The bending energy levels of C2H2

Absorption spectra of C₂H₂ have been recorded between 50 and 1450 cm⁻¹, with a resolution always better than 0.005 cm⁻¹, using two different Fourier transform spectrometers. Analysis of the data provided two sets of results. First, the bending levels with Σ_t V_t(t = 4, 5) ≤ 2 were characterized by a coherent set of 34 parameters derived from the simultaneous analysis of 15 bands, performed using a matrix Hamiltonian. The following main parameters were obtained (in cm⁻¹): ω₄⁰ = 608.985196(14), ω₅⁰ = 729.157564(10); B₀ = 1.17664632(18), α₄ = −1.353535(86) × 10⁻³, α₅ = −2.232075(40) × 10⁻³; q₄⁰ = 5.24858(12) × 10⁻³, and q₅⁰ = 4.66044(12) × 10⁻³, with the errors (1σ) on the last quoted digit. Second, a more complete set of bending levels with Σ_t V_t ≤ 4, some of which have never previously been reported, and also including V₂ = 1 have been fitted to 80 parameters. This simultaneous fit involved 43 bands and used the same full Hamiltonian matrix. Some perturbations which affect the higher excited levels are discussed.     

Photophysics of bis-bipyridyl complexes of ruthenium(II) with triphenylphosphine

We studied the spectral-luminescent characteristics of the luminescence of mixed-ligand polypyridine-phosphine complexes of ruthenium(II) cis-[Ru(bpy)₂(PPh₃)X](BF₄) _n with ligands 2,2′-bipyridyl (bpy) and triphenylphosphine (PPh₃) and X = Cl⁻, Br⁻, CN⁻, NO₂⁻, NH₃, MeCN, pyridine (py), 4-aminopyridine (pyNH₂), and 4,4′-bipyridyl (4,4′-bpy) in a 4: 1 EtOH-MeOH alcoholic mixture at 77 K. The radiative and nonradiative deactivation rate constants of the lowest electronically excited state of the complexes are determined. We find that triphenylphosphine has a greater effect on the photophysical characteristics of ruthenium(II) complexes compared to π-acceptor strong-field ligands, such as MeCN, CN⁻, and NO₂⁻. At the same time, the characteristics of complexes cis-[Ru(bpy)₂(PPh₃)X] ⁿ⁺ considerably depend on the nature of the second monodentate ligand X, which is coordinated to ruthenium(II), and correlate with its position in the spectrochemical series of ligands.     

Interaction of oxovanadium(IV) with carboxylic ligands in aqueous solution: A thermodynamic and visible spectrophotometric study

The hydrolysis of VO²⁺ and the complex with sulfate were studied potentiometrically, spectrophotometrically and calorimetrically, in NaCl aqueous solution (0 < I ≤ 1 mol L^− 1) and at t = 25 °C. The formation of two hydrolytic species VO(OH)⁺ and VO₂(OH)₂²⁺ and one complex with sulfate was found, with log β = − 5.65 for the reaction VO²⁺ + H₂O = VO(OH)⁺ + H⁺, log β = − 7.02 for the reaction 2VO²⁺ + 2H₂O = (VO)₂(OH)₂²⁺ + 2H⁺ and log K = 1.73 for VOSO₄⁰ species (at I = 0.1 mol L^− 1 and t = 25 °C). For these species, using calorimetric data, ΔH and TΔS values were also obtained. By using the above values, interactions of VO²⁺ with acetate (ac), malonate (mal), succinate (suc), 1,2,3-propanetricarboxylate (tca) and 1,2,3,4-butanetetracarboxylate (btc) ligands were studied potentiometrically and spectrophotometrically. The formation of ML⁺, ML₂⁰ and MLOH⁰ for ac; ML⁰, MLH⁺, ML₂²⁻ and ML₂H⁻ for mal; ML⁰, MLH⁺ and MLOH⁻ for suc; ML⁻ and MLH⁰ for tca and ML²⁻, MLH⁻ and MLH₂⁰ for btc were found. Formation constants are reported at I = 0.1 mol L^− 1, together with SIT parameters for the dependence on ionic strength. By visible spectrophotometric measurements, λ_max and ε_max values for the relevant species in solution were determined.     

