Showing papers on "Fermi resonance published in 2001"
TL;DR: In this paper, a 2D and 3D anti-Stokes Raman spectroscopy was used to study the properties of vibrational energy relaxation in polyatomic liquids and solutions.
133 citations
TL;DR: In this article, the infrared spectra of H 2 16 O and H 2 18 O trapped in solid argon were recorded in the range 8000-15 cm−1 at Ar/H 2O molar ratios between 2000 and 20.
125 citations
TL;DR: In this article, the Raman and infrared spectra of gypsum to 21 GPa at 300 K were obtained, which is consistent with a pressure-induced phase transition in the sulfate group in the vicinity of 5-6 GPa.
Abstract: We present Raman and infrared spectra of gypsum to 21 GPa at 300 K. Our measurements encompass the internal modes of the (SO4)−4 group that lie between 400 and 1150 cm−1, hydroxyl-stretching vibrations between 3200 and 3600 cm−1, and a libration and bending vibrations of the molecular H2O group. All vibrations of the sulfate group have positive pressure shifts, while the hydroxyl-stretching and -bending vibrations have a mixture of positive and negative pressure shifts: the effect of pressure on the hydrogen bonding of the water molecule thus appears to be complex. Near 5 GPa, the two infrared-active bending vibrations of the water molecule coalesce, and the morphology of the hydroxyl-stretching region of the spectrum shifts dramatically. This behavior is consistent with a pressure-induced phase transition in gypsum in the vicinity of 5–6 GPa, which is observed to be reversible on decompression to zero pressure. The spectral observations are consistent with the onset of increased disorder in the position of the water molecule in gypsum: the sulfate vibrations are largely unaffected by this transition. The Raman-active symmetric stretch of the sulfate group undergoes an apparent splitting near 4 GPa, which is interpreted to be produced by Fermi resonance with an overtone of the symmetric bending vibration. The average mode Gruneisen parameter of the 20 vibrational modes we sample is less than 0.05, in contrast to the bulk thermal Gruneisen parameter of 1.20. Accordingly, the vibrations of both water and sulfate units within gypsum are highly insensitive to volumetric compaction. Therefore, in spite of the changes in the bonding of the water unit near 5 GPa, metastably compressed gypsum maintains strongly bound molecular-like units to over 20 GPa at 300 K.
74 citations
TL;DR: Improvement of resolution of a gas phase hemispherical electron spectrometer permitted separate measurements of the excitation of each member of the well known Fermi dyad in CO2 by impact of slow electrons.
Abstract: Improvement of resolution of a gas phase hemispherical electron spectrometer (to 7meV FWHM) permitted separate measurements of the excitation of each member of the well known Fermi dyad in CO{sub 2} by impact of slow electrons. Absolute differential cross sections at a scattering angle of 135{sup o} were measured as a function of electron energy. The excitation was found to be highly selective both via the {Pi}{sub u}{sup 2} shape resonance around 3.6eV and via the virtual CO{sub 2}{sup -} state at low energy. The selectivity is surprising because both vibrational states ensuing from the Fermi resonance involve the same type of nuclear motion (bending and stretch) and excitation of both is symmetry allowed.
60 citations
TL;DR: In this article, the infrared spectra of six isotopic species of methanol trapped in solid nitrogen and argon were measured in the domain 7300-300 cm−1.
58 citations
TL;DR: There is extensive hydrogen bonding in the system in all three crystallographic directions and this is responsible for the changes in the position and intensity of several bands.
38 citations
TL;DR: In this article, it was shown that the Fermi resonance interaction between the SiOH bending fundamental and a doubly excited vibration gives rise to a mixed-state doublet around 800 cm−1.
Abstract: The band at about 4550 cm−1 in the near-infrared (IR) spectra of OH-containing high-surface area silicas is known to resolve into a doublet under certain experimental conditions. The interpretation of this by Tsyganenko [Zh. Fiz. Khim. (Moscow) 56 (1982) 2330], which has received no recognition so far, is advocated and is elaborated as follows: (1) there is Fermi resonance interaction between the SiOH bending fundamental and a doubly excited vibration giving rise to a mixed-state doublet around 800 cm−1, (2) the Fermi doublet propagates in the near IR in combinations with the OH stretching vibration (≈3750 cm−1). From a review of available IR transmission, inelastic neutron scattering (INS), and Raman scattering experimental data and model densities of vibrational states it is inferred that the doubly excited state causing Fermi resonance is likely to be either the first overtone of the bridging-oxygen rocking mode (400 cm−1 in the density of vibrational states) or the binary summation of the bridging-oxygen symmetric stretching in bent Si–O–SiOH units (the D1 Raman band near 490 cm−1, in the interpretation of Mulder et al.) with the A′ component of the Si–OH wagging mode (expected at about 300 cm−1). In the near-IR spectra of OH-containing vitreous silica and natural opals, the irregular shape of the band near 4500 cm−1, as argued, has a similar origin.
