The infrared spectrum of VO(OH)2 (synthetic duttonite)

The infrared spectra of normal and deuterated VO(OH)₂ were recorded and are briefly discussed on the basis of its structural characteristics.     

Theoretical investigation of the SO(2+) dication and the photo-double ionization spectrum of SO

Highly correlated ab initio methods were used in order to generate the potential energy curves of the electronic states of the SO(2+) dication and of the electronic ground state of the neutral SO molecule. These curves were used to predict the spectroscopic properties of this dication and to perform forward calculations of the double photoionization spectrum of SO. In light of spin-orbit calculations, the metastability of this doubly charged ion is discussed: for instance, the rovibrational levels of the X (1)Sigma(+) and A (3)Sigma(+) states are found to present relatively long lifetimes. In contrast, the other electronic excited states should predissociate to form S(+) and O(+) in their electronic ground states. The simulated spectrum shows structures due to transitions between the v=0 vibrational level of SO (X (3)Sigma(-)) and the vibrational levels below the barrier maximum of 11 of the calculated electronic states. The 2 (1)Sigma(+) electronic state of SO(2+) received further treatment: in addition to vibrational bands due to the below barrier energy levels of this electronic state, at least nine continuum resonances were predicted which are responsible for the special shape of the spectrum in this energy region. This work is predictive in nature and should stimulate future experimental investigations dealing with this dication.     

液相色谱柱后衍生法同时测定Pb~(2+)Cu~(2+)Cd~(2+)Co~(2+)Zn~(2+)和Ni~(2+)

采用液相色谱流动相为0.05mol·L~(-1)草酸和0.095mol·L~(-1)氢氧化锂,流速为1.0ml·min~(-1);柱后衍生试剂为0.001mol·L~(-1)PAR+0.3mol·L~(-1)氨水+0.1mol·L~(-1)乙酸,流速为1.0ml·min~(-1),进样体积为20μl,检测波长为500nm,同时对Pb~(2+)、Cu~(2+)、Cd~(2+)、Co~(2+)、Zn~(2+)和Ni~(2+)检测。方法可用于水样检测。     

The infrared spectrum of Au-.CO2

The Au-.CO2 ion-molecule complex has been studied by gas phase infrared photodissociation spectroscopy. Several sharp transitions can be identified as combination bands involving the asymmetric stretch vibrational mode of the CO2 ligand. Their frequencies are redshifted by several hundred cm(-1) from the frequencies of free CO2. We discuss our findings in the framework of ab initio and density-functional theory calculations, using anharmonic corrections to predict vibrational transition energies. The infrared spectrum is consistent with the formation of an aurylcarboxylate anion with a strongly bent CO2 subunit.     

On the infrared spectrum and force constants of the Tetrafluorochlorate (III) Anion,CIF

The previously reported infrared spectrum of CIF₄^? is corrected. A new set of force constants was calculated for CIF₄^? based on the revised assigment.     

Molecular orbital anharmonic estimates for the infrared spectrum of CO2

The vibrational spectrum of CO2 up to second overtones has been calculated at four different ab initio levels using second order perturbation theory equations in a simplified manner, in which just a few cross-terms suitable for numerical estimation are considered in the Taylor series representing the potential energy and dipole moment functions. The series coefficients are obtained through polynomial regression of estimated single point energy and dipole values for a few distorted geometries along each normal coordinate. The effect of Fermi resonance on near-degenerate energy levels was also taken into account through the usual first order perturbation equations. MP2/6-31G(extended) frequency estimates have a root mean square error of just 32.14 cm(-1). This accuracy is achieved partly due to the underestimation of the harmonic frequencies, which compensates for the neglect of the cross-term chi(ij) anharmonic constants. The chi(ii) constants which depend on cubic and quartic energy coefficients are reasonably well estimated at all ab initio levels. The energy coefficient beta(sbb) responsible for the magnitude of the Fermi resonance is estimated with a maximum error of just 13%. Despite the inclusion of anharmonicities, errors for band intensities are still much larger than for the frequencies. Both electrical and mechanical anharmonicities may be equally important to the band intensity.     

A vibrational study of the infrared spectrum of dibromodifluoromethane,CBr2F2

The i.r. spectrum of natural dibromodifluoromethane has been recorded at medium resolution in liquid phase and at moderately high resolution in vapor phase. A number of regions have been analysed and the vibrational and vibrational—rotational features of the observed spectral structures interpreted. The frequency values pertaining to the fundamentals of the bromine isotopic species have been either directly measured or evaluated by “difference” bands and their isotopic splitting checked by a normal coordinates calculation. Absorptions due to the minor component ¹³CBr₂F₂ have also been observed and in part assigned.     

