Vibrational spectra of crystalline H2SeO3 in the O-H stretching region

IR transmission, near-normal IR reflection and polarized Raman spectra of single crystals of selenious acid (H₂SeO₃) have been obtained at temperatures between 77°K and 335°K. The observed bands in the O-H stretching region have been assigned to two types of O-H….O bonds in the crystal structure. The spectral results appear to rule out correlation field splittings, intramolecular coupling, or Fermi resonance as explanations for the observed splitting. A proposed model based on intermolecular coupling of O-H….O vibrations to explain the splitting of the O-H stretching region is given.     

FT-IR Study of the Interaction Between H2O,D2O,HOD, and Pyridines

Abstract

The complexes between H₂O, D₂O, HOD and pyridine have been studied in 1,2-dichloroethane by FT-IR spectrometry. Equal splittings of the stretching bands of H₂O and D₂O about their uncoupled vibrations are observed. The coupling between the asymmetric and symmetric vibrations reaches a value of zero when the band separation is greater than 500 cm^?1 for the OH vibrations and 365 cm^?1 for the OD vibrations. The v_OH stretching frequencies of the HOD ‥ complexes and the v_OD stretching frequencies of the DOH‥ complexes increase by complex formation. These features are explained by an electronic reorganization within the hydrogen bond.     

Raman spectroscopic study of the uranyl carbonate mineral zellerite

Raman and infrared spectra of the uranyl mineral zellerite, Ca[(UO₂)(CO₃)₂(H₂O)₂]·3H₂O, were measured and tentatively interpreted. U O bond in uranyl and O H···O hydrogen bonds were calculated from the vibrational spectra. The presence of structurally nonequivalent water molecules in the crystal structure of zellerite was inferred. A proposed chemical formula of zellerite is supported. Raman bands at 3514, 3375 and 2945 cm⁻¹and broad infrared bands at 3513, 3396 and 3326 cm⁻¹ are related to the ν OH stretching vibrations of hydrogen‐bonded water molecules. Observed wavenumbers of these vibrations prove that in fact hydrogen bonds participate in the crystal structure of zellerite. The presence of two bands at 1618 and 1681 cm⁻¹ proves structurally distinct and nonequivalent water molecules in the crystal structure of zellerite. Copyright © 2008 John Wiley & Sons, Ltd.     

Structure of ZnZrF<Subscript>6</Subscript> · <Emphasis Type="Italic">n</Emphasis>H<Subscript>2</Subscript>O (<Emphasis Type="Italic">n</Emphasis> = 6–2) and ZnZrF<Subscript>6</Subscript> crystallohydrates according to vibrational spectroscopy data

Fluoridezirconate crystallohydrates ZnZrF₆ · nH₂O (n = 6–2) and anhydrous ZnZrF₆ are investigated by vibrational spectroscopy and thermography. The influence of the hydrate number on the structure of the cationic and anionic sublattices of the crystallohydrates is studied. The changes in the strength of HOH···F and HOH···O hydrogen bonds of coordinated and outer-sphere water molecules occurring with variations in the hydrate number are determined by changes in the IR spectra. The IR spectra of ZnZrF₆ · nH₂O (n =6, 4) compounds, which have isolated complex anions [ZrF₆]^2– in their structure, revealed a band with two peaks in the range of 3470–3430 cm^–1, which corresponds to stretching vibrations of coordinated water molecules. The spectra of ZnZrF₆ · nH₂O (n = 5, 3, 2, 1) crystallohydrates with a polymeric structure show a high-frequency shift of this band, which corresponds to weakening of hydrogen bonds. The vibrations of crystallization water molecules involved in the network of strong O–H···F and O–H···O hydrogen bonds manifest themselves in the spectra of ZnZrF₆ · nH₂O (n =5, 3) crystallohydrates by broad structureless bands in the region of stretching, bending, and libration vibrations.     

Local mode vibrations of water

Classical trajectory calculations on a realistic potential for the stretching vibrations of the water molecule are used to demonstrate the existence of stable local vibrational modes, which occur in degenerate pairs. The proportion of phase space occupied by such modes increases with increasing energy, with a clearly characterized (0, 2) local state in a local quantum number assignment. It is argued that quantum mechanical corrections will lead to a local mode splitting which is predicted to decrease in magnitude along any given stretching vibrational progression, and to be larger for a given quantum state of D₂O than for H₂O.     