33 citations
TL;DR: In this paper, high-resolution (0.001 cm−1) coherent anti-Stokes Raman scattering (CARS) was used to observe the Q-branch structure of the IR-inactive ν1 symmetric stretching mode of 32S16O3 and its various 18O isotopomers.
28 citations
TL;DR: In this paper, the Fermi resonance system (0,1,0,0)/(0, 0,0-0,3) has been analyzed for the HCC13CN and H13CCCN isotopomers for the first time.
Abstract: The pure rotational spectra of the astrophysically important
monosubstituted HC3N-isotopomers HCC13CN, HC13CCN,
H13CCCN and HCCC15N in their ground and various vibrationally
excited states, which will be denoted (4, 5, 6, 7)
hereafter, have been studied extensively in the 2 mm region. Transitions of
the ground vibrational states and vibrational satellites appendant to the
two lowest bending fundamentals 6 and 7
have been measured up to 625 GHz. The Fermi resonance system (0,1,0,0)/(0,0,0,3)
has been analyzed for the HCC13CN and H13CCCN isotopomers
for the first time. Furthermore, pure rotational transitions of the four doubly
substituted isotopomers HC13C13CN, H13CC13CN,
H13C13CCN and HCC13C15N could
be detected for the first time, not only in the ground but also in vibrationally
excited states. This work is to provide accurate the astronomical community.
27 citations
TL;DR: In this paper, the CH-stretching overtone spectra of the methyl group in gaseous toluene C6D5CH3 were analyzed with a theoretical model which takes into account, within the adiabatic approximation, the coupling of the anharmonic CH stretch vibrations, described by Morse potentials, with the quasifree internal rotation and with isoenergetic combination states involving the six angle deformation modes.
Abstract: The CH-stretching overtone spectra of the methyl group in gaseous toluene C6D5CH3 are recorded with conventional Fourier transform near infrared spectroscopy in the ΔvCH=1–4 regions and by intracavity laser photoacoustic spectroscopy in the ΔvCH=5 and 6 regions. All spectra exhibit a complex structure. They are analyzed with a theoretical model which takes into account, within the adiabatic approximation, the coupling of the anharmonic CH stretch vibrations, described by Morse potentials, with the quasifree internal rotation of the methyl group and with isoenergetic combination states involving the six angle deformation modes of the methyl group. Using uniquely determined canonical potential-energy and kinetic-energy matrices allows us to solve the problem of indeterminacy caused by the description of molecular vibrations in such redundant coordinates. A set of Fermi resonance parameters and their variation with the internal rotation coordinate are determined from the fitting of the ΔvCH=1–6 overtone spec...
25 citations
TL;DR: The ground state vibrational energy levels of jet-cooled SiCH and SiCD have been studied by a combination of laser-induced fluorescence and wavelength-resolved fluorescence techniques.
Abstract: The ground state vibrational energy levels of jet-cooled SiCH and SiCD have been studied by a combination of laser-induced fluorescence and wavelength-resolved fluorescence techniques. The radicals were produced by a pulsed electric discharge at the exit of a supersonic expansion using tetramethylsilane or methyltrichlorosilane as the precursor. Emission spectra have been obtained by pumping both perpendicular and parallel (vibronically induced) bands, providing complementary information on the Si–C stretching and Si–C–H bending modes. Ground state energy levels up to 4000 cm−1 have been assigned and fitted using a vibrational Hamiltonian that incorporates Renner–Teller, spin–orbit, vibrational anharmonicity, and Fermi resonance interactions. The validity of the derived parameters has been tested using the isotope relations.
TL;DR: Mode coupling in a protein molecule was studied by a molecular dynamics simulation of the intramolecular vibrational energy transfer in myoglobin at near zero temperature and it was found that the vibrationalenergy is transferred from a given normal mode to a very few number of selective normal modes.
