An ab initio calculation of symmetric bending and stretching vibrational states of the H3O+ and D3O+ ions

Calculations are reported for the symmetric bending and stretching vibrational states of H₃O⁺ and D₃O⁺ including coupling between these two modes. The calculations were carried out by using a potential surface calculated by the SCF CI method and expressed in terms of symmetric internal coordinates. The transition energy of the ν₂ (1^? ← 0⁺) inversion mode is found to be 985 cm^?1, which is comparable to the experimental value of 954.417 cm^?1 observed by Haese and Oka. The calculated inversion doubling of the lowest state is 51 cm^?1.     

Modeling Chemical Composition for an Atmospheric Pressure DC Discharge in Air with Water Cathode by 0-D model

This paper reports the results of the chemical composition modeling for an atmospheric pressure DC air discharge with water cathode. The modeling was based on the combined solution of Boltzmann equation for electrons, equations of vibrational kinetics for ground states of N₂, O₂, H₂O and NO molecules, equations of chemical kinetics and plasma conductivity equation. Calculations were carried out using experimental values of E/N and gas temperatures for the discharge currents range of 20–50 mA. The effect of H₂O concentration on the plasma composition was studied. The main particles of plasma were shown to be O₂(a¹Δ, b¹Σ), O(³P), NO, NO₂, HNO₃, H₂O₂ and OH. Effective vibrational temperatures of molecules were higher than gas temperature and they did not depend on the discharge current. Distribution functions on vibrational levels for N₂, O₂, H₂O and NO ground states were non-equilibrium ones.     

Overtone spectrum in terms of normal or of equivalent modes with application to H2O

An algebraic hamiltonian which closely fits the (low and) high stretching vibrational spectrum of H₂O (and of other YXY molecules such as O₃) is shown to correspond to two weakly coupled equivalent modes.     

Vibrational co-assignment of the calculated frequencies in the ground and two lowest excited electronic states

The feasibility of co-assignments of the vibrational frequencies in the ground and T₁ and S₁ excited electronic states has been demonstrated for trans-C₂O₂F₂. Matrices analogous to the Duschinsky matrix were used to juxtapose the vibrational frequencies of this molecule calculated at the CASPT2/cc-pVTZ level in the ground S₀ and excited triplet T₁ and singlet S₁ electronic states. The calculations suggest that the calculated CC and CF stretching frequencies of trans-C₂O₂F₂ in these three electronic states should be mutually reassigned in comparison with the previous interpretation.     

Na2O-P2O5系晶体微结构形态的拉曼光谱研究及其ab initio计算

本文采用激光拉曼光谱仪测量了磷酸钠二元系(1-x)Na₂O·xP₂O₅(x=0.25,0.33,0.50,1.0)几种晶体的拉曼光谱,比较并解释了随化学组成而变化微结构单元的拉曼振动模。同时用Gaussian 98W量子化学软件从头计算了这几种化合物的拉曼光谱。实验和计算均表明,磷酸盐晶体的基本结构单元为磷氧四面体[PO₄],并且晶体中磷氧四面体的伸缩模振动频率与连接中心磷原子的桥氧数密切相关,随桥氧数增加而升高。此外还解释了模拟图谱与实验谱差异的原因。     

Vibrational transition moment directions of a terminally p-nitrobenzyl substituted long-chain alkanethiol by polarized infrared spectra and DFT calculations

Transition moment directions of the vibrational states of nitro and carbonyl groups of p-nitrobenzyl-16-mercaptohexadecanoate are evaluated by infrared linear dichroism (IR LD) to be further exploited as film orientation markers in self-assembled monolayers (SAMs) that the respective compound forms on metal surfaces. DFT calculations followed by a complete normal coordinate analysis were employed to assist in the vibrational bands assignments. The analysis of the experimental IR LD spectra in conjunction with the step-wise reduction procedure of Thulstrup–Eggers indicated that the transition moment directions of the antisymmetric NO₂ stretching and the carbonyl stretching modes are collinear, and confirmed previous results that those of the symmetric and the antisymmetric NO₂ stretching vibrations are not exactly mutually perpendicular.     

