The dissociation energies of gaseous Br2 and I2

New rotational analyses have been made of the B³Π_0⁺u—X¹Σ⁺_g systems of ⁷⁹Br₂, ⁸¹Br₂ and ¹²⁷I₂. The density of vibrational states near the dissociation limit in the upper states follows the LeRoy—Bernstein predictions for n = 5. From short extrapolations, the ground state dissociation energies are found to be: D₀(⁷⁹Br⁸¹Br) = 15895.6 cm^?1, D₀(¹²⁷I₂) = 12440.1 cm^?1.     

PhI(OAc)2/I2 induced aziridination of alkenes with TsNH2 under mild conditions

The aziridination of alkenes with the direct use of p-toluenesulfonamide (TsNH₂) was achieved by using PhI(OAc)₂ and I₂ under mild conditions. The reaction affords aziridines in moderate to good yields, and offers good manipulability by avoiding the use of the expensive metal catalyst and the unstable and explosive PhINTs.     

Laser excited fluorescence of I2

The fluorescence spectrum of iodine was investigated from 200 to 520 nm in the presence and absence of buffer gases following excitation of I₂ with 193 nm photons. The pressure dependence of the fluorescence and tentative transition assignments for one new and several less well-known I₂ emission bands are discussed.     

Competition between reactive and inelastic processes involving I2(D1Σ+u)

The removal of I₂(D¹Σ⁺_u) by CH₃Cl, following optical excitation at 193 and 185 nm has been studied by monitoring flourescence throughout the region 200–500 nm. It is observed that quenching of this state occurs both by reaction to form CH₃I and CH₂ClI and by inelastic collisions to the lowest ion-pair state (³Π_2g).     

Rate of the reaction I2 + F2 → products

The rate coefficient, k1, for the reaction I2+F2k1→ products has been measured at room temperature to be k1 = (1.9 = 0.4) × 10?15 cm3/molecule s. The macroscopic rate is compared to microscopic cross-section data obtained from molecular beam experiments and is found to be consistent with the bimolecular reaction I2 + F2→ I2F + F.DG|National Research Council/Resident Research Associate.     

Angular momentum polarization in molecular beams of I2 and Na2

The degree of molecular alignment, due to nozzle expansion, has been determined in supersonic beams of I₂ and Na₂, using the technique of laser-induced fluorescence. It is found that the anisotropic distribution of angular momenta is of the form 1 + ₂P₂(cos ). The alignment appears to be small for I₂ while for Na₂ a considerably larger effect is measured. Two internal states are studied, v = 0, J = 28 and v = 3, J = 43; both under various source conditions. It is found that the alignment depends on the internal state of the molecule and for each state can be described as a unique function of pd, the product of source pressure and nozzle diameter. The results are explained using a moel based on scattering between atoms and dimers with different velocity distributions. It is suggested that alignment may be a general feature in seeded molecular beams containing nonspherical components.     

Depth profiles of Ta2O5/SiO2/Si structures: a combined X-ray photoemission, Auger electron, and secondary ion mass spectroscopic study

Summary We prepared thin films of tantalum oxide on SiO₂/Si substrates by thermal oxidation of tantalum. The different oxide layers and their interfaces were characterized by SIMS, AES, and XPS. Characteristic structures were obtained after different oxidation procedures. The comparative discussion of AES and SIMS depth profiles makes possible an unequivocal characterization of the reactive interfaces between the oxides of Ta and Si. The Ta₂O₅/SiO₂ interface in particular shows non-stoichiometries which depend on the oxidation procedures and which determine the performance characteristics of pH-sensitive Ta₂O₅ field-effect transistors.

