CO adsorption on clean and oxidized Al(110)

Electron-energy loss (EELS) spectra and thermal desorption (TDS) traces of carbon monoxide bound to the (100) surface of aluminum are presented. CO chemisorption on clean Al(100) is characterized by vibrational bands at 440 and 2060 cm⁻¹ and by desorption at 125 K. Oxide “islands”, formed by oxidation in O₂ at 575 K, have no observed electronic influence on open metallic areas of the adsorbent but merely block CO adsorption sites.     

Metal complexes of 1,4,10-trioxa-7,13 -diazacyclopentadecane-N,N'-diacetic acid

The cyclic diaza-crown ether complexone cTOPDA (1,4,10-trioxa-7,13-diaza- cyclopentadecane-N,N'-diacetic acid) has been synthesized and characterized by elemental analysis, titration and NMR spectroscopy. Its ionization constants and the stability constants of its ML and M₂L complexes formed with alkali, alkaline-earth and some transition and representative metals were determined at 25.0±0.1°C and ionic strength 0.10 M (Me₄NNO₃). This ligand forms considerably more stable complexes with the transition metals than the analogous tetraoxa-diaza crown ether complexone cTOODA (1,4,10,13- tetraoxa-7,16-diazacyclooctadecane-N,N'-diacetic acid), but this last ligand favours ions with larger size, particularly K⁺. The cobalt(II) complex of cTOPDA is more stable than the nickel(II) complex, hence the Irving-Williams' order of stability is not obeyed for its transition-metal complexes. These effects are discussed in terms of the size of the cavity of the ligand and of the stereochemical constraints that it may impose.     

π* ← n electronic absorption spectrum of 2,6-dichloropyrazine

The π* ← n electronic absorption system of 2,6-dichloropyrazine, corresponding to the ¹B_3u ← ¹A_1g transition of pyrazine, has been recorded in the vapour phase and in solution in cyclohexane. A vibrational analysis of this system has been proposed and it is shown that vibronic interaction between two excited states of 2,6-dichloropyrazine exists. Another system is observed in the solution spectrum of this molecule in cyclohexane and it is shown to be a π* ← π transition analogous to the ¹B_2u ← ¹A_1g transition in pyrazine.     

Synchronous wavelength scanning room temperature phosphorescence: Comparison of cyclodextrin and micellar media

Application of synchronous wavelength scanning to two fluid phase room temperature phosphorescence (RTP) techniques using β-cyclodextrin and micelles are evaluated and compared. The selectivity, sensitivity, susceptibility to light scattering interference and classes of compounds amenable to determination by the two RTP approaches are discussed. Synchronous wavelength scanning cyclodextrin RTP studies focus on its usefulness for identification of nitrogen heterocyclic phosphors. Spectral resolution is improved in both RTP techniques by second derivative manipulation of the digitally stored synchronous spectra. A significant scatter interference resulting from turbidity produced by the cyclodextrin inclusion complexes imposes constraints on the selectivity and sensitivity achievable with the cyclodextrin medium, especially when using synchronous wavelength scanning. Generally, micelle-induced RTP was found to be superior to cyclodextrin-induced RTP for analysis of various mixtures of the 12 heterocyclics and 15 carbocyclics studied, as well as for a mixture of the drug, propranolol, and its 4-hydroxy metabolite.     

Renormalisation properties of the self-interactions of a massive vector superfield

We show by explicit computation that the requirement of one-loop on-shell renormalisability restricts the self-couplings of one massive vector superfield to those coming from a spontaneously broken U(1) gauge theory.     

A preliminary study on the dielectric constant of WPC based on some tropical woods

The use of WPC as an important insulating material is studied by determining its dielectric constant. The variation of dielectric constant with moisture content is also investigated. Preliminary results show that all untreated woods studied have a higher dielectric constant than their polymer composites with the exception of Kapur and Keruing. It is therefore postulated that the presence of polymers has led to a decrease in the number of polarizable units. Such a material may be useful commercially.     

Low-energy antiproton-neon interaction

By means of a streamer chamber exposed to the LEAR antiproton beams, the total reaction cross sections, the charged-prong multiplicity distributions and lower limits for the production of negative pions and K_s⁰ in the p̄-Ne interaction were measured at 19.6, 48.7 and 179.6 MeV. Annihilation was found to be dominant over all other non-elastic p̄-Ne processes. An analysis of Ne and other nuclei data in the frame of the Glauber theory allowed us to determine the ratio between the p̄-n and the p̄-p cross sections. An analysis in the light of INC model predictions allowed us to show up events which can be interpreted as annihilations having occurred deeply inside the nuclei.     

Pulsed μ− SR measurement of negative muon depolarization in muonic 13C and 14N

Slow depolarization rates of the upper hyperfine (HF) states (F⁺) of μ⁻¹³C and μ⁻¹⁴N were observed by means of the negative muon spin rotation method with a pulsed beam. The result for μ⁻¹³C agrees with the HF transition rates expected by Auger processes, while that for μ⁻¹⁴N is too high, suggesting a HF transition due to the intramolecular excitation effect.     

Compressed liquid densities of propane—normal butane mixtures between 10 and 60°C at pressures up to 9.6 MPa

Compressed liquid densities for propane—normal butane mixtures are reported at six temperatures between 10 and 60°C. For each isotherm, there are at least seven compositions ranging between 10 and 75 mol% propane at pressures from near saturation up to 9.65 MPa. The derived excess volumes are negative and represent a maximum of 0.5 percent of the mixture volume at 10°C. At 60°C, the excess volume can be up to 2.2% of the mixture volume. In addition to the binary data, limited density measurements were made on ternary mixtures containing up to 17 mol% ethane.