thermal bath. A perturbative analysis of these different methods enables us to account for the observed numerical performance on prototypes for overtones and combination bands and to draw qualitatively correct trends for the numerical results obtained for Fermi resonances. Our results prove that the unequal performances of these approaches often derive from the method employed to sample initial conditions and not, as usually assumed, from the lack of coherence in the time propagation. Furthermore, as confirmed by the analysis reported in Benson and Althorpe, J. Chem. Phys. 130, 194510 (2021), we demonstrate, both via the perturbative approach and numerically, that path integral dynamics methods fail to reproduce the intensities of these anharmonic features and follow purely classical trends with respect to their temperature behavior. Finally, the remarkably accurate performance of the adaptive quantum thermal bath approach is documented and motivated. Published under an exclusive license by AIP Publishing.
- Published
- 2021
- Full Text
- View/download PDF
137. The symmetric C-D stretching spectator mode in the H + CHD3 H2 + CD3 reaction and its effect on dynamical modeling
- Author
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Bin Zhao
- Subjects
Physics ,Operator (physics) ,Mode (statistics) ,General Physics and Astronomy ,symbols.namesake ,Heat flux ,symbols ,Fermi resonance ,Physical and Theoretical Chemistry ,Atomic physics ,Hamiltonian (quantum mechanics) ,Quantum ,Eigenvalues and eigenvectors ,Mixing (physics) - Abstract
The symmetric C–D stretching mode is a spectator mode in the H + CHD3 → H2 + CD3 reaction. Effects of multiple vibrational excitations of the CHD3 reactant are studied with the quantum transition-state (QTS) framework and an eight-dimensional (8D) model Hamiltonian developed by Palma and Clary. By including many thermal flux eigenstates, results have been obtained up to high energies, allowing the study of the symmetric C–D stretching spectator mode. A new concept of a state-specific thermal flux operator is proposed to analyze the C–D stretching spectator mode in detail, providing a new and insightful venue for studying transition-state control of chemical reactions. Furthermore, as a spectator mode, whether the C–D stretching motion can be excluded in a seven-dimensional (7D) model has not been fully interrogated, although the 7D model is a reasonable approximation and has provided accurate theoretical predictions. By comparing with available results of full-dimensional calculations, both the 7D and 8D models predict reasonably accurate results. However, the 7D model underestimates the mixing of two vibrational states that are in Fermi resonance. Despite its spectator nature, the C–D stretch is important in the dynamical modeling of chemical reaction systems affected by state mixing.
- Published
- 2021
- Full Text
- View/download PDF
138. SMALL CARBONACEOUS MOLECULES, ETHYLENE OXIDE (c-C{sub 2}H{sub 4}O) AND CYCLOPROPENYLIDENE (c-C{sub 3}H{sub 2}): SOURCES OF THE UNIDENTIFIED INFRARED BANDS?
- Published
- 2009
- Full Text
- View/download PDF
139. The ν3 − ν4 difference band contribution to the CCl4 symmetric stretch (ν1) mode.
- Author
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Gaynor, James D., Wetterer, Anna M., Valente, Edward J., and Mayer, Steven G.
- Subjects
- *
CARBON tetrachloride , *CARBON compounds spectra , *CHEMICAL synthesis , *CARBON compounds , *RAMAN spectra , *ISOMERISM - Abstract
The Raman spectrum of the symmetric stretching vibration (ν1) of liquid carbon tetrachloride observed at 295 K and reported repeatedly over the last 80 years clearly shows four of the five more abundant isotopomers at 440-470 cm−1. At the lower energy end of this spectrum, additional intensity due to isotopomeric contributions from the symmetric stretch for v = 1 → 2 (hotbands) partially overlaps the prominent v = 0 → 1 features, and accounts for about 18% of the integrated intensity at 295 K in agreement with theory. When these two patterns are modeled and subtracted from the experimental spectrum, a feature underlying almost exactly the C35Cl4 (v = 0 → 1) band at 462.5 cm−1 becomes apparent. We propose that this feature is the ν3 − ν4 difference band. Observations at lower temperatures, and of the combination bands, and the polarized Raman spectra are consistent with this hypothesis. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
140. Analytic model of vibrations of a carbon dioxide molecule. Fermi resonance.
- Author
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Aldoshin, G. and Yakovlev, S.
