Spectra Of Th Research Articles

Spectroscopy and structure of the simplest actinide bonds.

Understanding the influence of electrons in partially filled f- and d-orbitals on bonding and reactivity is a key issue for actinide chemistry. This question can be investigated by using a combination of well-defined experimental measurements and theoretical calculations. Gas phase spectroscopic data are particularly valuable for the evaluation of theoretical models. Consequently, the primary objectives of our research have been to obtain gas phase spectra for small actinide molecules. To complement the experimental effort, we are investigating the potential for using relativistic ab initio calculations and semiempirical models to predict and interpret the electronic energy level patterns for f-element compounds. Multiple resonance spectroscopy and jet cooling techniques have been used to unravel the complex electronic spectra of Th and U compounds. Recent results for fluorides, sulfides, and nitrides are discussed.

Kinetics of Reduction of Thionine with Ribose and the Structural Properties of the Dye at Different pH Using DFT Method

The reaction between the thionine (Th) and the ribose was observed spectrophotometrically and changes in absorbance of Th were recorded at variable concentration of dye, reductant and pH. A pseudo first order rate of reaction was found to establish the reduction kinetics of the dye, studied at a pH range of 0.34 to 12.8. Absorption spectrum of Th at different pH, with ribose showed a pH (12.8) dependent introversion. The reduction most probably took place with enediol intermediate of the sugar at high pH. A full geometry optimization of predominant species of Th namely, mono-deprotonated, di-deprotonated Th, and LTh (leuco thionine) respectively, at low and high pH, was performed at B3LYP level of theory. The data obtained from the energy minimization were in excellent agreement with other experimental and theoretical observations. The calculated enthalpies of formation for both reduction reactions (mono-deprotonated Th+H+→leucothionine and di-deprotonated Th+2H+→leucothionine) provided evidences for maximum reduction of the dye at high pH.

High-resolution visible spectroscopy of the jet-driving star Th 28

Context. We present a study of the extreme T Tauri star Th 28, a young stellar object in the Lupus 3 cloud whose spectrum displays all the varieties of signposts associated with early stellar activity. Th 28 is the driving source of a fast jet, making it a very promising target to study the disk-jet connection. Aims. We try to identify and investigate the different structural components that contribute to the different emission lines in the spectrum of the Th 28 central source. Methods. We obtained high-resolution visible spectroscopy with the UVES spectrograph at the VLT, using the resolved profiles of both permitted and forbidden lines as tracers of gas with different kinematic and physical properties, complemented with other observations from the literature. Results. We identify four distinct structural components that contribute to the visible emission-line spectrum of Th 28. The first one, dominating most of the permitted and forbidden lines, is probably associated with the origin of the outflow that in the past produced the Herbig-Haro objects seen to the west of Th 28. The second one is an uncollimated stellar wind characterized by high excitation and temperature, as shown by the broad profile of the intense [OIII] lines. The third component, traced only by permitted lines, appears as a redshifted tail extending up to radial velocities of +450 km s −1 , which we attribute to magnetospheric accretion. From the latter

Rampant changes in5f5∕2and5f7∕2filling across the light and middle actinide metals: Electron energy-loss spectroscopy, many-electron atomic spectral calculations, and spin-orbit sum rule

We examine the branching ratio of the ${N}_{4,5}$ $(4d\ensuremath{\rightarrow}5f)$ spectra of Th, U, Np, Pu, Am, and Cm metals using electron energy-loss spectroscopy (EELS) in a transmission electron microscope, together with many-electron atomic spectral calculations and the spin-orbit sum rule. Our results show the following. (1) The actinide metals Pu, Am, and Cm exhibit intermediate coupling. (2) The intermediate coupling values for the $5f$ states as calculated using a many-electron atomic model are correct for the actinides; this being proven by our results for curium. (3) The EELS branching ratio is sensitive to the degree of $5f$ electron delocalization, which is illustrated by the transition from $LS$ to intermediate coupling between U and Pu.

