Showing papers on "Fermi resonance published in 2004"
TL;DR: In this article, the structure of borohydrides MBH4 and their deuterides has been investigated by X-ray and neutron powder diffraction (M = K, Rb, Cs) and by infrared and Raman spectroscopy (M. = Na, K, rb, cb, N. Cs), and the properties of the overtones and combination bands, the Fermi resonance type interactions and the 10 Bt o 11 B splitting due to the presence of natural boron in the samples.
178 citations
TL;DR: In this article, a femtosecond pump-probe and Fourier transform infrared spectroscopy was applied to compare the spectral response of the amide I band and the NH-stretching band of acetanilide (ACN) and $N$-methylacetamide (NMA), as well as their deuterated derivatives.
Abstract: Femtosecond pump-probe and Fourier transform infrared spectroscopy is applied to compare the spectral response of the amide I band and the NH-stretching band of acetanilide (ACN) and $N$-methylacetamide (NMA), as well as their deuterated derivatives. Both molecules form hydrogen-bonded molecular crystals that are regarded to be model systems for polypeptides and proteins. The amide I bands of both ACN and NMA show a temperature-dependent sideband, while the NH bands are accompanied by a sequence of equidistantly spaced satellite peaks. These spectral anomalies are interpreted as a signature of vibrational self-trapping. Two different types of states can be identified in both crystals in the pump-probe signal: a delocalized free-exciton state and a set of localized self-trapped states. The phonons that mediate self-trapping in ACN and deuterated ACN are identified by their temperature dependence, confirming our previous results. The study shows that the substructure of the NH band in NMA (amide $A$ and amide $B$ bands) originates, at least partly, from vibrational self-trapping and not, as often assumed, from a Fermi resonance.
61 citations
TL;DR: In this paper, the band shape of hydrogen bond vibrations is studied theoretically, taking into account Fermi-Davydov resonance phenomena and strong interaction of the H-bond vibrations with the lattice phonons.
61 citations
TL;DR: In this paper, a theoretical simulation of the ν s stretching band of polycrystalline benzoic acid and its deuterated derivatives at 300 K is presented. But the simulation is restricted to the case where the high-frequency O−H(D) stretching and the low-frequency intermolecular O⋯O(O) stretching modes are taken into account.
51 citations
TL;DR: The extensive intermolecular hydrogen bonding in the crystal was identified by the shifting of bands due to the stretching and bending modes of the various functional groups.
44 citations
TL;DR: It is observed that the asymmetric stretch vibrational mode of the CO(2) molecule is red-shifted from the frequency of free CO2, with the red-shift increasing toward the lighter halide ions.
Abstract: Ion–molecule clusters of the heavier halide anions X−⋅CO2 (X=Cl−,Br−,I−) with CO2 have been studied by gas phase infrared photodissociation spectroscopy, using Ar evaporation from the complexes X−⋅CO2⋅Ar upon infrared excitation. We observe that the asymmetric stretch vibrational mode of the CO2 molecule is red-shifted from the frequency of free CO2, with the red-shift increasing toward the lighter halide ions. A similar trend is repeated in the region of the Fermi resonance of the combination bands of the asymmetric stretch vibration with two quanta of the bending vibration and the symmetric stretch vibration. We discuss our findings in the framework of ab initio and density functional theory calculations.
42 citations
TL;DR: In this article, a Fermi resonance analysis of gas-phase glycolaldehyde and small particles was carried out and the results showed that the results were in good agreement with the formation of long chains of monomeric glycolalde.
Abstract: The infrared spectra of gas-phase glycolaldehyde and small glycolaldehyde particles both exhibit a split carbonyl band around 1730 cm1. Ab initio calculations show that this splitting can be traced back to a Fermi resonance involving the C=O-stretching band and the first overtone of the CC-stretching band. The analysis of this resonance leads to detailed information about the conformation of glycolaldehyde in the particles. The results can be summarized as follows. (i) In the particles, monomers with OCCO dihedral angles of 0° and CCOH dihedral angles around 50° are strongly preferred. (ii) The intramolecular hydrogen bond observed in the gas phase is partly replaced by intermolecular hydrogen bonds. (iii) The calculated infrared spectrum and the results from the Fermi resonance analysis are in good agreement with the formation of long chains of monomeric glycolaldehyde. This is in contrast to the solid bulk, which consists of chemically bound dimers. Key words: Fermi resonance, conformation, glycolalde...