- Abstract
We use the invariant normalization method to study nonlinear autonomous vibrations of a CO molecule near its stable configuration. If the frequencies of symmetric and deformation vibrations are related as 2: 1, then a third-order resonance occurs in the molecule. The simulation discovered the following two nonlinear effects: the energy transfer between modes of longitudinal and transverse vibration modes which participate in the resonance and the frequency splitting in the molecule spectrum; namely, instead of one line of symmetric vibration, there is a group of four closely located lines. These effects are known as the Fermi resonance phenomenon. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
141. First-Principles Study of Anharmonic Lattice Dynamics in Low Thermal Conductivity AgCrSe2 : Evidence for a Large Resonant Four-Phonon Scattering
- Author
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R. Li, Lin Xie, Jiaqing He, and J. H. Feng
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Physics ,Phonon scattering ,Condensed matter physics ,Phonon ,Scattering ,Anharmonicity ,General Physics and Astronomy ,01 natural sciences ,Omega ,Brillouin zone ,Condensed Matter::Materials Science ,Condensed Matter::Superconductivity ,0103 physical sciences ,Condensed Matter::Strongly Correlated Electrons ,Fermi resonance ,Perturbation theory ,010306 general physics - Abstract
We report a study of the anharmonic lattice dynamics in low lattice thermal conductivity (${\mathbit{\ensuremath{\kappa}}}_{\mathbit{l}}$) material ${\mathrm{AgCrSe}}_{2}$ by many-body perturbation theory. We demonstrate surprisingly giant four-phonon scattering exclusive for the heat-carrying transverse acoustic phonons due to large quartic anharmonicity and nondispersive phonon band structure, which lead to four-phonon Fermi resonance and breaks the classical ${\mathbit{\ensuremath{\tau}}}^{\ensuremath{-}1}\ensuremath{\sim}{\mathbit{\ensuremath{\omega}}}^{\mathbit{m}}{\mathbit{T}}^{\mathbit{n}}$ relation for phonon-phonon interactions. This strong resonant scattering extends over the Brillouin zone and substantially suppresses the thermal transport, even down to a low temperature of 100 K. The present results provide fundamental insights into the four-phonon resonant dynamics in the low-${\mathbit{\ensuremath{\kappa}}}_{\mathbit{l}}$ system with flat phonon dispersions, i.e., cuprous halides and skutterudites.
- Published
- 2020
- Full Text
- View/download PDF
142. Dynamical traps lead to the slowing down of intramolecular vibrational energy flow.
- Author
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Manikandan, Paranjothy and Keshavamurthy, Srihari
- Subjects
- *
INTRAMOLECULAR forces , *VIBRATIONAL redistribution (Molecular physics) , *QUANTUM theory , *ANISOTROPY , *MOLECULAR dynamics - Abstract
The phenomenon of intramolecular vibrational energy redistribution (IVR) is at the heart of chemical reaction dynamics. Statistical rate theories, assuming instantaneous IVR, predict exponential decay of the population with the properties of the transition state essentially determining the mechanism. However, there is growing evidence that IVR competes with the reaction timescales, resulting in deviations from the exponential rate law. Dynamics cannot be ignored in such cases for understanding the reaction mechanisms. Significant insights in this context have come from the state space model of IVR, which predicts power law behavior for the rates with the power law exponent, an effective state space dimensionality, being a measure of the nature and extent of the IVR dynamics. However, whether the effective IVR dimensionality can vary with time and whether the mechanism for the variation is of purely quantum or classical origins are issues that remain unresolved. Such multiple power law scalings can lead to surprising mode specificity in the system, even above the threshold for facile IVR. In this work, choosing the well-studied thiophosgene molecule as an example, we establish the anisotropic and anomalous nature of the quantum IVR dynamics and show that multiple power law scalings do manifest in the system. More importantly, we show that the mechanism of the observed multiple power law scaling has classical origins due to a combination of trapping near resonance junctions in the network of classical nonlinear resonances at short to intermediate times and the influence of weak higher-order resonances at relatively longer times. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
143. Vibrational spectroscopic signatures of hydrogen bond induced NH stretch-bend Fermi-resonance in amines: The methylamine clusters and other N-H⋯N hydrogen-bonded complexes
- Author
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Qian-Rui Huang, G. Naresh Patwari, Ha-Quyen Nguyen, Chih-Kai Lin, Jer-Lai Kuo, and S. Mishra
- Subjects
Quantitative Biology::Biomolecules ,Materials science ,010304 chemical physics ,Hydrogen bond ,Dimer ,Intermolecular force ,Ab initio ,General Physics and Astronomy ,Infrared spectroscopy ,Trimer ,010402 general chemistry ,01 natural sciences ,Acceptor ,0104 chemical sciences ,chemistry.chemical_compound ,Crystallography ,chemistry ,0103 physical sciences ,Physics::Atomic and Molecular Clusters ,Fermi resonance ,Physics::Chemical Physics ,Physical and Theoretical Chemistry - Abstract
