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Acaeruloplasminaemia is an autosomal recessive disorder affecting iron metabolism which results in diabetes, retinal degeneration and neurological disease. We previously reported the clinical and laboratory features of two brothers with absent serum caeruloplasmin and dementia. We now demonstrate that these two patients have a novel mutation in the caeruloplasmin gene. Definitive demonstration of a caeruloplasmin gene mutation in this family extends the clinical spectrum of this disease and suggests that acaeruloplasminaemia must be considered in the diagnostic evaluation of the inherited dementias. Although the precise mechanisms leading to dementia in this disease are unknown, these data may have broad implications for our understanding of the role of iron- and oxidant-mediated tissue injury in a variety of human neurodegenerative diseases.

Sintered discs (1450 °C) of yttria-stabilised tetragonal zirconia (3 mol% Y2O3) with additions of 1, 10 and 20 mol% TiO2, were treated in distilled water in an autoclave at 170 °C for times up to 144 h. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to monitor changes which occurred at the surface of the discs during autoclave treatment. The addition of TiO2 retarded the transformation of the tetragonal (t)-phase to monoclinic (m)-phase as determined by XRD. During autoclave treatment an increase in the Ti Zr ratio, decrease in the Y Zr ratio and a peak in the percentage Zr3+ were observed using XPS. Furthermore, at long autoclave treatment times there was a surface oxygen enrichment in excess of that expected from the stoichiometry. The data have been interpreted in terms of vacancy annealing and the rate of transformation to m-ZrO2 appears to be related to the presence of Zr3+, adsorbed water and substitutional cations such as Ti4+ in modifying adsorption sites at the surface.

Aluminium (Al) is an important structural engineering material, its usage ranking only behind ferrous alloys (Birbilis, Muster et al. 2011). The growth in usage and production of Al continues to increase (Davis 1999). The extensive use of Al lies in its strength:density ratio, toughness, and to some degree, its corrosion resistance. From a corrosion perspec‐ tive, which is most relevant to this chapter, Al has been a successful metal used in a num‐ ber of applications from commodity roles, to structural components of aircraft. A number of Al alloys can be satisfactorily deployed in environmental/atmospheric conditions in their conventional form, leaving the corrosion protection industry to focus on market needs in more demanding applications (such as those which require coating systems, for example, the aerospace industry).

Two series of α-Al2O3 seeded hydrous aluminas, unwashed (containing (NH4)2NO3) and washed, were examined by XPS and NMR after heat treatment. The unwashed material, which transforms to α-Al2O3 at 950°C, contained less AlO4 at all treatment temperatures up to the α-Al2O3 transition than the washed material; an explanation is given.

The scanning tunnelling microscope has been used to resolve the surface microstructure of natural galena (PbS), cleaved in air. Large atomically flat (001) planes with single and multiple atom layer steps are common. Cubic (100) facets and dislocations are observed. Surfaces exposed to air for several days have also been imaged and results are compared with oxide depth measurements by XPS. We present evidence for discontinuous oxide layers on these air-exposed surfaces, which may have some implications in the flotation chemistry of minerals of this type.

The binding energy of the Ar2p 3 2 level of Ar implanted into insulating oxides has been determined via Au calibration. The Ar2p 3 2 binding energy has been demonstrated to be constant at a binding energy of 242.3 ± 0.1 eV for a range of oxides including γ-Al2O3, ZrO2, SiO2 and Y2O3.

The potential of high-efficiency laser buried grid cells in CZ wafers is evaluated for use in concentrators up to 20 suns insolation. The standard one-sun cell shows acceptable efficiency up to seven times concentration. Simple modifications of the one-sun cell structure have been evaluated with measurements up to 12.6 suns. The best structure was optimized in its fabrication, and produced an efficiency of 18% (25 degrees C) and showed the potential to achieve 20% at 20 suns. >

The heat exchange method (HEM) process has been used to produce ingots up to 80 kg in weight. The minority carrier diffusion length of ingots has been measured principally by the time-resolved microwave reflectance technique to determine the factors limiting the diffusion length. Feedstock selection is important, but boron doping plays only a minor role. Intra-grain crystallographic defects appear to limit diffusion length strongly. Under optimized conditions a minority carrier diffusion length of 230 mu m at 1 Omega -cm resistivity has been achieved. Solar cell efficiencies of up to 12.7% have been achieved in production. >

Zirconia-based materials combine good thermomechanical properties and oxygen ion conductivity with chemical inertness and structural stability in a range of chemical environments. Polycrystalline materials, which are used in the bulk of applications, display a rich variety of segregation behaviour due to impurities which are invariably present either in the starting powders or inadvertently incorporated during processing. The mechanisms whereby, many, though not all, of these impurities and alloying components accumulate at the external or grain boundary interfaces are examined. The accumulation of impurities or components at the grain boundary can significantly change the grain boundary composition. Consequently, many of the macroscopic properties of these materials can depend critically on the chemistry of the grain boundary. An overview from both a thermodynamic and atomistic approach, of the development of the grain boundary network and the changing chemistry in the region of the grain boundary during the sintering process is presented. A qualitative appraisal of some current segregation and sintering theories are discussed. Surface analysis, by a variety of techniques, can probe the composition of interfaces within ZrO2-based ceramics giving valuable information of the distribution of impurities and components. A review of the contribution of surface analysis, particularly X-ray photoelectron spectroscopy, to the understanding of segregation phenomena and its effects on ceramic properties, is given. The review concentrates on Y2O3-ZrO2, CeO2-Y2O3-ZrO2 and Al2O3-Y2O3-ZrO2. The contribution of surface analysis to the understanding of low temperature degradation of yttria-tetragonal zirconia polycrystal is also examined.