Determination of the Splitting of the 6a0 and 6b0 Bands of C-Hexadeuterobenzene in a Supersonic Jet

By using resonance-enhanced two-photon ionization, rotationally resolved spectra of the 6¹₀ band of ¹²C₆D₆ and (¹³C¹²C₅D₆ molecules have been obtained for the first time at a rotational temperature of 0.7 K in a pulsed supersonic beam. From the former, the values of B″ = 0.1573 ± 0.0008 cm⁻¹, B′ = 0.1508 ± 0.0008 cm⁻¹, and ξ′ = −0.412 ± 0.050 have been derived for rotational and Coriolis constants in the lower and upper levels of ¹²C₆D₆. Also, the spectra corresponding to ¹²C₆H₆ and ¹³C¹²C₅H₆ have been measured and the values B″ = 0.1892 ± 0.0008 cm⁻¹, B′ = 0.1815 ± 0.0008 cm⁻¹, and ξ′ = −0.586 ± 0.050 have been obtained for ¹²C₆H₆, in agreement with previous results. Rotational constants of ¹³C labeled benzene molecules have been geometrically deduced from the constants obtained. Experimental isotopic shifts of the vibronic origins of the 6a¹₀ and 6b¹₀ bands have been determined. There is agreement with previous ¹³C-benzene-h₆ data. The present results are −0.91 ± 0.05 and 3.09 ± 0.05 cm⁻¹ for ¹³C¹²C₅D₆ and −1.64 ± 0.05 and 2.64 ± 0.05 cm⁻¹ for ¹³C¹²C₅H₆. The splittings of vibrational modes 6b and 6a in the ¹B_2u state are 4.00 ± 0.10 cm⁻¹ for ¹³C¹²C₅D₆ and 4.28 ± 0.10 cm⁻¹ for ¹³C¹²C₅H₆.     

Non-Kramers ENDOR and ESEEM of the S = 2 Ferrous Ion of [Fe(II)EDTA]

We report here the first non-Kramers (NK) ESEEM and ENDOR study of a mononuclear NK center, presenting extensive parallel-mode ESEEM and ENDOR measurements on the S_t = 2 ferrous center of [Fe(II)ethylenediamine-N,N,N′,N′-tetraacetato]²⁻; [Fe(II)EDTA)]²⁻. The results disclose an anomalous equivalence of the experimental patterns produced by the two techniques. A simple theoretical treatment of the frequency-domain patterns expected for NK-ESEEM and NK-ENDOR rationalizes this correspondence and further suggests that the very observation of NK-ENDOR is the result of an unprecedentedly large hyperfine enhancement effect. The mixed nitrogen–carboxylato oxygen coordination of [Fe(II)EDTA]²⁻ models that of the protein-bound diiron centers, although with a higher coordination number. Analysis of the NK-ESEEM measurements yields the quadrupole parameters for the ¹⁴N ligands of [Fe(II)EDTA]²⁻, K = 1.16(1) MHz, 0 ≤ η ≤ 0.05, and the analysis indicates that the electronic zero-field splitting tetragonal axis lies along the N–N direction.     

Millimeter-wave spectrum of DCCCHO in the ground vibrational state

About 140 a- and b-type millimeter-wave transitions of propynal-d₁, DCCCHO, were measured in the ground vibrational state. The accurate rotational and centrifugal distortion constants were determined from the observed frequencies including the previous microwave measurements. Seven microwave transitions observed by infrared-microwave double resonance were also included in the analysis. The determined constants are A = 66778.016(12), B = 4463.8489(7), C = 4177.7950(7), Δ_J = 0.0015919(5), Δ_JK = −0.139214(13), Δ_K = 9.4328(18), δ_J = 0.0002885(4), δ_K = 0.03069(4), H_JK = −0.817(13) × 10⁻⁶, H_KJ = −9.62(4) × 10⁻⁶, H_K = 0.00255(8), h_J = 0.0047(3) × 10⁻⁶, in MHz.     