The appearance of multiple bands in the N–H stretching region of the infrared spectra of the neutral methylamine dimer and trimer is a sign of NH bend–stretch anharmonic coupling. Ab initio anharmonic calculations were carried out in a step-wise manner to reveal the origin of various bands observed in the spectrum of the methylamine dimer. A seven-dimensional potential energy surface involving symmetric and asymmetric stretching and bending vibrations of both the hydrogen bond donor and the acceptor along intermolecular-translational modes was constructed using the discrete variable representation approach. The resulting spectrum of the dimer shows five bands that can be attributed to the symmetric stretching (νsymD), asymmetric stretchin (νasymD), and bending overtone (2νbendD) of the donor moiety. These appear along with the combination band arising out of bending vibrations of the donor and acceptor (νbendD + νbendA) and with the combination of the intermolecular translational mode over the donor bending overtone (νtrans + 2νbendD). The spectrum of the trimer essentially consists of all the features seen in the dimer with marginal changes in band positions. The analysis of the experimental spectra based on the two-state deperturbation model and ab initio anharmonic calculations yield a matrix element of about 40 cm−1 for the N–H bend–stretch Fermi resonance coupling. In general, the IR spectra of the hydrogen-bonded amino group depict three sets of bands that arise due to bend–stretch Fermi resonance coupling.
- Published
- 2020
144. Anharmonic coupling behind vibrational spectra of solvated ammonium: lighting up overtone states by Fermi resonance through tuning solvation environments
- Author
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Chih-Kai Lin, Jer-Lai Kuo, and Qian-Rui Huang
- Subjects
Physics ,Quantitative Biology::Biomolecules ,Overtone ,Anharmonicity ,Solvation ,Ab initio ,General Physics and Astronomy ,Resonance ,Molecular physics ,Fermi resonance ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Spectroscopy ,Rotational–vibrational coupling - Abstract
Studies on the vibrational spectra of various ammonium-centered clusters under different solvation environments have raised interest over the last thirty years. The gas-phase infrared photodissociation spectroscopy (IRPD) experiments showed that these NH4+⋯Xn clusters exhibit rich spectral features from 2600 to 3400 cm−1. In this work, we have simulated the vibrational spectra and analyzed couplings among vibrational quantum states in the aforementioned frequency range using ab initio anharmonic algorithms. Originating from the anharmonic couplings between NH stretching fundamentals and bending overtones, Fermi resonance (FR) is a common feature in these spectra, and its extent is determined by the magnitude of couplings and the energy matching conditions between relevant states, which are governed by the proton affinity, number, and bonding configuration of the solvation species. For weakly bound clusters consisting of rare gas atoms, FR is insignificant but not negligible; for strongly bound clusters, such as ammonium–water clusters, the hydrogen-bonded NH stretching fundamentals redshift and reach a better resonance condition, and thus light up the bending overtones as prominent FR bands. Our simulated spectra are in good agreement with previous experimental reports of these ammonium-centered clusters and provide a better understanding of the vibrational coupling behind the spectra of the NH stretching region.
- Published
- 2020
145. Strong Fermi Resonance Associated with Proton Motions Revealed by Vibrational Spectra of Asymmetric Proton-Bound Dimers
- Author
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Asuka Fujii, Chen Wei Tsai, Chih-Kai Lin, Jake A. Tan, Jer-Lai Kuo, Ryunosuke Shishido, and Qian-Rui Huang
- Subjects
Physics ,Proton ,Hydrogen bond ,Overtone ,Infrared spectroscopy ,Protonation ,General Medicine ,General Chemistry ,Molecular physics ,Catalysis ,Ab initio quantum chemistry methods ,Proton affinity ,Fermi resonance ,Nuclear Experiment - Abstract
Infrared spectra for a series of asymmetric proton-bound dimers with protonated trimethylamine (TMA-H+ ) as the proton donor were recorded and analyzed. The frequency of the N-H+ stretching mode is expected to red shift as the proton affinity of proton acceptors increases. The observed band, however, shows a peculiar splitting of approximately 300 cm-1 with the intensity shifting pattern resembling a two-level system. Theoretical investigation reveals that the observed band splitting and its extraordinarily large gap of around 300 cm-1 is a result of strong coupling between the fundamental of the proton stretching mode and overtone states of the two proton bending modes, that is commonly known as Fermi resonance (FR). We also provide a general theoretical model to link the strong FR coupling to the quasi-two-level system. Since the model does not depend on the molecular specification of TMA-H+ , the strong coupling we observed is an intrinsic property associated with proton motions.