Rotationally resolved infrared spectrum of the Li+-D2 cation complex

The infrared spectrum of mass selected Li(+)-D(2) cations is recorded in the D-D stretch region (2860-2950 cm(-1)) in a tandem mass spectrometer by monitoring Li(+) photofragments. The D-D stretch vibration of Li(+)-D(2) is shifted by -79 cm(-1) from that of the free D(2) molecule indicating that the vibrational excitation of the D(2) subunit strengthens the effective Li(+)cdots, three dots, centeredD(2) intermolecular interaction. Around 100 rovibrational transitions, belonging to parallel K(a)=0-0, 1-1, and 2-2 subbands, are fitted to a Watson A-reduced Hamiltonian to yield effective molecular parameters. The infrared spectrum shows that the complex consists of a Li(+) ion attached to a slightly perturbed D(2) molecule with a T-shaped equilibrium configuration and a 2.035 A vibrationally averaged intermolecular separation. Comparisons are made between the spectroscopic data and data obtained from rovibrational calculations using a recent three dimensional Li(+)-D(2) potential energy surface [R. Martinazzo, G. Tantardini, E. Bodo, and F. Gianturco, J. Chem. Phys. 119, 11241 (2003)].     

State-resolved UV photofragmentation spectrum of the metal dication complex [Zn(pyridine)(4)](2+)

A combined theoretical and experimental study of electronic transitions in the complex [Zn(pyridine)(4)](2+) provides the first example of a state-resolved electronic spectrum to be recorded for a dication complex in the gas phase.     

Completing the 3d metal fluoride series: the pure rotational spectrum of ZnF (X2Sigma+)

The pure rotational spectrum of the ZnF radical has been recorded in the range of 176-527 GHz using millimeter/submillimeter direct absorption techniques. This study is the first gas-phase spectroscopic investigation of this species. Between 5 and 11 transitions were measured for each of five isotopologues of this radical (64ZnF, 66ZnF, 67ZnF, 68ZnF, and 70ZnF) in the ground and several excited vibrational (v=1, 2, and 3) states. Each transition consists of spin-rotation doublets with a splitting of approximately 150 MHz, indicating that the electronic ground state of ZnF is 2Sigma+, as predicted by theory. Fluorine hyperfine splitting was observed in three isotopologues (64ZnF, 66ZnF, and 67ZnF), and hyperfine structure from the zinc-67 nucleus (I=52) was additionally resolved in 67ZnF. Rotational, fine structure, and 19F and 67Zn hyperfine constants were determined for ZnF, as well as equilibrium parameters. The bond length of the main isotopologue 64ZnF was calculated to be re=1.7677 A. Evaluation of the hyperfine constants indicates that the sigma orbital containing the unpaired electron is approximately 80% 4s(Zn) in character with approximately 10% contributions from each of the 2p(F) and 4p(Zn) orbitals. These results imply that ZnF is somewhat less ionic than CaF, as suggested by theory.     

Theoretical infrared spectrum of the ethanol hexamer

The hydrogen bond network of ethanol clusters is among the most complex hydrogen bond networks of molecular clusters. One of the reasons of its complexity arises from the number of possible ethanol monomers (there are three isoenergetic isomers of the ethanol monomer). This leads to difficulties in the exploration of potential energy surfaces (PESs) of ethanol clusters. In this work, we have explored the PES of the ethanol hexamer at the MP2/aug-cc-pVDZ level of theory. We have provided structures and their relative stability at 0 K and for temperatures ranging from 20 to 400 K in the gas phase. These structures are used to compute the theoretical infrared (IR) spectrum of the ethanol hexamer at the MP2/aug-cc-pVDZ level of theory. As a result, 98 different structures have been investigated, and six isomers are reported to be the most isoenergetically stable structures of the ethanol hexamer. These isomers are folded cyclic structures in which the stability is enhanced by the implication of CH⋯O interactions. Our investigations show that the PES of the ethanol hexamer is very flat, yielding several isoenergetic structures. Furthermore, we have noted that several isomers contribute to the population of the ethanol hexamer at high temperatures. As far as the IR spectroscopic study is concerned, we have found that the IR spectra of the most stable structures are in good agreement with the experiment. Considering this agreement, these structures are used to assign the experimental peaks in the CH-stretching region. We concluded that the stability of the structures of the ethanol hexamer is related both to OH⋯O hydrogen bonds and CH⋯O interactions. Overall, we have found that the IR spectrum of the ethanol hexamer, calculated from the contribution of all the possible stable structures weighted by their probability, excellently reproduce the experimental spectrum of the ethanol hexamer.     