Abstract: Mode coupling in a protein molecule was studied by a molecular dynamics simulation of the intramolecular vibrational energy transfer in myoglobin at near zero temperature. It was found that the vibrational energy is transferred from a given normal mode to a very few number of selective normal modes. These modes are selected by the relation between their frequencies, like Fermi resonance, governed by the third order mode coupling term. It was also confirmed that the coupling coefficients had high correlation with how much the coupled modes geometrically overlapped with each other.
Journal Article•
TL;DR: In this article, the authors showed that the νC=O frequency of 2-cyclohexene-1-one occurs at a lower frequency than the observed νc=O mode of cyclohexanone, possibly caused by expanded conjugation effects.
Abstract: The carbonyl stretching vibration, νC=O of 2-cyclohexene-1-one, is in Fermi resonance with a combination tone. The amount of Fermi resonance interaction between these two modes is dependent upon the amount of solute/ solvent interaction due to hydrogen bonding between the carbonyl oxygen and the solvent proton. The corrected νC=O frequency of 2-cyclohexene-1-one occurs at a lower frequency than the observed νC=O mode of cyclohexanone, possibly caused by expanded conjugation effects. The carbonyl stretching modes of cyclic ketones were also affected by interaction with the ROH/CCl 4 mixed solvent system.
TL;DR: In this article, the lowest frequency parallel fundamental band ν5 of CH3SiH3 near 700 cm−1 was measured at a resolution of 0.004 µm with Fourier transform spectroscopy to investigate vibration-torsion-rotation interactions in symmetric top.
Abstract: The lowest frequency parallel fundamental band ν5 of CH3SiH3 near 700 cm−1 has been measured at a resolution of 0.004 cm−1 with Fourier transform spectroscopy to investigate vibration–torsion–rotation interactions in symmetric tops. The torsional splittings in the spectrum are increased from ∼0.005 cm−1 to ∼1 cm−1 by Fermi-type vibration–torsion interactions between the torsional stack (v6=0,1,2,…) in the ground vibrational state and the corresponding stack for v5=1. Resonant interactions were observed between the states (v5=1,v6=0) and (v5=0,v6=5) for the rotational series with (k=±1,σ=∓1), where σ labels the torsional sublevels. In this resonance, the two unperturbed states are near opposite limits for torsional motion: (v5=0,v6=5) involves nearly free rotation, while (v5=1,v6=0) involves small amplitude torsional oscillation. For the (k=±1,σ=∓1) rotational series, perturbation-allowed transitions in the high overtone (v6=5←0) were observed. Over 750 frequencies measured here have been analyzed together...
TL;DR: In this article, an ab initio quartic force field calculated from a cc-pVTZ basis set at CCSD(T) level of theory is used to compute the vibrational energy levels of diphosphorus oxide, P 2 O, in the range 200-2000 cm −1.
TL;DR: The concentration dependence of the shape of absorption bands in the spectrum of CF4 in liquid argon is studied in the concentration range (0.01-17)×10−3 molar fractions at 93 K in this article.
Abstract: The concentration dependence of the shape of absorption bands in the spectrum of CF4 in liquid argon is studied in the concentration range (0.01–17)×10−3 molar fractions at 93 K. In all spectral regions related to ν3, the shape of the spectral function is determined, along with the Fermi resonance 〈νi,ν3+1,ν4|≈〈νi,ν3,ν 4+2|, by the resonance dipole-dipole interaction. In the spectral region of the Fermi doublet ν 1+ν3≈ ν1+2ν4, the spectrum of the contact (CF4)2 dimer is identified. Agreement between this spectrum and the calculated spectrum is achieved by simultaneously taking intramolecular and intermolecular resonances into account. The distance R
C-C in the dimer is 4.85(15) A. The calculations of the spectra of (12CF4)2 and (13CF4−12CF4) dimers with this value of R
C-C in the region ν 3≈2ν4 agree with the experiment.
TL;DR: In this article, the attenuated total reflection FTIR difference spectroscopy was used to measure the effect of Fermi resonance (ν1======+ 2ν2) on the water bands.