Structure and Properties of the Thorium Vanadyl Tellurate, Th(VO2)2(TeO6)(H2O)2.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Structure and Properties of the Thorium Vanadyl Tellurate, Th(VO2)2(TeO6)(H2O)2

The hydrothermal reaction of Th(NO3)4.xH2O with V2O5 and H6TeO6 at 200 degrees C under autogenously generated pressure results in the formation of Th(VO2)2(TeO6)(H2O)2 as a pure phase. The single-crystal X-ray data indicate that Th(VO2)2(TeO6)(H2O)2 possesses a three-dimensional structure constructed from ThO9 tricapped trigonal prisms, VO5 distorted square pyramids, VO4 distorted tetrahedra, and TeO6 distorted octahedra. Both of the vanadium polyhedra contain VO2+ vanadyl units with two short V=O bond distances. The tellurate octahedron is tetragonally distorted and utilizes all of its oxygen atoms to bond to adjacent metal centers, sharing edges with ThO9 and VO5 units, and corners with two ThO9, one VO5, and two VO4 polyhedra. Crystallographic data: Th(VO2)2(TeO6)(H2O)2, orthorhombic, space group Pbca, a = 12.6921(7), b = 11.5593(7), c = 13.0950(8) A, Z = 8 (T = 193 K). The UV-vis diffuse reflectance spectrum of Th(VO2)2(TeO6)(H2O)2 shows vanadyl-based charge-transfer absorption features. Th(VO2)2(TeO6)(H2O)2 decomposes primarily to Th(VO3)4 when heated at 600 degrees C in air.

Analysis of Th(IV)-humate by XPS

The tetravalent actinide humate complexation was investigated for types of bonding between Th(IV) and humic acid. The Th(IV)-humate was prepared in solution, separated by ultrafiltration and analyzed by X-ray photoelectron spectroscopy (XPS). The stability of humic acid against X-ray induced degradation was verified by high-resolution XPS during long-term irradiation. The Th 4f7/2line of Th(IV)-humate can be fitted by one Gaussian-Lorentzian function, indicating that one type of bonding is mainly involved in the complexation. The Th 4f spectrum of Th(IV)-humate is, as compared to those of other Th(IV)-compounds, similar to the Th(IV)-complex with an ion exchanger containing carboxylic functional groups only. The present XPS study corroborates EXAFS results, according to which Th(IV) is predominantly bound to carboxylic groups of humic acid and demonstrates the applicability of the XPS technique for the characterization of metal-humate complexes.

Semiempirical molecular orbital calculations on the prototropic tautomerism of 2-thiocytosine

Optimized geometries for the six tautomeric forms of 2-thiocytosine (TH) were obtained using the mopac program. The semiempirical MNDO molecular orbital (MO) method was applied to derive the localized MO, atomic charges, bond orders, vibrational spectra and thermodynamic properties in the range 100–500 K. The results show that the TH(7,8,8) and TH(1,8,8) tautomers are the predominant species at room and low temperatures, whereas at high temperatures the TH (1,7,8) tautomer could become important. The calculated IR spectrum of TH(1,8,8) fits the experimental bands well and a complete assignment based on the absolute energy contribution of each pair of bonded atoms and the radial motion is given.

Green's-function calculations of 5s-5p x-ray photoemission spectra of Ra (Z=88) and Th (Z=90).

The 5s-5p x-ray photoemission (XPS) spectra of metallic Ra (Z=88) and Th (Z=90) are calculated using a one-particle Green's function within nonrelativistic Hartree-Fock theory. The results for the 5s-5p region of the actinides show strong 5${s}^{\mathrm{\ensuremath{-}}1}$\ensuremath{\leftrightarrows}5${p}^{\mathrm{\ensuremath{-}}1}$5${d}^{\mathrm{\ensuremath{-}}1}$5(m)f [5${p}^{\mathrm{\ensuremath{-}}1}$\ensuremath{\leftrightarrows}5${d}^{\mathrm{\ensuremath{-}}2}$5(m)f] (m represents discrete and continuum) super-Coster-Kronig processes. The major features except the fine structure in the 5p XPS spectrum of Th are rather well described by the present calculations. To describe the fine structure, it is necessary to take into account the multiplet levels.