A Raman spectroscopic study of bukovskýite Fe2(AsO4)(SO4)(OH)· 7H2O,a mineral phase with a significant role in arsenic migration

The Raman spectrum of bukovskýite [Fe³⁺₂(OH)(SO₄)(AsO₄)· 7H₂O] has been studied and compared with that of an amorphous gel containing specifically Fe, As and S, which is understood to be an intermediate product in the formation of bukovskýite. The observed bands are assigned to the stretching and bending vibrations of (SO₄)²⁻ and (AsO₄)³⁻ units, stretching and bending vibrations and vibrational modes of hydrogen‐bonded water molecules, stretching and bending vibrations of hydrogen‐bonded (OH)⁻ ions and Fe³⁺ (O,OH) units. The approximate range of O H···O hydrogen bond lengths was inferred from the Raman spectra. Raman spectra of crystalline bukovskýite and of the amorphous gel differ in that the bukovskýite spectrum is more complex, the observed bands are sharp and the degenerate bands of (SO₄)²⁻ and (AsO₄)³⁻ are split and more intense. Lower wavenumbers of δ H₂O bending vibrations in the spectrum of the amorphous gel may indicate the presence of weaker hydrogen bonds compared to those in bukovskýite. Copyright © 2011 John Wiley & Sons, Ltd.     

Benzene adsorption on nickel (100) and (111) faces studied by leed and high resolution electron energy loss spectroscopy

Studies of benzene (C₆H₆ and C₆D₆) adsorption have been performed by high resolution electron energy loss spectroscopy (HRELS) and LEED experiments on nickel (100) and (111) single crystal faces at room temperature. Chemisorption induces ordered structures, c(4 × 4) on Ni(100) and (2√3 × 2√3)R30° on Ni(111), and typical energy loss spectra with 4 loss peaks accurately identified with the strongest infrared vibration bands of the gazeous molecules. Benzene chemisorption preserves the aromatic character of the molecule and involves respectively 8 nickel surface atoms on the (100) face and 12 on the (111) face by adsorbed molecule. The interaction takes place via the π electrons of the ring. Significant shifts of the CHτ bending and CH stretching vibrations show a weakening of the CH bonds due to the formation of the chemisorption bond and a coupling of H atoms with the nickel substrate.     

Fourier Transform Vibrational Spectra of Magnesium Hydrogenphosphate Trihydrate. I. The O-H Stretching Region∗

Abstract

The Fourier transform (FT) infrared and Raman spectra of newberyite, MgHPH₄ - 3H₂O are studied in the region where the stretching vibrations of the water molecules (protiated and deuterated) and the O-H/O-D stretches of the hydrogenphosphate anions are expected to appear. The O-H stretching vibrations give rise to a complex feature known as the A,B,C trio. Since neither of the maxima found below 3000 cm^?1 represents a true band arising from a given fundamental, it is pointless to correlate their frequencies with the observed O…O distances. In the water stretching region, the two bands with highest frequencies undoubtedly correspond to the anti symmetric and symmetric stretch of one type of the water molecules. The stretching vibrations of one of the remaining two types of H₂O molecules are clearly uncoupled and the O-H oscillator involved in the weaker hydrogen bond is responsible for a band at 3376 cm^?1 whereas the rest of the water stretchings are apparently overlapped yielding the complex band below 3320 cm^?1. Thus the situation is again complicated and the correlations between the frequencies and the O_w…O distances are inappropriate. The two bands at highest frequencies (3522 and 3483 cm^?1 at RT) exhibit a positive temperature coefficient.

     

Interactions of D2O with CO and CO2 molecules at cryogenic temperatures

On the basis of the matrix effect of secondary-ion mass spectrometry (SIMS), the intermolecular interactions between D₂O and hydrophobic molecules have been investigated at temperature of 15 K. The D⁺ yield is found to be enhanced markedly relative to the D₃O⁺ yield when the D₂O molecule forms a complex with the CO or CO₂ molecules on the surface. The CO molecules are incorporated in the inner pores of amorphous solid water and then cover the outermost surface facing to the vacuum, which is followed by the 3D-island growth on it. A similar result is obtained for the adsorption of the CO₂ molecule but the filling of the inner pores is not complete due to the lower mobility of the CO₂ molecule. The D₂O film grows on the CO₂ layer, but a pure D₂O film is hardly formed on the CO layer due to the occurrence of intermixing.     

Switching of hydrogen bonds of water in ionic liquid, 1‐butyl‐3‐methylimidazolium tetrafluoroborate

We have investigated temperature‐induced Raman spectral changes of deuterated water in an ionic liquid, 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([bmim][BF₄]), between room temperature and 77 K. The comparison of the OH and OD stretching vibrational spectra at 77 K shows that the strength of the hydrogen bonds in [bmim][BF₄]–water mixtures strongly depends on the type of water, i.e. H₂O and D₂O. In the [bmim][BF₄]–D₂O system, remarkably strong hydrogen bonds form at low temperatures, but they switch to nearly free hydrogen bonds on heating. Copyright © 2013 John Wiley & Sons, Ltd.     