Optical Recognition of Anions by Ruthenium(II)-Bipyridine-Calix[4]Arene System

The two t-butylcalix[4]arene attached ruthenium(II)-bipyridine complexes (Rubc2 and Rubc3) has been synthesized and the anion recognition studies have been carried out using emission techniques. The binding of anions, which are sensed by the complexes, are studied by UV-visible and emission techniques. The complex Rubc2 recognizes the Cl^?, H₂PO₄ ^? and AcO^? anions. The complex Rubc3 recognizes the Br^? and AcO^? anions. The AcO^? quenches the emission intensity of both two complexes but the other anion increases the emission intensity of the complexes. The excited state lifetime and transient absorption studies were carried out the AcO^? facilitates non radiative pathway. The other anions stabilize the excited state and facilitate the radiative pathway.     

Growth of carbon nanotubes (CNTs) on metallic underlayers by diffusion plasma-enhanced chemical vapour deposition (DPECVD)

Here, we demonstrate the low-temperature (480–612 °C) synthesis of carbon nanotubes (CNTs) on different metallic underlayers (i.e., NiV, Ir, Ag, Pt, W, and Ta) using diffusion (dc) plasma-enhanced (~20 W, −600 V) chemical vapour deposition (DPECVD). The catalyst used is bi-layered Fe/Al and the feedstock used is a mixture of C₂H₂ and NH₃ (1:4). The crucial component is the diffusion of radical ions and hydrogen generated such as H₂/H⁺/H₂⁺/NH₃⁺/CH₂⁺/C₂H₂⁺ (which are confirmed by in-situ mass spectroscopy) from the nozzle, where it is inserted for most effective plasma diffusion between a substrate and a gas distributor.     

The ν5Band of HClO4

The high-resolution infrared spectrum of perchloric acid has been observed in the 700–750 cm⁻¹region using the infrared beamline at the MAX-I electron storage ring in Lund, Sweden. The spectrum displays extensive rotational structure due to a typeaband and is assigned to ν₅, the HO–ClO₃stretch. Approximately 1100 transitions in H³⁵ClO₄and ca. 300 in H³⁷ClO₄have been fitted using single subband analysis, generating constants for transitions having the sameK. The origin of H³⁵ClO₄K= 3tseries is found to be 726.9971(4) cm⁻¹. Rotationally resolved infrared line positions are now available for the identification of HClO₄in the atmosphere, which may be produced by the heterogeneous oxidation of chlorine containing species in the stratosphere.     

Determination of Backbone Angle ψ in Proteins Using a TROSY-Based α/β-HN(CO)CA-J Experiment

Transverse relaxation-optimized NMR experiment (TROSY) for the measurement of three-bond scalar coupling constant between ¹H^α_i−1 and ¹⁵N_i defining the dihedral angle ψ is described. The triple-spin-state-selective experiment allows measurement of ³J_H^αN from ¹³C^α, ¹⁵N, and ¹H^N correlation spectra H₂O with minimum resonance overlap. Transverse relaxation of ¹³C^α spin is minimized by using spin-state-selective filtering and by acquiring a signal longer in ¹⁵N-dimension in a manner of semi-constant-time TROSY evolution. The ³J_H^αN values obtained with the proposed α/β-HN(CO)CA-J TROSY scheme are in good agreement with the values measured earlier from ubiquitin in D₂O using the HCACO[N] experiment.     