Spectroscopic Investigation of U(DBM) 4 U(TFBA) 4, Th(DBM) 4:U(IV), Th(TFBA) 4:U(IV) single crystals (DBM = 1,4-dibenzoyl-1,3-butane dione, TFBA = 4,4,4-trifluoro-1-phenyl-1,3-butane dione)

Single crystals of U or Th(DBM) 4-solvate, U or Th(TFBA) 4 and Th(DBM) 4-solvate or Th(TFBA) 4 doped with U(IV), few tenths of cubic millimeters in size, have been grown at low temperature from benzene (DBM) or toluene (TFBA) solutions. Other conditions do not lead to so large single crystals. All tetrakis-dibenzoylmethanato crystals exchange benzene molecules giving solvate crystals. They only can be kept unchanged in benzene saturated atomsphere. The yet unknown structure of these solvates are slightly different from the known ‘dry’ orthorhombic U(DBM) 4 (Pccn) [1, 2]. First investigation on U(DMB) 4 solvate essentially shows a 15% increasing of the b parameter and a 20% increasing of the orthorhombic volume cell. Space group is Pcbb. This probably means that benzene molecules insert themselves between the U(DBM) 4 layers of the dry crystals. In both structures, U lies on a C 2 crystallographic axis parallel to z. The structure of the tetrakis-trifluorobenzoylmethanato crystals is known to be tetragonal (I4 1/a) [3]. Polarized high resolution spectra of all these single crystals have been obtained between 4000 and 20000 Å in the temperature range 4−300 K, Some common features appear on these spectra. The thorium chelates show two bands. The Th(DBM) 4:U(IV) and Th(TFBA) 4:U(IV) which are the best resolved spectra among all the recorded ones, show about thirty vibronic bands, some of them having a width of 10 Å at 4 K. A quite god polarization of Th(DBM) 4:U(IV) spectra is surprising for such an orthorhombic lattice. This means that probably the two optical axes are so close together that the crystal appears at 4 K as uniaxial. The 4 K polarized spectra look like very accurately the σ and π U 4+ spectra in β-ThBr 4 and β-ThCl 4 matrix or UCl 4, all of them being uniaxial tetragonal crystals [4, 5] where point group symmetry of U 4+ in D 2d. So, point group symmetry of U(IV) is close to D 2d or another group whose characteristic table is the same. These observations cannot be explained according to the above mentioned insertion of benzene molecules without any other changes in the positions of U in the lattice. In dry U(DBM) 4, point group symmetry of U(IV) is D 4d or C 2 depending on whether the considered environment is a square antiprism of oxygen or the whole molecule. Spectra of Th(DBM) 4:U(IV) have temporarily assigned on the D 2d basis point group symmetry. Broadness of the lines leads to poorly significant values of the F k and B k q parameters. As expected for a tetragonal crystal and a S 4 point group symmetry for U(IV), polarization of Th(TFBA) 4:U(IV) is found and spectra of U(IV) are very different from those of D 2d symmetry. σ lines are more numerous than π lines and this could indicate according to dipole selection rules for S 4, that ground state is two fold degenerate. Unfortunately no spectra of U(IV) have today been assigned in a such symmetry. The spectra we have recorded could be a basis calculations.