TD-DFT Study on the Excited-State Hydrogen Bonding of the p-Cresol–NH3–H2O Complex

In this work, the time-dependent density functional theory (TD-DFT) method was used to study the electronic excited-state dynamics of the hydrogen-bonded p-Cresol–NH₃–H₂O complex. The intermolecular hydrogen bonds O₁–H₁···N and C–O₁···H₂ were demonstrated by the optimized geometric structure of the hydrogen-bonded p-Cresol–NH₃–H₂O complex. The infrared spectra (IR spectra) of the hydrogen-bonded p-Cresol–NH₃–H₂O complex in the ground and excited states were also calculated by using the density functional theory (DFT) and TD-DFT methods. It is demonstrated that hydrogen bond O₁–H₁···N can be strengthened while hydrogen bond C–O₁···H₂ is weakened upon photoexcitation to the S₁ state. The significant changes of the hydrogen bond from the calculated bond lengths in different electronic states can be observed. In addition, the spectral shifts of the stretching vibrational mode of the hydrogen-bonded O–H group in different electronic states are accounted for the hydrogen bond changes in the S₁ state too.     

Electrical conductivity and dielectric behaviour of PPG4�CAgCF3SO3:Al2O3 nanocomposite gel polymer electrolyte system

In this report, the synthesis of solvent-free poly(propylene glycol) 4000 (PPG₄)?Csilver triflate (AgCF₃SO₃):xAl₂O₃ nanocomposite gel polymer electrolytes containing four different amounts of Al₂O₃ nanoparticles corresponding to x?=?1, 3, 5 and 7?wt.%, respectively, with an ether oxygen-to-metal cation ratio (O?CM) of 4:1 together with their vibrational spectroscopic characteristics derived from Fourier transform infrared (FT-IR ) spectroscopic analysis at room temperature (25?°C) is described. Furthermore, a detailed investigation concerning their mechanism of ion transport performed by means of complex impedance analysis in the frequency range 20?Hz to 1?MHz and over the temperature region 25?C90?°C and analysed in terms of electrical conductivity spectra, electrical modulus spectra and impedance spectra has indicated that the typical composition PPG₄?CAgCF₃SO₃:5?wt.% Al₂O₃ would exhibit the best room temperature electrical conductivity of 6.2?×?10^?4?S cm^?1 owing to the mobility of coordinated silver cations through the mechanism of enhanced segmental motion of the PPG₄ polymer chains as aided by the various coordinating sites available within the polymer network. It is also demonstrated from the present FT-IR results that significant changes in the intensity, shape and position of the different vibrational bands corresponding to ?COH stretching, C?CO?CC stretching, C?CH stretching and C?CO?CC in C?CH stretching modes occur as a result of the incorporation of Al₂O₃ nanofiller particles into the PPG₄?CAgCF₃SO₃ complex. It is evident from the conductivity data that the observed enhancement in electrical conductivity would result from appropriate changes in ionic association occurring in the form of probable ion?Cion and ion?Cpolymer interactions involving Al₂O₃ nanofiller additive in accordance with the Lewis acid?Cbase model of polymer?Csalt?Cfiller interactions.     

IR,Raman, and Surface‐enhanced Raman Spectroscopic Study on Triruthenium Dipyridylamide Diruthenium Nickel Dipyridylamide Family: Metal‐metal Bonding and Structures

We report the infrared, Raman, and surface‐enhanced Raman scattering (SERS) spectra of triruthenium dipyridylamido complexes and of diruthenium mixed nickel metal‐string complexes. From the results of analysis on the vibrational modes, we assigned their vibrational frequencies and structures. The infrared band at 323–326 cm^?1 is assigned to the Ru₃ asymmetric stretching mode for [Ru₃(dpa)₄Cl₂]^0–2+. In these complexes we observed no Raman band corresponding to the Ru₃ symmetric stretching mode although this mode is expected to have substantial Raman intensity. There is no frequency shift in the Ru₃ asymmetric stretching modes for the complexes with varied oxidational states. No splitting in Raman spectra for the pyridyl breathing line indicates similar bonding environment for both pyridyls in dpa^– , thus a delocalized structure in the [Ru₃]^6–8+ unit is proposed. For Ru₃(dpa)₄(CN)₂ complex series, we assign the infrared band at 302 cm^?1 to the Ru₃ asymmetric stretching mode and the weak Raman line at 285 cm^?1 to the Ru₃ symmetric stretching. Coordination to the strong axial ligand CN^– weakens the Ru‐Ru bonding. For the diruthenium nickel complex [Ru₂Ni(dpa)₄Cl₂]^0–1+, the diruthenium stretching mode ν_Ru‐Ru is assigned to the intense band at 327 and 333 cm^?1 in the Raman spectra for the neutral and oxidized forms, respectively. This implies a strong Ru‐Ru metal‐metal bonding.     