IR Spectra and dipole moment function of the H2S molecule in the gas and liquid phases

The IR spectra of H₂S molecules in the gas and liquid phases and in solutions of liquefied noble gases are experimentally studied over a wide range of frequencies, including the regions of second- and third-order transitions. Based on experimental data on the parameters of the effective dipole moment, the first, second, and third derivatives of the dipole moment of the H₂S molecule with respect to the normal coordinates are recovered. The values of the first derivatives with respect to the coordinates associated with the stretching vibration are abnormally small in comparison with the higher-order derivatives. The change in the dipole moment of the molecule H₂S under the influence of the intermolecular forces on gas-liquid transition is examined. The observed anomalously large (more than 200-fold) increase in the absolute intensity of the fundamental stretching vibration band ν_str cannot be accounted for by abnormally strong intermolecular interaction forces. The increase in the absolute intensity of the ν_str band is associated with abnormally small first derivatives of the dipole moment of the gas-phase molecule. The effect of the intermolecular forces on the dipole moment is compared to that for the H₂O molecule.     

Analysis of the interactions in FCCF:(H2O) and FCCF:(H2O)2 complexes through the study of their indirect spin–spin coupling constants

A theoretical study of FCCF:(H₂O)_n complexes, with n?=?1 and 2, has been carried out by means of ab initio computational methods. Three kinds of interactions are observed in the complexes: H···π and H···F hydrogen bonds and O···FC tetrel bonds. The indirect spin–spin coupling constants have been calculated at the CCSD/aug-cc-pVTZ-J computational level. Special attention has been paid to the dependence of the different intramolecular coupling constants in FCCF on the distance between the coupled nuclei and the presence or absence of water molecules. The exceptional sensitivity shown by these coupling constants to the presence of water molecules is quite notorious and can provide information on the bonding structure of the molecule.     

Die Eigenschwingungen des Metall-Hydratkomplexes in BeSO4·4H2O und BeSO4·4D2O

Infrared reflection spectra of single crystals of BeSO₄·4H₂O and BeSO₄·4D₂O have been obtained in polarized light at 300°K and at 14°K in the region between 4000 cm^?1 and 300 cm^?1. By a Kronig-Kramers analysis, the frequencies of the infrared active transitions have been calculated. These transitions are attributed to internal vibrations of the water molecules and sulfate ions and, in the region between 1000 cm^?1 and 300 cm^?1, especially to internal and external vibrations of the tetrahedral Be⁺⁺·4aqu-complexes. The vibrational modes of these complexes consist of a superposition of translational and librational modes of the water molecules and translational modes of the central Be⁺⁺-ion. The vibrational frequencies and normal modes of this complex have been calculated in a central-force model, and force-constants have been determined by fitting the calculated frequencies to the observed spectra. The calculations have shown that the modes, which comprise mainly translational motions of the water molecules, are strongly coupled with librational motions of the water molecules. On the other hand, there exist pure librational modes with practically no admixture of translational motions. The optimum sets of force constants for the BeSO₄·4H₂O crystal and the BeSO₄·4D₂O crystal differ in a manner which can be understood under the assumption that the dimensions of the Be(D₂O)₄ complex are about 0.1 Å larger than those of the Be(H₂O)₄ complex. Some arguments supporting this conclusion will be discussed.     

Ramsey terms for two-, three-, and four-bond coupling involving 15N and 17O in hydrogen-bonded and nonhydrogen-bonded systems: are coupling constants sensitive to RAHBs?

Ab initio EOM-CCSD/(qzp,qz2p) calculations have been performed on complexes with intermolecular hydrogen bonds involving ¹⁵N and ¹⁷O, and molecules with and without intramolecular hydrogen bonds involving these nuclei. Coupling constants across intermolecular hydrogen bonds are well approximated by the Fermi-contact (FC) term. In general, ^2hJ(X–Y) for intramolecular coupling across X–H^…Y hydrogen bonds are not sensitive to the presence of resonance-assisted hydrogen bonds (RAHBs). However, ^2hJ(O–O) for coupling across the intramolecular hydrogen bond in malonaldehyde is greater than ^2hJ(O–O) for its saturated counterpart, so that ^2hJ(O–O) is sensitive to the presence of the RAHB. This is also the case for the sulphur analogues of malonaldehyde. For these unsaturated hydrogen-bonded molecules, molecules with carboxyl groups, and trans-glyoxal, J is dominated by the paramagnetic spin orbit (PSO) term. For these systems, the primary mode of coupling transmission is through the conjugated chain. For complexes with intermolecular hydrogen bonds, saturated molecules with intramolecular hydrogen bonds, unsaturated and saturated molecules in which the hydrogen bond has been broken, and unsaturated molecules with intramolecular N–H^…N or O–H^…N hydrogen bonds, J is dominated by the FC term. FC domination in hydrogen-bonded systems indicates that the primary transmission mode is across the hydrogen bond.     