- Published
- 2020
146. Two-dimensional IR spectroscopy reveals a hidden Fermi resonance band in the azido stretch spectrum of β-azidoalanine
- Author
-
Saptarsi Mondal, Kyungwon Kwak, Hogyu Han, Hyeok Jun Kwon, Minhaeng Cho, and Junyoung Park
- Subjects
Azides ,Materials science ,Infrared ,Static Electricity ,Molecular Conformation ,General Physics and Astronomy ,Infrared spectroscopy ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Molecular physics ,Vibration ,Spectral line ,chemistry.chemical_compound ,Spectroscopy, Fourier Transform Infrared ,Molecule ,Physical and Theoretical Chemistry ,Spectroscopy ,Conformational isomerism ,Astrophysics::Galaxy Astrophysics ,Alanine ,Nitrogen Isotopes ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,chemistry ,Models, Chemical ,Isotope Labeling ,Fermi resonance ,Azide ,0210 nano-technology - Abstract
Azido stretch modes in a variety of azido-derivatized nonnatural amino acids and nucleotides have been used as a site-specific infrared (IR) probe for monitoring changes in their conformations and local electrostatic environments. The vibrational bands of azide probes are often accompanied by complex line shapes with shoulder peaks, which may arise either from incomplete background subtraction, Fermi resonance, or multiple conformers. The isotope substitution in the infrared probe has thus been introduced to remove Fermi resonances without causing a significant perturbation to the structure. Here, we synthesized and labeled the mid-N atoms of aliphatic azide derivatives with 15N to study the effects of isotope labelling on their vibrational properties. The FT-IR spectra of the aliphatic azide with asymmetric lineshape became a single symmetric band upon isotope substitution, which might be an indication of the removal of the hidden Fermi resonance from the system. We also noticed that the 2D-IR spectrum of unlabeled aliphatic azide has cross-peaks, even though it is not apparently identifiable. The 1D slice spectra obtained from the 2D-IR spectra reveal the existence of a hidden Fermi resonance peak. Furthermore, we show that this weak Fermi resonance does not produce discernible oscillatory beating patterns in the IR pump-probe spectrum, which has been used as evidence of the Fermi resonance. Therefore, we confirm that isotope labelling combined with 2D-IR spectroscopy is the most efficient and incisive way to identify the origin of small shoulder peaks in the linear and nonlinear vibrational spectra of various IR probe molecules.
- Published
- 2020
147. VIBRATIONAL SPECTRA OF H3O+...Xn: INTERPLAY BETWEEN FERMI RESONANCE AND COMBINATION BAND
- Author
-
Asuka Fujii, Qian-Rui Huang, and Jer-Lai Kuo
- Subjects
Physics ,Fermi resonance ,Atomic physics ,Vibrational spectra - Published
- 2020
- Full Text
- View/download PDF
148. Strained hydrogen bonding in imidazole trimer: a combined infrared, Raman, and theory study
- Author
-
Marco Eckhoff, Julia Zischang, Ricardo A. Mata, Thomas Forsting, Benjamin Schröder, and Martin A. Suhm
- Subjects
Materials science ,Hydrogen bond ,Anharmonicity ,General Physics and Astronomy ,Trimer ,02 engineering and technology ,Electronic structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,Hot band ,0104 chemical sciences ,symbols.namesake ,Physics::Atomic and Molecular Clusters ,symbols ,Molecule ,Fermi resonance ,Physical and Theoretical Chemistry ,0210 nano-technology ,Raman spectroscopy - Abstract
In this work, a careful analysis of anharmonic couplings in NH and some CH stretch modes of imidazole is carried out. This includes IR and Raman spectra of the isolated molecule and aggregates up to the trimer, together with two different theoretical approaches to the calculation of anharmonic shifts and absolute band positions. The imidazole dimer is vibrationally characterized for the first time in vacuum isolation under supersonic jet conditions, showing substantial shifts from previous helium droplet experiments and evidence for Fermi resonance for the hydrogen-bonded NH stretch. The most stable imidazole trimer structure is unambiguously shown to be cyclic with three non-equivalent, highly strained hydrogen bonds. This contrasts the helium droplet observation of a chain trimer involving two unstrained hydrogen bonds. These experimental conclusions are strongly corroborated by theory, including vibrational perturbation theory and anharmonic normal mode analysis. Systematic error compensation in some of these methods is emphasized. Intramolecular anharmonic coupling constants from perturbation theory are validated by Raman hot band jet spectroscopy of the monomer. Imidazole aggregation is shown to provide valuable benchmarking opportunities for electronic structure and in particular for anharmonic vibrational methods, covering the field of strong and strongly distorted hydrogen bonding.