Relaxation mechanism of the 1Δg state of liquid O2

Collisional deactivation of the first excited electronic ¹Δ_g(υ = 0) state of O₂ involves intersystem crossing to higher vibrational levels (υ < 5) of the electronic ground state ³Σ^?_g. It is followed by rapid vibrational-vibrational energy exchange which populates the first excited ³Σ^?_g(υ = 1) vibrational level. The suggested relaxation mechanism is supported by experimental results on the time dependence of the populations of the ¹Δ_g(υ = 0) and ³Σ^?_g(υ = 1) states in liquid natural O₂ and ¹⁸O₂.     

On the studies of the vibrational spectra of cluster [Mo2O2S2(S2)2]2-

IR and Raman spectra of [Mo₂O₂S₂(S₂)₂]^2- were reported. The resonance Raman spectra and the depolarization ratios in CH₃CN solution were measured. By using the data of crystal structure, the simplified normal coordinate calculation of the stretching vibrations for anion [Mo₂O₂S₂(S₂)₂]^2- was performed. The results obtained are useful to assign the vibrational bands of some Mo-Fe-S clusters.     

The rotational spectrum of the hydrogen-bonded heterodimer H2O…HF in the frequency range 40–80 GHz

The μ_a R-branch rotational spectra of the ground and first excited states of the three lowest vibrational modes of the H₂O…HF heterodimer have been observed in the frequency range 40–80 GHz. Coriolis perturbations between the ground vibrational state (υ = 0) and the first excited state of the out-of-plane bending vibration (υ_β(0) = 1) show that for a given J the K₋₁ = 2 levels of υ_β(0) = 1 lie approximately 3 cm⁻¹ above the K₋₁ = 3 levels of υ = 0. The vibrational separation between these two states is estimated to be 70±3 cm⁻¹. This value is consistent with those determined by other methods and reinforces the conclusion that ν_β(0) is governed by a double-minimum potential energy function with the quantitative form previously published. A perturbation is also observed in the first excited state of the hydrogen-bond stretching vibration υ_σ = 1. This manifests itself as a large, negative centrifugal distortion constant D_JK = −8.5 MHz compared with 2 MHz in the other vibrational states.     

Charge exchange of O2+ with Cs: spectroscopy and predissociation pathways for the Πg Rydberg states of O2

Electron capture by keV O₂⁺ (X₂Π_g) ions from Cs atoms yields predominantly the ¹Π_g and ³Π_g Rydberg states of O₂ which subsequently predissociate. Through the use oftranslational spectroscopy on the neutral product atoms, we have located a number of vibrational levels of these states and determined the dissociation channels. Furthermore we have observed competition between diabatic and adiabatic behaviour in the dissociating channels.     

Reaction of CH3O2 and HO2: Ab initio characterization of dimer structure and vibrational mode analysis for reaction mechanisms

All species involved in the multi‐channel reaction of CH₃O₂ with HO₂ have been investigated using density functional theory (DFT). The molecular geometries for various species are optimized employing the B3LYP method implementing the 6‐311++G** basis set. The relative energies of all species are calculated at the same level theory. The results show that there are two kinds of channels: singlet and triplet. The singlet channel involves four intermediates and six transition states. The triplet channel includes two intermediates and two transition states. There are four kinds of reaction products: CH₃OOH + ¹O₂, CH₃OH + O₃, CH₄ + 2O₂, and CH₃OOH + ³O₂. The vibrational mode analysis is used to elucidate the relationships of the intermediates, the transition states, and the products. The extensive investigation shows that the reaction mechanism is reliable. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

On some controversy regarding νOH assignments in CsH2PO4

Spectroscopic methods such as Raman scattering and IR absorption, as well as structural methods such as x-ray and n-diffraction, offer rather ambiguous interpretation of the high-frequency phonon spectrum of CsH₂PO₄ (CDP), especially regarding the proper assignment of proton vibrational modes. Empirical lattice dynamics (LD) simulations of the proton vibrational density of states ((H-VDOS)) in CDP also reveal a discrepancy in the frequency assignments of the OH stretching modes of its two non-equivalent hydrogen bonds. This may be resolved by accounting for the LD simulated directional (H-VDOS) along the three Cartesian axes of CDP, from which the corresponding anisotropy of the proton kinetic energy tensor can be deduced. The results may then be tested by a simple deep inelastic neutron scattering (DINS) measurement on a single crystal of para-electric CDP at room temperature.     