Abstract: Saturated solutions of LiCl, NaCl, KCl, NH4Cl, NH4Br, NH4I, CaCl2 and MgCl2
against pure water are recorded using attenuated total reflection FTIR difference spectroscopy. All ions show distinct effects on the water bands which result in several positive and negative bands. For the anions, band shifts to higher frequencies are found in the sequence F−, Cl−, Br−, I−. An opposite shift is observed for the cations in the sequence NH4+, K+, Na+, Li+. With the shift of the band envelope to lower wavenumbers, bands are visible which are due to the effect of Fermi resonance (ν1
+ 2ν2). Quantum-mechanical calculations using the GAUSSIAN 94 program package with the 6311G +
+ (3df,3pd) basis set were performed for the ions and one water molecule. Bands were calculated for water–ion formations in C2v and Cs symmetry. The observed and calculated frequency shifts correspond to changes in the geometry and charge separation of the
water molecules opposing the ion.
TL;DR: In this article, a reduced three-dimensional Hamiltonian model in terms of internal coordinates was employed to study the Si-H stretching and bending vibrations including 5ν1 and 6ν1 which were recently recorded using optoacoustic spectroscopy.
Abstract: Fourier transform overtone spectra of SiHF3 were recorded in the region of 2500–9000 cm−1 and vibrationally assigned. Experimental intensities were estimated. The 3ν1 overtone band at 6753 cm−1 was observed to be more than 10 times weaker than the 4ν1 band. A reduced three-dimensional Hamiltonian model in terms of internal coordinates was employed to study the Si–H stretching and bending vibrations including 5ν1 and 6ν1 which were recently recorded using optoacoustic spectroscopy. Potential energy parameters were optimized by fitting to experimental band centers. The Fermi resonance between the Si–H stretching and bending motions was found to be insignificant. Band intensities were computed using ab initio one- and three-dimensional dipole moment surfaces (DMS) expanded to polynomials in terms of symmetrized internal coordinates. The intensity anomaly of 3ν1 is understood as resulting from cancellation of contributions by the linear and quadratic terms in the DMS expansion. The behavior of X–H stretching ...
TL;DR: The Fermi resonance coupling between the v2 and 2v7 vibrations of EC have been analysed using a standard perturbation model and provided information regarding the molecular structure of these solutions, and the fact that the structure is also concentration dependent.
TL;DR: In this paper, the disappearance of the LO Raman anomaly as well as the pronounced broadening of the TO mode with pressure are explained in terms of pressure-dependent third-order anharmonic interactions with two-phonon states.
Abstract: with pressure and develops into a narrow LO phonon peak near 4 GPa. The disappearance of the LO Raman anomaly as well as the pronounced broadening of the TO mode with pressure are explained in terms of pressure-dependent third-order anharmonic interactions with two-phonon states. A Fermi resonance model, which is based on a shell model fit of available phonon dispersion data, fully accounts for the changes in Raman line shapes under pressure. Low-temperature Raman spectra of the tetragonal CuBr-IV and cubic CuBr-V high-pressure phases are also reported. An assignment of the observed Raman modes of these phases is proposed.
TL;DR: In this article, the vibrational frequencies and potential energy distribution of ortho, meta and para nitraminopyridine N -oxides are compared with the structures obtained using semi-empirical AM1, PM3 and MNDO calculations.
TL;DR: In this article, an internal coordinate force field model was used to study the Si−H stretching and bending polyad of the SiHD3 molecule. And the potential parameters were optimized by fitting to the experimental band centers, which indicated a slow redistribution of vibrational energy between these two degrees of freedom.
Abstract: Overtones of the Si−H stretching−bending polyad of the SiHD3 molecule are studied using an internal coordinate force field model. The potential parameters are optimized by fitting to the experimental band centers. The Fermi resonance between the Si−H stretching and bending motions is insignificant due to cancellation of the contributions from kinetic and potential terms. This suggests a slow redistribution of vibrational energy between these two degrees of freedom and induces local mode character of respective vibrations. Band intensities are calculated by using ab initio one- and three-dimensional dipole moment surfaces (DMS). These agree reasonably well with the observations. The successful reproduction of relative intensities between the (n1 − 1)v1 + 2v5 stretching−bending combination bands and the n1v1 stretching bands establishes the importance of the bending motion in the multidimensional DMS for intensity investigations.
TL;DR: In this article, the vibrational energy levels of coupled stretching and bending overtone transitions in polyatomic molecules XH 3 and XH 4 were calculated using an algebraic method, in which couplings between bending and stretching are described by Fermi resonance terms.
01 Jan 2001
TL;DR: In this article, interpretive spectroscopy for infrared and Raman spectra is discussed and fundamental frequencies that are characteristics of groups of atoms (termed functional groups) with common group names and general infrared locations (in wavenumbers).