Electron transfer in the quenching of protonated triplet thionine and methylene blue by ground state thionine

The quenching of the monoprotonated lowest triplet state of thionine ( 3TH 2 2+) by ground state thionine (TH +) was investigated by laser flash photolysis—kinetic spectrophotometry employing frequency-doubled (347.2 nm) flashes from a Q-switched ruby laser. The quenching of the monoprotonated lowest triplet state of methylene blue ( 3MBH 2+) by TH + was similarly investigated using the fundamental (694.3 nm) ruby frequency. In 0.01 M acid the quenching of 3TH 2 2+ by TH + is accompanied by net electron transfer to give the semi-oxidized radical (TH 2 + ) and the semi-reduced radical (TH 2 + ) while the quenching of 3MBH 2+ by TH + is accompanied by the net one-electron oxidation of 3MBH 2+ by TH + to give MB 2 + and TH 2 +. Spectra of TH 2 + and TH 2 + in water, 50 vol.% aqueous CH 3CN and 50 vol.% aqueous C 2H 5OH in the presence of 0.01 M acid were characterized. The dependence of the specific rate k q of quenching and the specific rate k et of net electron transfer for the quenching of 3TH 2 2+ by TH + on the solvent composition, the nature of the anions and the salt concentration was investigated. The efficiency F 1 (= k et/ k q) of net electron transfer in the quenching of 3TH 2 2+ by TH + correlates with Kosower's solvent polarity parameter Z as it does in the quenching of 3MBH 2+ by a reversible electron transfer mechanism, namely ln[1/ F 1) — 1∼ varies linearly with Z. Values of k q and k et for the quenching of 3MBH 2+ by TH + are similar to those for the quenching of 3MBH 2+ by ground state methylene blue (MB +) and about one-tenth of those for the quenching of 3TH 2 2+ by TH + in the same media. Values of F 1 for the quenching of 3TH 2 2+ by TH + differ little from those for the quenching of 3MBH 2+ by MB + in the same media except that increased salt concentration sharply reduces F 1 in the former case and does not significantly affect it in the latter. Values of F 1 for the quenching of 3MBH 2+ by TH + are substantially lower than for the homogeneous cases. The mechanism of crossed and homogeneous ground state quenching and the implications of ground state quenching for the efficiency of Fe—thiazine photogalvanic cells are discussed.

Far IR spectra of Th(IV) halide complexes of some heterocyclic bases

Far IR spectra of Th(IV) halide complexes of some heterocyclic bases

Recent developments in appearance potential spectroscopy

Appearance potential spectroscopy measures the probability for the creation of a hole in an inner atomic shell as a function of electron bombardment energy. The spectrum of excitation thresholds provides a simple means of examining the elemental composition in the surface region of a solid. Near threshold the excitation transitions indirectly probe the unoccupied conduction band states. The localized core state, however, overlaps only part of the conduction band, and the line shapes are thus related to a very local density of states. The interpretation is complicated by broadening introduced by the finite lifetime of the core hole, variations in the magnitude of the atomic matrix elements which suppress some thresholds, and the screening response of the conduction electrons to the suddenly altered core potential. These problems are illustrated by spectra of Th, Nb, Re, SC 2O 3, Ni, and Si surfaces. Distinct spectral characteristics related to crystallographic orientation are reported for nickel single crystals.

STRUCTURE AND CONFORMATION OF Th(IV)-COMPLEXES OF TRIETHYLENETETRAMINEHEXAACETIC ACID IN AQUEOUS SOLUTION

Abstract The aqueous (D2O) infrared and proton nmr spectra of triethylenetetraminehexaacetic (TTHA) and the 1 : 1 Th(IV)[sbnd]TTHA chelate have been studied as a function of “a” value (a = moles of base/mole of ligand). With the aid of infrared and nmr data the specific successive protonation sites of the anion are described as a function of increasing hydrogen ion concentration. The nmr spectra of Th(IV)[sbnd]TTHA indicate that with increasing alkalinity protonated species persist until a = 4 (pD 1.47), where an extremely stable [Th(IV)[sbnd]TTHA]2− chelate predominates. The nmr spectra of the Th(IV)[sbnd]TTHA complex at a = 6 exhibit characteristic multiplet splitting patterns for the ligand geminal acetate protons, indicating environmental non-equivalence of the ligand atoms. A ten-coordinate Th(IV) complex is proposed for Th(IV)[sbnd]TTHA. Certain acetate protons in the Th(IV)[sbnd]TTHA chelate undergo stereospecific deuteration in alkaline D2O at 95°.