---

Tiefenprofile von Ta₂O₃/SiO₂/Si-Strukturen: Eine kombinierte Untersuchung mit Röntgen-Photoemissions-, Auger-Elektronen- und Sekundär-Ionen-Massen-Spektrometrie

     

High-resolution Auger electron spectroscopy of phase boundaries in TiC/TiB2 materials

Summary Multi-phase hard materials free from binder metals are used to meet the requirements of high wear resistance and high temperature stability. Investigations of properties and wear behavior showed extremely high values in carbide/boride combinations, particularly a TiC/TiB₂ mixture of a 11 molar ratio. The pseudobinary phase diagram shows low intersolubilities. High-resolution Auger Electron Spectroscopy was used to examine mixed two-phase TiC/ TiB₂ hard materials and compare them to pure TiC and TiB₂. The AES analyses were carried out on cross sections and fresh fracture surfaces. At the grain boundaries in pure TiC as well as in pure TiB₂, some amounts of Fe, Cr, Co and P can be detected. These elements are already in the powders as received. In addition, an O-rich phase has been identified in hot pressed TiB₂. The same impurity elements as in the pure materials can be found at a few phase boundaries and triple points in two-phase TiC/TiB₂ with a thickness of a few monolayers. However, large areas of the fracture surface were found to carry a TiB_xC_y phase on the grains. The considerable increase in wear resistance and fracture toughness of TiC/TiB₂ compared to pure TiC and pure TiB₂ can be explained by the presence of this TiB_xC_y phase.

---

Grenzflächenuntersuchungen an TiC/TiB₂-Hartstoffen mit hochauflösender Auger-Elektronenspektroskopie

     

Reductive carbonylation of nitrobenzene over Pd/Fe/I2/Py and Pd/C/Fe/I2/Py catalytic systems

A simple catalytic system containing metallic palladium, iron and iodine has been shown to be very active in the carbonylation of nitrobenzene to carbamate. The influence of the components of the catalytic system studied on its selectivity and activity has been established. It has been found that the catalytic activity of palladium supported on carbon (using both lignite coal and bituminous coal) was not lower than the activity of metallic palladium. This revised version was published online in August 2006 with corrections to the Cover Date.     

Molecular beam chemiluminescence. Three-body processes in the micro-torr region: The Ba + X2(Cl2, Br2, I2) → BaX*2 reactions

The intensity of the chemiluminescence continua from the title reactions was measured in crossed effusive molecular beams as a function of halogen beam flux. The dominant quadratic pressure dependence of the Ba + Cl₂, Br₂, I₂ reactions at halogen densities as low as ≈ 10¹¹ molecules/cm³ indicates a three-body process (rapid collissional stabilization of a very long-lived collision complex) as the major mode of MX^*₂ formation, while a two-body process is discernible at the lowest X₂ gas densities. The mechanism is discussed in some detail.     

Beam-gas chemiluminescent reactions of Cu(2D) with Cl2, Br2, and I2

Chemiluminescent reactions involving copper and halogen molecules are shown to result from the bimolecular reaction of metastable Cu(²D) with Cl₂, Br₂, and I₂ under single-collision conditions. The collision-energy dependence of the reactions is described by a hard-sphere model with zero threshold energy. Cross sections for these reactions are compared with that for chemiluminescent reaction of Cu(²S) with F₂.     

The vibrational relaxation of I2 by H2 in a supersonic jet

The vibrational relaxation of I₂ by H₂ has been studied in a supersonic free jet. It was observed that the addition of 5% H₂ to the helium carrier gas greatly reduces the concentration of X ¹Σ⁺_g(ν″ = 1) I₂ in the jet as compared to the concentration in a pure helium carrier. From this observation we have determined that the average vibrational relaxation cross sections of H₂ is 7.1 times as large as that of helium. Since the average vibrational relaxation cross section of deuterium is at least as large as that of hydrogen, the mechanism responsible for this phenomenon appears not to be dominated by mass effects.     