33 citations
TL;DR: The experimental and theoretically predicted Raman spectra for the first few alkanes in the homologous series: methane, ethane, propane and butane are presented for the region 2700-3100 cm −1.
30 citations
TL;DR: In this article, a strong coupling model was proposed to explain most of the isotopic and temperature effects in the polarized IR spectra of 1-naphthylacetic and 2 naphthymethylacetic acid molecules.
25 citations
TL;DR: This work marks the first observation of Fermi resonance the 2nu1 O-H stretching overtone of gas phase HNO3 using Fourier-transform infrared spectroscopy, and previously unobserved bands were assigned and integrated intensities were obtained.
25 citations
TL;DR: In this article, the in situ IR spectra of H3PW12O40·nH2O (n = 0−6.2) in the range 4000−1100 cm-1 were measured, and that of planar H5O2+ was investigated.
Abstract: The in situ IR spectra of H3PW12O40·nH2O (n = 0−6.2) in the range 4000−1100 cm-1 were measured, and that of H3PW12O40·6H2O (i.e., [H5O2+]3[PW12O403-]) with planar H5O2+ was investigated. The spectrum showed a broad continuum below 3700 cm-1, with peaks at 3420, 2720, 2030, and 1640 cm-1, and was deconvoluted into five bands at 3420, 2720, 2030, 1780, and 1640 cm-1. These bands, except for 2030 cm-1, were shifted by the deuteration and are assigned to the vibration modes of the planar structure. The vibration modes of the simplified model H5O2+·4OW(OH)4(OH2) were calculated by the quantum chemical method with the B3LYP/6-31+G* level: The 3420 cm-1 band is assigned to the overlap of the ν(OwHw) of the ν7 mode with the A component of Fermi resonance among ν8 (ν(OwHw)), ν3 (δ(OwHw2)), and ν11 (γ(OwHw2)) with the same species, of which the first mode is broadened by the anharmonic coupling of OwHw and OaHw vibrations. The bands at 2720 and 1780 cm-1 are probably assigned to separated BC components of the Ferm...
TL;DR: In this paper, several new infrared absorption bands for 32S16O3 have been measured and analyzed and the unraveling of the complex pattern of these bands was facilitated by a systematic approach to the understanding of the various interactions.
TL;DR: The changes in the spectra of the acidic group in chabazite are studied by quantum chemical calculations and the matrix elements of the vibrational Hamiltonian were calculated within the discrete variable representation basis set.
Abstract: The changes in the spectra of the acidic group in chabazite are studied by quantum chemical calculations. The zeolite is modeled by two clusters consisting of eight tetrahedral atoms arranged in a ring and seven tetrahedral atoms coordinated around the zeolite OH group. The potential energy and dipole surfaces were constructed from the zeolite OH stretch, in-plane and out-of-plane bending coordinates, and the intermolecular stretch coordinate that corresponds to a movement of the water molecule as a whole. Both the anharmonicities of the potential energy and dipole were taken into account by calculation of the frequencies and intensities. The matrix elements of the vibrational Hamiltonian were calculated within the discrete variable representation basis set. We have assigned the experimentally observed frequencies at ;2900, ;2400, and ;1700 cm 21 to the strongly perturbed zeolite OH vibrations caused by the hydrogen bonding with the water molecule. The ABC triplet is a Fermi resonance of the zeolite OH stretch mode with the overtone of the in-plane bending ~the A band! and the overtone of the out-of-plane bending ~the C band! .I n theB band the stretch is also coupled with the second overtone of the out-of-plane bending. The frequencies at ;3700 and ;3550 cm 21 we have assigned to the OH stretch frequencies of a slightly perturbed water molecule.
TL;DR: In this paper, a combined reflection-absorption infrared spectroscopy (RAIRS) and theoretical study on methoxide adsorbed on clean Ru(0 0 1) enabled to interpret the C-H stretching region of the spectrum.