Infrared and Raman spectra of aquamolybdenum (VI) oxide hydrate (MoO3·2H2O)

The infrared and Raman spectra of MoO₃·2H₂O are recorded and analysed on the basis of vibrations due to MoO₆ octahedra and H₂O molecules. Considerable changes in the frequencies of the octahedra have been observed due to strong distortion in the octahedral arrangement. The inactivev ₆ vibration of O _h symmetry became active in the Raman spectrum. Co-ordinated (aquated) and hydrated (interlayer) water molecules give rise to different frequencies.     

Far-infrared absorption intensities of H2O and D2O in C6H6

Far-i.r. absorption intensities have been measured for H₂O and D₂O in C₆H₆ solutions. Beer's law plots were found to be nonlinear. From the plots, the equilibrium constants of dimer formation in benzene were estimated to be 2.4M^-1 and 3.3M^-1 for H₂O and D₂O at 20°C, respectively. Based on Onsager's reaction field and including explicitly the effect of differences in molecular size between solute and solvent molecules, the internal moment of a water molecule and the volume ratio of a molecule to a cavity were estimated from the integrated absorption intensity of a D₂O monomer in C₆H₆ as 1.98 D and 0.7, respectively     

A possible correlation between a Jahn-Teller coupling and a Raman scattering

It has been shown how the Raman line of a degenerate vibration can be caused by a vibronic coupling in a degenerate electronic excited state. Such a vibronic coupling is known to cause a distortion in the equilibrium conformation of the molecule (Jahn-Teller distortion) from the symmetrical conformation, and the Raman scattering tensor is found to be calculated by the use of the amount (δ) of this distortion as an empirical parameter. It has been suggested that some of the Raman lines for the degenerate stretching vibrations, which become stronger with the exciting frequency, in some molecules, are caused by such Jahn-Teller couplings. For the intensity of the Raman line at 887 cm^?1 of the degenerate stretching vibration of chromate anion, a slightly more detailed examination has been made, and the amount of the Jahn-Teller distortion in a $\text{B}\text{?}$ (T₂) electronic state has been estimated to be 0.2₀ Å amu^1/2 along the normal coordinate of this vibration.     

飞秒强激光场中水分子的电离激发

本文运用含时密度泛函理论和分子动力学非绝热耦合的方法, 研究了水分子在不同极化方向的激光场中的电离和动力学行为. 计算结果表明, 对应相同的极化方向, 随着激光强度的增加, 水分子的电离增强; 对于相同强度的激光, 当激光极化方向沿水分子对称轴方向时, 水分子的电离最强, 当激光极化方向垂直水分子对称轴方向时, 水分子电离受到最大程度的抑制. 对水分子偶极矩的研究表明, 当分子处于线性响应区域时, x方向的激光只能激发起x方向的偶极振动而y方向的激光只能激发起y方向的偶极振动. 对水分子的键长和键角的研究表明, 在激光场中水分子的键长变长, 键角变大, 但变化幅度随着激光极化角的增大而减小. 此外, 研究还发现, 虽然在不同极化方向的激光脉冲的驱动下, 水分子OH键的振动频率与激光频率相当, 在脉冲关闭后, 振动频率减小, 但激光场的极化方向对水分子振动模式具有选择性. 关键词： 含时密度泛函理论 分子动力学 水分子 电离     

Two-dimensional condensation of water and alcohols on NaF

On the surface of NaF the adsorption isotherms of H₂O, D₂O, CH₃OH, C₃H₃OH and 1-C₃H₇OH as well as the infrared spectra of H₃O, D₂O, dilute HDO, CH₃OH and CH₃OD were measured. The adsorption temperatures of H₃O (253–308 K) were within the phase transition region where two phases of low and high density coexist, while those of CH₃OH, C₂H₅OH and 1-C₃H₃OH were yet within a super-critical region. The entropy of the 2D condensed H₂O on NaF was found to be 14.0 cal K^?1 mol^?1, which suggests that the condensed phase of water on NaF is liquid-like. The OD stretching band of dilute HDO in the 2D condensed water gives a maximum adsorption at ca. 2530 cm^?1 with a half width of ca. 150 cm^?1, being in good agreement with that in liquid water. Comparison of the integrated absorbance of the D₂O bending mode with that of the OD stretching mode suggests that the cluster size of the 2D condensed water on NaF decreases with increasing temperature. The 2D critical temperature and the occupied areas of these adsorbates enable us to conclude that the compatibility of the molecular size with the surface lattice is not important in the occurrence of the 2D condensation of the hydrogen-bonding molecules on NaF and that adsorbed molecules are randomly oriented on the surface to the extent similar to that in 3D liquid state.