Rotational absorption spectrum of methylene fluoride in the 20–100 cm region

The pure rotational spectrum of CH₂F₂ was recorded in the 20–100 cm⁻¹ spectral range and analyzed to obtain rotation and centrifugal distortion constants. Analysis of the data yielded rotation constants: A = 1.6392173 ± 0.0000015, B = 0.3537342 ± 0.00000033, C = 0.3085387 ± 0.00000027, τ_aaaa = −(7.64 ± 0.46) × 10⁻⁵, τ_bbbb = −(2.076 ± 0.016) × 10⁻⁶, τ_cccc = −(9.29 ± 0.12) × 10⁻⁷, T₁ = (4.89 ± 0.20) × 10⁻⁶, and T₂ = −(1.281 ± 0.016) × 10⁻⁶cm⁻¹.     

Line strength measurements of carbonyl sulfide (OCS) in the 2v3, v1+2v2+v3, and 4v2+v3 bands

To support planetary studies of the Venus atmosphere, we measured line strengths of the 2v₃, v₁+2v₂+v₃, and 4v₂+v₃ bands of the primary isotopologue of carbonyl sulfide (¹⁶O¹²C³²S), whose band centers are located at 4101.387, 3937.427, and 4141.212 cm⁻¹, respectively. For this, infrared absorption spectra in normal carbonyl sulfide (OCS) sample gas were recorded at an unapodized resolution of 0.0033 cm⁻¹ at ambient room temperatures using a Bruker Fourier transform spectrometer (FTS) at the Jet Propulsion Laboratory. The FTS instrumental line shape (ILS) function was investigated, which revealed no significant instrumental line broadening or distortions. Various custom-made short cells and a multi-pass White cell were employed to achieve optical densities sufficient to observe the strong 2v₃ and the weaker bands in the region. Gas sample impurities and the isotopic abundances were determined from mass spectrum analysis. Line strengths were retrieved spectrum by spectrum using a non-linear curve fitting algorithm adopting a standard Voigt line profile, from which Herman–Wallis factors were derived for the three bands. The band strengths of 2v₃, v₁+2v₂+v₃, and 4v₂+v₃ of ¹⁶O¹²C³²S (normalized at 100% of isotopologue) are observed to be 6.315(13)×10⁻¹⁹, 1.570(2)×10⁻²⁰, and 7.949(20)×10⁻²¹ cm⁻¹/molecule cm⁻², respectively, at 296 K. These results are compared with earlier measurements and the HITRAN 2004 database.     

Hidden chemistry in phenoxyl radical (C6H5O•) coupling reaction mechanism revealed

A novel hidden reaction of the phenoxyl radical (C₆H₅O^?) with a specific daughter is found to significantly alter its hitherto accepted coupling reactions' scheme. Transient characterizations and mechanistic evaluations in highly acidic to strongly alkaline aqueous medium reveal this concurrent reaction competing favorably in nanosecond–microsecond time‐scale with the five distinct C₆H₅O^? + C₆H₅O^? reactions, which produce various phenolic end‐products as reported earlier (M. Ye and R. H. Schuler, J. Phys. Chem. 1989, 93, 1898). Presently, only the symmetric 4,4′‐dioxo transient precursor, O?C₆H₅? H₅C₆?O that leads to the stable 4,4′‐biphenol product, gets partially oxidized by a fraction of remaining C₆H₅O^?. The resulting secondary transient ^?C₁₂H₉O₂ radical is generated at diffusion‐controlled rate, k > 5.0 × 10⁹ M^?1 s^?1, and follows an independent chemistry. Consequently, when the previously reported five coupled end product distribution ratios were appropriately updated, the respective fractional values revealed a closer match for the symmetric 2,2′‐ and 4,4′‐biphenols with their suggested coupling reaction branching probabilities based on the atomic spin‐density distributions in the C₆H₅O^? radical (P. Neta, R. W. Fessenden, J. Phys. Chem., 1974, 78, 523). Results also suggest that in the remaining fraction, differential solvation in aqueous medium of various orientation‐related encounter complexes (C₆H₅O…C₆H₅O) formed during coupling favors rearrangement only toward 2,4′‐biphenolic product, at the cost of 2‐ and 4‐phenoxyphenolic species. Copyright © 2009 John Wiley & Sons, Ltd.     