TL;DR: In this paper, the molecular structures of L-thyroxine (T4), 3,5,3 � -triiodo-L-thyronine(T3) and 3, 5, 3 � -diiodo -L-thyrone (T2) were investigated by means of vibrational spectroscopy and density functional theory calculations using the B3LYP hybrid functional and the SDD effective core potential basis set, suitable for heavy atoms.
Abstract: The molecular structures of L-thyroxine (T4), 3,5,3 � -triiodo-L-thyronine (T3) and 3,5-diiodo-L-thyronine (T2) were investigated by means of vibrational spectroscopy and density functional theory calculations using the B3LYP hybrid functional and the SDD effective core potential basis set, suitable for heavy atoms. The experimental data were obtained from FT-IR and Raman spectra of the thyroid hormones in the crystalline state. The combined experimental and theoretical approach allows a consistent assignment for most of the fundamental modes in the range between 100 and 1650 cm −1 . It was found that, in general, the modes are largely localized in the individual rings and in the linkage connecting both rings. Hence it was possible to identify bands that are dominated by the internal coordinates of the ether bridge and the C–I stretchings. These bands are considered to be sensitive spectral markers for monitoring conformational changes of the hormones after insertion into phospholipid bilayers. Copyright 2004 John Wiley & Sons, Ltd.
TL;DR: New ab initio calculations of the potential-energy surface and the dipole moment are presented and are used in variational ro-vibrational calculations to assign the spectral features and demonstrate extensive mode mixing between the bend and the H-atom stretch modes in BrHI- and BrDI- due to Fermi resonances.
Abstract: Gas phase vibrational spectra of BrHI− and BrDI− have been measured from 6 to 17 μm (590–1666 cm−1) using tunable infrared radiation from the free electron laser for infrared experiments in order to characterize the strong hydrogen bond in these species. BrHI−⋅Ar and BrDI−⋅Ar complexes were produced and mass selected, and the depletion of their signal due to vibrational predissociation was monitored as a function of photon energy. Additionally, BrHI− and BrDI− were dissociated into HBr (DBr) and I− via resonant infrared multiphoton dissociation. The spectra show numerous transitions, which had not been observed by previous matrix studies. New ab initio calculations of the potential-energy surface and the dipole moment are presented and are used in variational ro-vibrational calculations to assign the spectral features. These calculations highlight the importance of basis set in the simulation of heavy atoms such as iodine. Further, they demonstrate extensive mode mixing between the bend and the H-atom str...
TL;DR: The basis-set dependence of the Fermi hole is emphasized and the effect of canonical, localized and delocalized Kohn-Sham and Hartree-Fock basis sets is examined for selected atoms and molecules.
Abstract: A reinterpretation of the Boyd–Coulson [R. J. Boyd and C. A. Coulson, J. Phys. B 7, 1805 (1974)] definition of the Fermi hole is presented. Through this reinterpretation, which makes no reference to the hypothetical Hartree level, we are able to show the essentially identical character of the Boyd–Coulson definition with the one based on a conditional probability analysis. The basis-set dependence of the Fermi hole is emphasized and the effect of canonical, localized and delocalized Kohn–Sham and Hartree–Fock basis sets is examined for selected atoms and molecules.
TL;DR: In this article, the effect of Fermi resonance on the rate of stochastic transitions over potential barriers was investigated and it was shown that large amplitudes of oscillations along the reaction path may support transitions over reaction barriers in the underdamped regime.
Abstract: We consider here the effect of Fermi resonance on the rate of stochastic transitions over potential barriers. As a typical phenomenon for Fermi resonance we investigate the fading of the energy between the oscillations in different degrees of freedom. Due to this fading phenomenon we see from time to time rather large amplitudes of oscillations along the reaction path which may support transitions over reaction barriers in the underdamped regime. As as an application we study the influence of Fermi resonance on enzyme reactions. In particular we investigate the possible effect of Fermi resonance on the breaking of peptide bonds.
TL;DR: In this paper, high-resolution infrared and coherent anti-Stokes Raman spectroscopies were used to study the fundamental modes and several hot bands of 32 S 18 O 3.