Methanol Adsorption on TiO2 Film Studied by Sum Frequency Generation Vibrational Spectroscopy (cited:2)

A broadband infrared surface sum frequency generation vibrational spectroscopy (SFG-VS) and an in situ UV excitation setup devoted to studying surface photocatalysis have been constructed. With a home-made compact high vacuum cell, organic contaminants on TiO₂ thin lm surface prepared by RF magnetron sputtering were in situ removed under 266 nm irradiation in 10 kPa O₂ atmosphere. We obtained the methanol spectrum in the CH₃ stretching vibration region on TiO₂ surface with changing the methanol pressure at room temperature. Features of both molecular and dissociative methanol, methoxy, adsorbed on this surface were resolved. The CH₃ symmetric stretching vibration frequency and Fermi resonance of molecular methanol is red-shifted by about 6?8 cm^-1 from low to high coverage. Moreover, the recombination of dissociative methanol and H on surfaces in vacuum was also observed. Our results suggest two equilibria exist: between molecular methanol in the gas phase and that on surfaces, and between molecular methanol and dissociative methanol on surfaces.     

IR spectroelectrochemical studies of Fe2V4O13, FeVO4 and InVO4 thin films obtained via sol-gel synthesis

In this paper we generalize the IR spectroscopic properties of M³⁺VO₄ (M=Fe, In) orthovanadate and Fe₂V₄O₁₃ films. The films were prepared using the sol-gel synthesis route from M³⁺ nitrates and vanadium oxoisopropoxide. The vibrational bands in the IR absorbance spectra of the films are classified in terms of terminal V-O stretching (1050–880 cm^–1), bridging V-O^...Fe and V^...O^...Fe stretching (880–550 cm^–1), mixed V-O-V deformations and Fe-O stretching (<550 cm^–1) modes. Ex situ IR spectra of films were measured after consecutive charging/discharging to various intercalation coefficients x and correlated to the current peaks in the cyclic voltammetry curves measured in 1 M LiClO₄/propylene carbonate electrolyte. We classified the ex situ IR spectra of charged/discharged films according to their vibrational band changes. The results reveal that, for small values of the intercalation coefficient, crystalline FeVO₄, InVO₄ and Fe₂V₄O₁₃ films exhibit a simultaneous decrease in the intensity of all IR bands while the band frequencies remain unaffected. For the higher intercalation levels, IR mode frequencies are shifted, signaling the presence of reduced vanadium. Further charging leads to an amorphization of the film structure, which was established from the similarity of the IR spectra of charged films with those of amorphous films prepared at lower annealing temperatures. The results confirm that ex situ IR spectroelectrochemical measurement is an effective way to assess the structural changes in films with different levels of intercalation. Electronic Publication     

FT-IR photoacoustic spectra of the surface of Ru3(CO)12/Al2O3 system

The FT-IR photoacoustic spectra of Ru₃(CO)₁₂/Al₂O₃ (acidic and basic alumina) system have been measured for different ageing times. The behaviors of oxidation states of Ru on the surface of basic or acidic alumina and their difference are discussed on the ground of CO stretching bands of their spectra.     

Resonance CARS spectra of 9,9′-bianthryl in the excited states

Resonance CARS spectra of 9,9′-bianthryl in the twisted intramolecular charge-transfer (TICT), locally excited (LE)-S₁ and T₁ states were obtained in solution at room temperature. Observed Raman frequencies were compared with those of the S₀ state, the values of anthracene in the S₁, T₁ and radical ion states. The results show those vibrational modes of bianthryl not only in the S₀ state but also in the LE-S₁, TICT and T₁ states more or less consist of those of anthracene moieties. The inter-moiety CC stretching vibrational mode was not observed in the excited states.     

The photodissociation of vibrationally excited ozone in the upper atmosphere

The photodissociation of vibrationally excited O₃ in the sunlit mesosphere is investigated. Dissociation rate coefficients for specific vibrationally excited states of O₃ are calculated for the conditions of an overhead sun. Possible vibrational enhancements of the O(¹D) and O₂(a¹Δ_g) production rates are assessed. It is shown that such enhancements should make only minor contributions to the daytime production of these species in the mesosphere and lower thermosphere.