Spectral characterization and energy levels of Cr:Sc2(MoO4)3 crystal

This paper reports the spectral properties and energy levels of Cr³⁺:Sc₂(MoO₄)₃ crystal. The crystal field strength Dq, Racah parameter B and C were calculated to be 1408 cm⁻¹, 608 cm⁻¹ and 3054 cm⁻¹, respectively. The absorption cross sections σ_α of ⁴A₂→⁴T₁ and ⁴A₂→⁴T₂ transitions were 3.74×10⁻¹⁹ cm² at 499 nm and 3.21×10⁻¹⁹ cm² at 710 nm, respectively. The emission cross section σ_e was 375×10⁻²⁰ cm² at 880 nm. Cr³⁺:Sc₂(MoO₄)₃ crystal has a broad emission band with a broad FWHM of 176 nm (2179 cm⁻¹). Therefore, Cr³⁺:Sc₂(MoO₄)₃ crystal may be regarded as a potential tunable laser gain medium.     

UV excimer laser photochemistry of hybrid organometallic compounds of gallium

The gas phase ultraviolet (UV) excimer laser induced photolysis of the gallium-alkyls Ga(t-C₄H₉) _n ^– (CH₃)_3–n (n=0, 1, 2, 3) was studied, using photolysis wavelengths of 308, 248, and 193 nm. The photofragments Ga, GaH, and GaCH₃ were detected by laser ionization time-of-flight mass spectroscopy, while the hydrocarbon products CH₄, C₂H₆, HC(CH₃)₃ and H₂C=C(CH₃)₂ were identified using Fourier transform infrared (FTIR) spectroscopy. The formation of the GaH photofragment, and a high olefin-to-alkane product ratio, for Ga(t-C₄H₉)₂(CH₃) and Ga(t-C₄H₉)₃ are interpreted to indicate a -hydrogen elimination process. However, -hydrogen elimination only occurs after fission of the weakest Ga-C bond, thus no -hydride elimination is observed for Ga(t-C₄H₉)(CH₃)₂. Detection of C₂H₆ for Ga(CH₃)₃ and Ga(t-C₄H₉)(CH₃)₂, but not for Ga(t-C₄H₉)₂(CH₃), shows that under our experimental conditions the formation of ethane is as a result of the reductive elimination of the methyl groups, and is not due to the recombination of two free methyl radicals.     

Novel Peak Assignments of in VivoC MRS in Human Brain at 1.5 T

¹³C MRS studies at natural abundance and after intravenous 1-¹³C glucose infusion were performed on a 1.5-T clinical scanner in four subjects. Localization to the occipital cortex was achieved by a surface coil. In natural abundance spectra glucose C_3β,5β, myo-inositol, glutamate C_1,2,5, glutamine C_1,2,5, N-acetyl-aspartate C_1-4,C=O, creatine CH₂, CH₃, and C_C=N, taurine C_2,3, bicarbonate HCO⁻₃ were identified. After glucose infusion ¹³C enrichment of glucose C_1α,1β, glutamate C_1-4, glutamine C_1-4, aspartate C_2,3, N-acetyl-aspartate C_2,3, lactate C₃, alanine C₃, and HCO⁻₃ were observed. The observation of ¹³C enrichment of resonances resonating at >150 ppm is an extension of previously published studies and will provide a more precise determination of metabolic rates and substrate decarboxylation in human brain.     