- Published
- 2019
- Full Text
- View/download PDF
149. Manifestation of Fermi resonance in Raman spectra of micellar aqueous solutions of sodium octanoate
- Author
-
Sergey A. Burikov, Tatiana A. Dolenko, Ivan V. Plastinin, and Sergey Dolenko
- Subjects
Valence (chemistry) ,Aqueous solution ,Materials science ,Hydrogen bond ,Overtone ,Analytical chemistry ,Micelle ,Condensed Matter::Soft Condensed Matter ,symbols.namesake ,Micellar solutions ,Physics::Atomic and Molecular Clusters ,symbols ,Fermi resonance ,Physics::Chemical Physics ,Raman spectroscopy - Abstract
The paper presents the results of an experimental study of the role of the Fermi resonance (FR) between the overtone of the bending and symmetric valence vibrations of the water molecule in micellar solutions of sodium octanoate in the mechanisms of formation of the water valence band. The analysis of broad spectral bands was carried out using genetic algorithms and gradient methods. The frequency detuning between the components of the Fermidoublet for all the samples were obtained at room temperature. For aqueous solutions of sodium octanoate in the critical concentration of micelle formation (0.4 M) frequency detuning ceases to decrease with the growth of surfactant concentration, which is explained by the strengthening of the network of hydrogen bonds in the solution in the process of combining monomers and dimers of surfactants in multimolecular aggregates - micelles. A significant contribution of the Fermi resonance to the intensity of the valence band of water in sodium octanoate solutions was demonstrated. The FR interaction constants were calculated.
- Published
- 2020
- Full Text
- View/download PDF
150. The vibrational auto-adjusting perturbation theory
- Author
-
Emili Besalú, Eduard Matito, J. M. Barroso, Ove Christiansen, Josep M. Luis, and Ministerio de Educación y Ciencia (Espanya)
- Subjects
Chemistry ,Anharmonicity ,Overtone band ,Square matrix ,Vibrational partition function ,Quantum mechanics ,Excited state ,Vibrational energy relaxation ,Physics::Atomic and Molecular Clusters ,Perturbation (Quantum dynamics) ,Fermi resonance ,Química quàntica ,Physical and Theoretical Chemistry ,Perturbation theory ,Physics::Chemical Physics ,Quantum chemistry ,Pertorbació (Dinàmica quàntica) - Abstract
In this work a new method to calculate anharmonic vibrational ground and excited state energies is proposed. The method relies on the auto-adjusting perturbation theory (APT) which has been successfully used to diagonalize square matrices. We use as zeroth order correction the self-consistent vibrational energies, and with the APT approach we calculate the vibrational anharmonic correlation correction to any desired order. In this paper we present the methodology and apply it to a model system and formaldehyde. Vibrational APT approach shows a robust convergent behavior even for the states where the standard (Rayleigh-Schr¨odinger) vibrational Møller-Plesset perturbation theory is clearly divergent E.B. and J.M.B. thank the project CTQ2006-04410/BQU of the Spanish Ministerio de Ciencia y Tecnología. O.C. acknowledges support from the Danish Center for Scientific Computing (DCSC), the Danish national research foundation, the Lundbeck Foundation, and EUROHORCs for a EURYI award. J.M.L thanks the project CTQ2008-06696/BQU of the Spanish Ministerio de Ciencia y Tecnología
- Published
- 2020
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