TL;DR: In this paper, the rotational-vibrational state energies were calculated utilizing an effective Hamiltonian, taking into account the rotation contribution to the Fermi resonance energy, and the effect of thermodissociation on the number of bound states of the carbon dioxide molecule.
Abstract: Using the spectroscopic characteristic of the carbon dioxide molecule, direct calculations of the total internal and vibrational partition sums for the principal isotopologue 12C16O2 in the temperature range 400–10 000 K were carried out in steps of 200 K. The rotational–vibrational state energies were calculated utilizing an effective Hamiltonian, taking into account the rotational contribution to the Fermi resonance energy. The method of direct summation by conditions was employed, taking into account the effect of thermodissociation on the number of bound states of the molecule. It is demonstrated that, in order to accurately calculate the partition sum Q at high temperature, it is necessary to solve combined equations with regard to the partition sum Q as well as the energy of dissociation D T . The values of Q and D T calculated by means of an iterative process are compared with the results obtained using other calculations.
TL;DR: In this paper, the infrared active ν7 and ν5 fundamentals of disilane, coupled by an x,y Coriolis interaction, have been analyzed on a Fourier transform spectrum between 2120 and 2225 cm−1, at the Doppler limited spectral resolution.
Abstract: The infrared active ν7 and ν5 fundamentals of disilane, coupled by an x,y Coriolis interaction, have been analysed on a Fourier transform spectrum between 2120 and 2225 cm−1, at the Doppler limited spectral resolution. A Fermi resonance with 2ν 2 + ν9 affects the Δ K = 1 side of ν7, and both ν7 and ν5 show the effects of several additional localized perturbations. Line splittings in the ν5 transitions are not observed, showing that the torsional splitting in the ν5 excited state and in the vibrational ground state are almost equal. The intrinsic torsional splitting of ν7 is found to be smaller than in the ground vibrational state by 0.0085 cm−1. This splitting value and those found for the other two infrared active degenerate fundamentals, ν8 and ν9, follow the trend expected from our theoretical predictions. Exploratory numerical calculations show that the decrease of the torsional splittings, observed in the fundamental degenerate vibrational states of disilane, can actually be accounted for by the head...
TL;DR: In this paper, the rotational spectrum of NC4P was extended to a large number of vibrationally excited states lying between 450 and 750 cm−1, namely (v5v6v7v8v9)
Abstract: A fairly efficient method for the production of the unstable NC4P molecule has been found, based on copyrolysis of phosphorus trichloride and cyclopropyl cyanide. This allowed us to extend the study of the rotational spectrum of NC4P to a large number of vibrationally excited states lying between 450 and 750 cm−1, namely (v5v6v7v8v9) = (00100), (01000), (10000), (00020), (00101), (01001), (00110), and (01010). The strong Fermi resonance which couples the v5 = 1 and v8 = 2 states and the l-type resonances between the different sublevels of the bending states have been taken into account in the analysis of the spectra. The identification of new excited-state spectra was facilitated by CCSD(T) calculations with the cc-pVQZ basis, which provided accurate predictions for a variety of spectroscopic constants, including harmonic vibrational wavenumbers, vibration–rotation coupling constants and l-type doubling constants. Accurate theoretical predictions for the equilibrium structure and the electric dipole moment of NC4P are also presented.
15 Dec 2004
TL;DR: In this paper, the hydrogen sulfide absorption spectrum in the 8400 - 8900 cm-1 spectral region, recorded at Kitt Peak National Observatory with Fourier transform spectrometer has been assigned and modeled within the effective Hamiltonian approach.