Far infrared spectrum of silane

The absorption spectrum of SiH₄ from 32 to 400 cm^?1 has revealed two sepasrate bonds,one linear in density and one quadratic.From the linear band,the electric dipole moment produced in the ground vibronic state by centrifugal distortion effects has been estimated to be 9.3 × 10^?6 D in magnitude. From the quadratic band, the molecular octopole moment has been determined to be 3.0 × 10^?34 esu cm³ in magnitude. The simplicity of the techniques used is stressed.     

Theoretical and experimental studies of the infrared rovibrational spectrum of He2-N2O

Rovibrational spectra of the He(2)-N(2)O complex in the nu(1) fundamental band of N(2)O (2224 cm(-1)) have been observed using a tunable infrared laser to probe a pulsed supersonic jet expansion, and calculated using five coordinates that specify the positions of the He atoms with respect to the NNO molecule, a product basis, and a Lanczos eigensolver. Vibrational dynamics of the complex are dominated by the torsional motion of the two He atoms on a ring encircling the N(2)O molecule. The resulting torsional states could be readily identified, and they are relatively uncoupled to other He motions up to at least upsilon(t) = 7. Good agreement between experiment and theory was obtained with only one adjustable parameter, the band origin. The calculated results were crucial in assigning many weaker observed transitions because the effective rotational constants depend strongly on the torsional state. The observed spectra had effective temperatures around 0.7 K and involved transitions with J < or =3, with upsilon(t) = 0 and 1, and (with one possible exception) with Deltaupsilon(t)=0. Mixing of the torsion-rotation states is small but significant: some transitions with Deltaupsilon(t) not equal 0 were predicted to have appreciable intensity even assuming that the dipole transition moment coincides perfectly with the NNO axis. One such transition was tentatively assigned in the observed spectra, but confirmation will require further work.     

Origin of spurious bands in the infrared spectrum of Ba2TiO4

The IR spectrum of Ba₂TiO₄ synthesized from “pure” commercial samples of TiO₂ and BaCO₃ exhibits between 1200 and 950 cm⁻¹ a more-or-less complex pattern of sharp, very weak bands whose intensity depends on the origin of the reagents, and which disappear completely if very pure reagents are used for the synthesis. It is shown that most of these bands are due to a small quantity (e.g. 0.5 mole % or less) of phosphate and/or sulfate ions (brought by the reagents) replacing the TiO₄ tetrahedra in the Ba₂TiO₄ structure and thus forming a “dilute” solid solution. This is responsible for the sharpness of the IR bands and for their easy observation, even at fairly low concentrations [e.g. 0.1 mole % for the (PO₄)³⁻ ion]. The four investigated TiO₂ samples are free from sulfate, but all of them (including pro analysi samples) contain a small amount (0.5-0.1%) of phosphate, not disclosed in TiO₂ itself, but easily evidenced after transformation into Ba₂TiO₄.     

Ab initio calculations of the rotationally resolved infrared spectrum of KNa 2 +

Summary Ab initio variational calculations were performed on the rotationally resolved infrared spectrum of KNa ₂ ⁺ . A discrete potential energy surface was generated using the configuration interaction ansatz coupled with the frozen core approximation, from which an analytical representation was obtained using a power series expansion employing a Dunham expansion variable. This force field was embedded in an Eckart-Watson rovibrational Hamiltonian, from which eigenfunctions and eigenenergies were calculated. An SCF dipole moment surface was generated and used to calculate absolute line intensities and square dipole matrix elements between the vibrational ground state and the lowest-lying excited states for some of the most intense transitions within the P, Q and R branches.     