Abstract: This chapter discusses interpretive spectroscopy for infrared and Raman spectra. Fundamental frequencies that are characteristics of groups of atoms (termed functional groups) with common group names and general infrared locations (in wavenumbers) are also discussed. The chapter also discusses the fingerprint frequencies that occur because of interactions of the molecular vibrations of the entire molecule rather than specific functional groups. Because the infrared spectrum is unique to an individual molecule, it is termed the fingerprint of that molecule, much as the fingerprint of a person indicates the specific identity of that person. However, in identifying the unique “fingerprint vibrations” of a molecule, information is presented as to the approximate molecular formula and composition of the molecule. The chapter then discusses coupling of vibrations, which indicates that the oscillators, or molecular vibrations of two or more molecules, are interactive. Therefore, the original vibrational energy states (if the vibrations could occur independently of one another) result in split energy states due to the interaction of the vibrations. Coupling is divided into two basic orders, first and second (Fermi resonance). These are explained in the chapter.
TL;DR: In this article, the reduced Hamiltonian models in terms of normal and curvilinear internal coordinates are used to study the Fermi resonance between the SiH stretching and bending modes and analyse the observed band centres associated with the siH chromophore.
Abstract: The Fourier transform and Fourier transform intracavity laser absorption spectra of the gas phase SiHCl3 molecule were recorded from 1000 cm-1 up to 13 000 cm-1. The normal mode analysis is carried out to fit the observed band centres. The reduced Hamiltonian models in terms of normal and curvilinear internal coordinates are used to study the Fermi resonance between the SiH stretching and bending modes and analyse the observed band centres associated with the SiH chromophore. The resonance in the SiH chromophore is found not to be important due to the cancellation of the contributions from the kinetic and the potential coupling terms. Off-diagonal anharmonic constants between the SiH stretching and bending manifold and the molecular frame have been determined. The SiH chromophore vibrational intensities are also reported.
TL;DR: In this article, the temperature dependence of the metal-molecule stretch vibrational mode of CO chemisorbed on a Pt(111) surface using infrared spectroscopy was investigated.
Abstract: We present an experimental study of the temperature dependence of the metal-molecule stretch vibrational mode of CO chemisorbed on a Pt(111) surface using infrared spectroscopy. The previously reported doublet structure in the vicinity of the Pt–CO stretch for bridge bonded 12C16O, which we assigned to a Fermi resonance, exhibits a strong temperature dependence. The doublet vanishes at 50 K, reducing to one single peak with twice the intensity. This supports our previous interpretation and we are in this paper able to discuss this Fermi resonance in more detail. In addition, we have investigated how the Fourier transform infrared technique may influence the observed peak widths.
TL;DR: In this paper, the existence of strongly localized modes in thin films and crystals with Fermi resonance interaction between vibration modes of molecules is investigated theoretically in two-and three-dimensional systems.
Abstract: We report the existence of strongly localized modes in thin films and crystals with Fermi resonance interaction between vibration modes of molecules. Several families of bright and dark localized modes are investigated theoretically in two-and three-dimensional systems. Simple theoretical estimations are confirmed by numerical calculations. It is shown that in higher dimensions the solutions exist which do not have their one-dimensional analogs. The strongly localized Fermi resonance modes demonstrate the threshold behavior in any dimension in contrast to the nonlinear lattices with cubic interaction between sites.
TL;DR: With a tunable diode-laser spectrometer, absolute line intensity measurements have been made in the spectrum of cyanogen chloride in the vicinity of 710 cm(-1) and the influence of the Fermi resonance on the band intensity has been analyzed.
Posted Content•
TL;DR: In this article, the authors measured the line width of the E2g phonon of the superconductor MgB2 and NbB2 using the Fermi resonance.
Abstract: Phonon spectra have been investigated by micro-Raman scattering from 290 to 20K. New peaks at 500 and 674 cm-1 appear below 250K in MgB2. These peaks are explained by the Fermi resonance, where Raman-active E2g intereacts with the overtone of E1u due to anhamonicity. Raman spectra of the isostructural RB2 (R=Al, Mn, Nb and Ti) have been also measured at 290K. The line width of E2g phonon of the superconductor MgB2 and NbB2 shows the broader than that of the non-superconductors. It is found that the anharmonicity of phonons is important for the superconductivity for MgB2.