Abstract: The hydrogen sulfide absorption spectrum in the 8400 - 8900 cm-1 spectral region, recorded at Kitt Peak National Observatory with Fourier transform spectrometer has been assigned and modeled within the effective Hamiltonian approach. Three hundred and fifty six precise energy levels were derived from the spectrum analysis for the (211), (112), (032), (131), and (230) states of the second decade. These levels were modeled using Watson-type rotational Hamiltonian with consideration strong Coriolis and weak Fermi resonance interactions. The RMS deviation of the fitting for the main H232S isotope species represented 0.006 cm-1 with 59 adjustable parameters. New evaluations of the vibrational energies Ev=8539.5617 cm-1 for the (131)-(000) band, Ev=8637.1601 cm-1 for the (032)-(000) band and Ev=8539.9253 cm-1 for the (230)-(000) band have been obtained. The line intensities were fitted with rms deviation of 15%. The results obtained are compared with recent study.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this paper, the contributions of the Fermi resonances to the observed rotational constants in a model that determines the vibrational-rotational constants, the fermi term and the mixing between interacting vibrational states, the cubic potential constant ( φ 997 ) that connects interacting levels through a Fermani resonance, and the inertial defects.
TL;DR: In this article, the spectra of NO + photofragment excitation (PHOFEX) were obtained by scanning the dissociation laser in the wavelength range of 278-328 nm.
Abstract: The spectra of N 2 O + ions in A 2 Σ + state have been investigated. Pure parent N 2 O + ions, in the X 2 Π 3/2,1/2 (000) state, were prepared by (3+1) multiphoton ionization of jet-cooled N 2 O molecules using a laser beam at 360.55 nm. By introducing another laser, the parent ions were excited to the predissociative A 2 Σ + state, and the fragment NO + was detected by a time-of-flight mass spectrometer. The NO + photofragment excitation (PHOFEX) spectra were recorded by scanning the dissociation laser in the wavelength range of 278—328 nm. The PHOFEX spectra could be attributed completely to the A 2 Σ + ←X 2 Π transition of N 2 O + , in which most vibronic bands were observed for the first time. By considering the Fermi resonance between the ν 1 and ν 2 modes, the spectra were assigned, and the spectral constants, such as vibrational frequencies, anharmonic constants, and Fermi interaction constant, were obtained with relatively high reliability and precision.
TL;DR: In this article, the authors considered these resonances as q1D-periodic orbit resonance and obtained the obtained Fermi velocity and the scattering time are 4.4×10 4 ǫm/s and 2.1×10 −11 Ãǫs, respectively.
Abstract: Magnetooptical measurements have been performed on β ″-(BEDT-TTF)(TCNQ) using the cavity perturbation techniques. β ″-(BEDT-TTF)(TCNQ) has very exotic Fermi surface (FS). Several harmonic resonances were observed at various angles. We consider these resonances as q1D-periodic orbit resonance. The obtained Fermi velocity and the scattering time are 4.4×10 4 m/s and 2.1×10 −11 s, respectively. When the magnetic field was rotated in the b * a -plane, the similar resonances are observed. According to these results, the FS topology of the system at low temperature is discussed.
TL;DR: In this article, the authors measured temperature-dependent infrared spectra of a partially occupied HIO 3 ·HIO 3 crystal at 14-300 K in the spectral range of stretching and bending vibrations.
TL;DR: In this article, the structure of borohydrides MBH4 and their deuterides has been investigated by X-ray and neutron powder diffraction (M = K, Rb, Cs) and by infrared and Raman spectroscopy (M. = Na, K, rb, cb, N. Cs), and the properties of the overtones and combination bands, the Fermi resonance type interactions and the 10 Bt o 11 B splitting due to the presence of natural boron in the samples.
Abstract: Alkali borohydrides MBH4 and their deuterides have been investigated by X-ray and neutron powder diffraction (M = K, Rb, Cs) and by infrared and Raman spectroscopy (M = Na, K, Rb, Cs). At room temperature the compounds crystallize with a cubic high temperature (HT) structure having Fm¯ 3m symmetry in which the [BH4] − complexes are disordered. At low temperature (LT) the potassium compound transforms into a tetragonal low temperature structure having P42/nmc symmetry in which the [BH4] − complexes are ordered such as in the isotypic sodium congener. The B–H distances within the complex as measured on the deuteride at 1.5 K are 1.205(3) A. Indications for a partial ordering in the rubidium and cesium compounds exist but are not sufficient for a full structural characterization. Infrared and Raman spectra at room temperature are fully assigned for both hydrides and deuterides, including the overtones and combination bands, the Fermi resonance type interactions and the 10 Bt o 11 B splitting due to the presence of natural boron in the samples.