Photophysical Properties of New Terbium (III) Organophosphonates

This paper reports on the synthesis, characterization and photophysical properties of the Tb³⁺ organophosphonates, TbH(O₃PR)₂, methylphosphonate (R=CH₃), ethylphosphonate (R=C₂H₅), propylphosphonate (R=C₃H₇), and phenylphosphonate (R=C₆H₅). The layered Tb³⁺ organophosphonates were characterized by X-ray diffraction, IR spectroscopy, TG and elemental analysis. The interlayer distances of the Tb³⁺ organophosphonates evaluated by the X-ray diffractogram were 9.50 Å for TbH(O₃PCH₃)₂, 12.18 Å for TbH(O₃PC₂H₅)₂, 14.84 Å for TbH(O₃PC₃H₇)₂ and 15.20 Å for TbH(O₃PC₆H₅)₂. The Tb³⁺ luminescence data revealed highly green emissive materials when they were excited at 368 nm, where the characteristic ⁵D₄ → ⁷F _J (J=6, 5, 4 and 3) transitions of Tb³⁺ were observed at 488, 543, 585 and 619 nm, respectively. The lifetime of the Tb^{3+ 5}D₄ → ⁷F₅ transition (λ_exc=368 nm and λ_em=543 nm) for the Tb³⁺ organophosphonates was evaluated from the decay curves, which values were of 2.88, 2.22, 2.14 and 2.59 ms, respectively for TbH(O₃PCH₃)₂, TbH(O₃PC₂H₅)₂, TbH(O₃PC₃H₇)₂ and TbH(O₃PC₆H₅)₂. TG analysis revealed that these materials are thermally highly stable, with no water molecule in their composition, which makes them potential luminophores.     

High-resolution infrared spectra of HCF3 in the ν6 (500 cm) and 2ν6 (1000 cm) regions: rovibrational analysis and accurate determination of the ground state constants C0 and DK

The high-resolution infrared spectrum of HCF₃ was studied in the ν₆ fundamental (near 500 cm⁻¹) and in the 2ν₆ overtones (near 1000 cm⁻¹) regions. The present study reports on the analysis of the hot bands in the ν₆ region, as well as the first observation and assignment of the 2ν₆² perpendicular band. Using ν₆, 2ν₆^±2–ν₆^±1 and 2ν₆² experimental wavenumbers, accurate coefficients C₀ and D_K⁰ of the K-dependent ground-state energy terms were obtained, using the so-called “loop method.” Ground-state energy differences Δ(K,J)=E₀(K,J)−E₀(K−3,J) were obtained for K=3–30. A least-squares fit of 81 such differences gave the following results (in cm⁻¹): C₀=0.1892550(15); D_K⁰=2.779(26) × 10⁻⁷.     

Fourier Transform Spectroscopy of theYΣ–XΠiTransition of CuO

TheY²Σ⁺–X²Π_inear-infrared electronic transition of CuO was observed at high resolution for the first time. The spectrum was recorded with the Fourier transform spectrometer associated with the McMath–Pierce Solar Telescope at Kitt Peak. The excited CuO molecules were produced in a low pressure copper hollow cathode sputter with a slow flow of oxygen. Constants for theY²Σ⁺states of CuO are:T₀= 7715.47765(54) cm⁻¹,B= 0.4735780(28) cm⁻¹,D= 0.822(12) × 10⁻⁶cm⁻¹,H= 0.46(10) × 10⁻¹⁰cm⁻¹, γ = −0.089587(42) cm⁻¹, γ_D= 0.1272(79) × 10⁻⁶cm⁻¹,b_F= 0.12347(22) cm⁻¹, andc= 0.0550(74) cm⁻¹. ImprovedX²Π_iconstants are also presented.     

Positronium interactions with Cu(II) Ions in water

Summary Positronium reactions with Cu(II) ions in aqueous solution were investigated by measuring the concentration dependence of lifetime spectra and of 1D-ACAR curves for the following Cu (II) complexes: [Cu(H₂O)₆[²⁺, [Cu(NH₃)₄ (H₂O)₂]²⁺ and [Cu(EDTA)(H₂O)]²⁻. The combined analysis of lifetime and ACAR data shows that Cu(II) ions:a) reduce the formation of positronium (inhibition effect),b) promote both ortho ⇌ para conversion and redox reactions. It was also found that inhibition and reaction rate constants are affected by the ligand type.