双介孔结构的纳米TiO2/I2复合材料的制备及其可见光催化性能

以钛酸丁酯为前驱体, 碘溶胶为碘源, 在室温下采用水解沉淀法制备了单质碘和纳米TiO₂复合的双介孔结构光催化剂(M-I₂-TiO₂). 采用X射线衍射(XRD)、透射电子显微镜(TEM)、比表面分析(BET)、紫外-可见(UV-Vis)漫反射光谱和傅里叶变换-红外光谱(FT-IR)对M-I₂-TiO₂进行了表征. 以次甲基蓝(MB)溶液为模拟废水, 对M-I₂-TiO₂的光催化性能进行了评价, 研究了不同热处理温度对光催化活性的影响. 结果表明, M-I₂-TiO₂在可见光区有显著的吸收, 300 ℃热处理得到的样品比表面积高达227.6 m²/g, 600 ℃热处理所得样品的比表面积仍高达111.8 m²/g, 而400 ℃热处理所得样品具有最好的光催化降解性能. 双介孔结构纳米TiO₂/I₂复合材料的光催化降解性能显著高于相同方法制备的纯TiO₂和Degussa P-25商业产品. 催化剂经6次重复使用其光催化活性基本保持不变.     

A 340 nm emission system in I2 induced by a two-photon excitation process

Iodine vapour is optically excited in a two-step process populating selectively the first four vibrational levels of an ion-pair state having T_e = 47032 ± 6 cm^?1 and ω_e = 98 ± 2 cm^?1. Fluorescence from this state is observed at 340 nm with vibrational resolution and is found to terminate on levels of the intermediate B state.     

Preparation et structure cristalline de I0.33NbSe4(I4Nb12Se48)

Single crystals with I_0.33NbSe₄ composition are grown, along with NbSe₂ crystals, by iodine vapor transport from NbSe₃. Single phase powder is obtained by heating the elements in corresponding proportions at 700°C. The structure has been studied by X-ray diffraction on a single crystal. The symmetry is tetragonal with the following parameters of the unit cell a = 9.489 Å, c = 19.13 Å. The space group is $\text{P4}\text{mnc}$ with Z = 12. The structure is built up with chains of rectangular [NbSe₈]-antiprisms. Iodine atoms are located between these chains.     

Determination of diffusion induced concentration profiles in Cr2O3 films on ceramic Al2O3 by Auger sputter depth profiling

Annealing induced interface and bulk effects in thin Cr₂O₃ films on aluminum oxide have been studied. The investigated samples have been prepared by reactive r.f. magnetron sputter deposition of Cr₂O₃ on ceramic Al₂O₃ substrates. Annealing at temperatures up to 1250° C have been carried out in situ under ultra high vacuum. Temperature induced compositional changes have been subsequently determined by AES sputter depth profiling without breaking the vacuum. The non-conducting substrates and the overlap of the Cr-(LMM)- and O-(KLL)-Auger peaks required special analysis parameters and spectra interpretation to obtain the concentration depth profiles of the different elements (Al, O, Cr).     

An approximate potential energy surface for HeI2 collisions

We have calculated the interaction potential for HeI₂ in T-shaped geometries using Hartree—Fock and Møller—Plesset third-order perturbation t     

Isomerization of 1,2-diiodoethylene in a laser-induced chemical reaction of I2 + C2H2

A laser-induced chemical reaction of I₂ + C₂H₂ has been studied and the formation of cis and tians isomers of 1,2-diiodoethylene has been observed. The ratio of the two isomers of 1,2-diodoethylene changes markedly upon changing the laser wavelengths of excitation of the I₂ molecule     

PPh3/I2/HCOOH: An efficient CO source for the synthesis of phthalimides

A straightforward and general method has been developed for the synthesis of phthalimide derivatives from 2-iodobenzamides and PPh₃/I₂/HCOOH in the presence of a catalytic amount of Pd(OAc)₂. The reaction results demonstrate that PPh₃/I₂/HCOOH is a facile, efficient and safe CO source. The whole process is carried out in toluene at 80?°C and furnishes the desired products in good to excellent yields.