Determination of the hyperfine coupling constant and zero-field splitting in the ESR spectrum of Mn(2+) in calcite

The hyperfine coupling constant (A in units of energy or A' in units of magnetic field) and zero-field splitting (D in units of energy or D' in units of magnetic field) in the ESR spectrum of Mn(2+) in calcite were determined. The spreading of the non-central allowed transitions |3/2, m --> |5/2, m, |1/2, m --> |3/2, m, |-3/2, m --> |-1/2, m and |-5/2, m --> |-3/2, m was analysed and the experimental transitions were attributed. Particular relevance was given to the difference between the two types of resonances, shoulder or divergence, and to their origin (M, m). The analysis explains the presence of a weak shoulder between each of the five central doublets |-1/2, m --> |1/2, m. Six independent methods for calculating the hyperfine coupling constant and five methods for calculating the zero-field splitting, based on the analysis of the allowed and forbidden transitions, were provided. The values of the hyperfine coupling constant range from -93.9 to -94.6 G and those of the zero-field splitting range from -79.5 to -80.5 G. A critical evaluation of the advantages and drawbacks of the 11 methods is included: the best value for A' is -94.30 G and that for D' is -79.95 G.     

Concerning the photophysical properties of Re2(4+) and Re2(6+) carboxylate compounds

The preparation and structure of Re(2)(dppm)(2)(O(2)CC(6)H(4)-p-NO(2))(2)Cl(2), where dppm = Ph(2)PCH(2)PPh(2), is reported together with its photophysical properties (absorption, steady state emission, fs- and ns-transient absorption spectroscopy) and electrochemistry. These data are compared with photophysical studies on the previously reported Re(2)(dppm)(2)(O(2)CCH(3))(2)Cl(2). The preparation of the complex Re(2)(O(2)CC(6)H(4)-p-NO(2))(4)Cl(2) is also reported together with its photophysical properties which allows for a comparison of the electronic structures and photophysical states of Re(2)(4+) and Re(2)(6+) containing complexes having MM configurations σ(2)π(4)δ(2)δ(*2) and σ(2)π(4)δ(2), respectively. An interesting comparison is also made with the related MM quadruply bonded complexes of molybdenum and tungsten.     

Approximate molecular orbital anharmonic parameters for the infrared spectrum of H2O

The vibrational spectrum of H2O was calculated at MP2/6-31G(extended) and MP2/6-311G* levels taking into account anharmonicities through a simple approach to second-order perturbation theory in which molecular energy and dipole moment are expanded as Taylor series in normal coordinates with no cross terms, to simplify calculations. The series coefficients are obtained separately for each normal coordinate through polynomial regression of calculated single point property values corresponding to a few distorted molecular geometries. The energy coefficients are used to calculate the harmonic frequencies and the chi(ii) anharmonicity constants, and so the band origins. For the band intensities, second-order perturbation theory equations derived earlier for diatomic molecules are used for each mode. Estimated frequencies have accuracy equivalent to those of previous complete perturbation calculations at the same ab initio levels, being at most 2.6% above the experimental values for the MP2/6-31G(extended) level. The fundamental intensity estimates are equivalent to those for the complete treatments, with the exception of that at MP2/6-31G(extended) level for the bending mode, which is 7% above the experimental value. Estimated overtone intensities by both complete treatments and the simple approach may still differ in magnitude from the experimental values, though to a lesser extent for the formers.     

The effect of triethylenetetraamine (Trien) on the ion flotation of Cu(2+) and Ni(2+)

Ion flotation is a separation process involving the adsorption of a surfactant and counterions at an air/aqueous solution interface. It shows promise for removing toxic heavy metal ions from dilute aqueous solutions. Here we report the effect of a neutral chelating ligand, triethylenetetraamine (Trien), on the ion flotation of cations with dodecylsulfate, DS(-), introduced as sodium dodecylsulfate, SDS. Ion flotation in the aqueous SD-Cu(II)-Ca(II)-Trien system gave strongly preferential removal of Cu(II) over Ca(II), which is a reversal of the order of selectivity seen in the SDS-Cu(II)-Ca(II) system containing no Trien. The removal rates of Cu(2+) and Ni(2+) with DS(-) were much faster in the presence of Trien than for simple aquo ions, and the final metal concentration was significantly lower. Surface tension measurements showed that Trien enhanced the surface activity and adsorption density for SDS-Cu(II) and SDS-Ni(II) solutions. The overall change in the Gibbs free energy for adsorption resulting from complexation was -3.60 kJ/mol for Cu(II) and -3.50 kJ/mol for Ni(II). This included the effects of hydrophobic interactions between the metal-Trien complexes at the air/solution interface, along with changes in the amount of dehydration associated with cosorption of the metal-Trien complex with DS(-) at the air/solution interface.