Proton Magnetic Resonance Solvation Study of Sc(NO3)3, Y(NO3)3, and Th(NO3)4 in Water–Acetone Mixtures

Cation coordination measurements of Sc(NO3)3, Y(NO3)3, and Th(NO3)4 in water–acetone mixtures have been made by a proton magnetic resonance method. At low temperatures, solutions of these salts exhibit separate proton resonance signals for bulk water and water molecules in the primary solvation shell of the cation. Integration of these signals provides a direct measure of the number of water molecules coordinated to the cation. Values of 3.9, 2.4, and 2.9 were obtained for Sc(III), Y(III), and Th(IV), respectively, over a range of salt and solvent concentrations. These values may reflect extensive ion pairing in these solutions, particularly in the Y(III) and Th(IV) cases. The PMR spectra of Th(IV) solutions revealed multiple signals for the protons of coordinated water molecules, lending evidence to the postulate of ion pairing in these systems.

Low even configurations in the first spectrum of thorium (Th I)

Positions of twenty-one observed levels in the 6 d 2 7 s 2 and 6 d 3 7 s configurations of Th I are calculated with a mean error of ±143 cm -1, by use of seven adjustable parameters. This mean error is reduced to ±47 cm -1 by use of the L( L+1) correction in a calculation with eleven adjustable parameters. The agreement between observed and calculated g-values is satisfactory. The parameters are compared with ones already published for related configurations in the spectra of Th II and Th III. With one exception, similarly defined parameters show a roughly linear variation with the degree of ionization, in accordance with simple expectation. The effect of neglecting the 6 d 4 configuration in Th I is briefly discussed to explain this exception.

β-ray spectroscopy in the precision range of 1 : 10 5

An iron-free double focusing β spectrometer for precision work is described. Several conversion lines in the spectrum of Th B + C have been measured absolutely, using a method which eliminates the measurement of the magnetic field. By combining several such β spectroscopic data one can caculate the elementary constant combination h/ m 0 c. The result is in excellent agreement with results obtained by other means. This is a sensitive check on the accuracy of the individual B ϱ values of the different lines.

β-Ray spectroscopy in the precision range of 1 : 10 5

An iron-free double focusing β spectrometer for precision work is described. Several conversion lines in the spectrum of Th B + C have been measured absolutely, using a method which eliminates the measurement of the magnetic field. By combining several such β spectroscopic data one can caculate the elementary constant combination h/m 0c . The result is in excellent agreement with results obtained by other means. This is a sensitive check on the accuracy of the individual Bϱ values of the different lines.

The3p3Σ→2s3Σ-Bands of TH andT2

The molecular spectra of TH and ${\mathrm{T}}_{2}$ were photographed under high dispersion. The classification of the $3{p}^{3}\ensuremath{\Sigma}\ensuremath{\rightarrow}2{s}^{3}\ensuremath{\Sigma}$-system is given for these two molecules as well as the molecular constants for the $3{p}^{3}\ensuremath{\Sigma}$-state. Irregularities in the structure including typical perturbations are accounted for by interaction with the $3{p}^{3}\ensuremath{\Pi}$-state. This system, with 58 known bands and more than 1150 classified lines, is now known considerably better for ${\mathrm{T}}_{2}$ than for any other species of hydrogen molecule, including ${\mathrm{H}}_{2}$.

The Molecular Spectrum of Hydrogen. The Fulcher Bands of TH andT2

The spectra of TH and ${\mathrm{T}}_{2}$ were photographed under high dispersion. The analysis of the $3p^{3}\ensuremath{\Pi}\ensuremath{\rightarrow}2s^{3}\ensuremath{\Sigma}$ bands of these molecules is presented and the constants of the two states given.