We report two brothers with complete caeruloplasmin deficiency. The brothers presented with dementia and diabetes mellitus. Twelve relatives have partial caeruloplasmin deficiency. There is no copper overload. Transmission is autosomal recessive. DNA analysis showed genetic linkage between the deficiency and various polymorphic markers flanking the caeruloplasmin gene on chromosome 3q25. This is consistent with a mutation of the caeruloplasmin gene. Caeruloplasmin catalyses the oxidation of ferrous iron to ferric iron. Both brothers have low serum iron and increased liver iron. The index patient was given caeruloplasmin-containing, fresh-frozen plasma. A dose of 2.6 mg caeruloplasmin increased serum iron from 5 microM/l to 10 microM/l. A dose of approximately 72 mg increased serum iron from 5 microM/l to 19 microM/l. The abnormal serum and liver iron levels, and the caeruloplasmin-induced rise in serum iron, confirm a previous suggestion that caeruloplasmin maintains the normal rate of flow of iron from store to transferrin. Dementia and diabetes mellitus have been described in only one other homozygote. The absence of copper overload, and the linkage of the deficiency with chromosome 3q25, distinguish this condition from Wilson's disease.

CSIRO is undertaking several new initiatives in the Manufacturing sector including a Niche Manufacturing Flagship and a Theme based around nanoadditives for the fine chemical industry. These initiatives are designed to assist the Australian Manufacturing Sector to develop high value added niche products that can compete on local and international markets. The purpose of the "Nanoadditives for the Fine Chemical Industry" is to transform the Australian fine chemical industry by partnering with leading global and local companies, to identify, prioritise and provide new materials for niche markets for Australian fine chemical companies to manufacture value added additives.

The low temperature, reversibly adsorbed states (90–300 K) of water, n-alcohols, n-ethers, acetone, acetonitrile and n-alkanes have been studied with temperature programmed desorption (TPD) and spectroscopic methods (XPS, UPS) on clean Pt(111) and Cu(100) surfaces. Each molecule forms two distinct low temperature phases at 100 K; a multilayer or condensed phase and a weakly bound monolayer or precursor phase. The monolayer state usually desorbs at a higher temperature than the multilayer and can be isolated by selective desorption. We establish several general conclusions in relation to the weakly chemisorbed monolayers: (1) In the majority of cases, spectroscopic methods (EELS, XPS and UPS) show no significant chemical shifts in the monolayer relative to the condensed phase. Structural and orientational models are therefore proposed from an analysis of the thermal desorption data. (2) Monolayer heats of adsorption were found to be comparable ( ± 5 kJ/mol) to the heats of sublimation of the multilayers for most molecules. We demonstrate, however, that all of the molecules, with the exception of alkanes are chemisorbed in the monolayer. By analysing the heat of adsorption as a function of molecular size, the contributions from the oxygen lone pair bond in alcohols and ethers, and the Van der Waals attraction of the alkane chains to the surface can be separated. A CH2 group contributes 5–6.5kJmolto the heat on both metals, whereas the oxygen lone pair contributes 42 kJmol (Pt) and 35 kJmol (Cu), respectively. (3) Each of these weakly adsorbed monolayers may act as precursors to stronger, dissociative chemisorption as the temperature is raised. In most cases, however, the low temperature molecular phase is the only molecular state observed prior to desorption or subsequent dissociation. (4) Platinum binds weak electron donor molecules (alcohols, ethers, acetone, water) somewhat more strongly than copper. For acceptor molecules (e.g. acetonitrile), platinum back-donates electrons much more strongly than copper. These differences can be rationalized in terms of the orbital energy diagrams for the adsorbate and the band structure of the two metals, although a comprehensive bonding scheme has yet to be developed.

During the last few years a large body of research has developed around the use of positron techniques to study materials problems. The value of the positron as a probe into the structure of materials stems from the rather special characteristics of the gamma rays which result from the annihilation of the positron with its antiparticle, an electron. Positrons are positively charged particles and are attracted to regions of a solid with low nuclear density, such as defect sites. The annihilation gamma rays from positrons trapped at such sites have slightly different characteristics from those originating from annihilation events in the rest of the material, and this forms the basis of a truly non-destructive technique for detecting defects. This article describes some applications of positron annihilation to problems involving mechanical damage in alloys, with a special emphasis on the prospects for its practical use in non-destructive testing.

Platinum-tin catalysts prepared by different methods, and supported on γ-Al2O3 have been studied with X-ray Photoelectron Spectroscopy (XPS), temperature-programmed reduction, and reaction measurements. Two major conclusions are drawn from the results. First, tin is present primarily in the oxidized form (Sn(II)) after high-temperature reduction (500 °C) of Pt-Sn γ- Al 2 O 3 catalysts, whereas alloy formation can occur on silica under the same conditions. No evidence for substantial amounts of Sn(0) is found on reduced γ-Al2O3-based catalysts. The spectroscopic reduction results are in agreement with TPR measurements in the present (and previous) work which show an average Sn reduction of 50%. Even PtSn complexes, which are readily reducible to Sn(0), are not reduced below Sn(II) on γ-Al2O3. Second, quantitative XPS measurements of surface tin concentration versus bulk loading reveal an inhomogeneous distribution of tin in the impregnated γ-Al2O3 samples, with a large excess of tin on the external surface of Al2O3 at loadings below 1 wt% Sn. The results show that impregnation of tin followed by platinum can result in separation of the two components due to the strong adsorption of tin ions in the outer surface of the γ-Al2O3 particles. The best distribution of tin is found in the coprecipitated Sn-γ-Al2O3 (Patent) preparations where the tin is uniformly distributed throughout the matrix. The reaction measurements of catalysts prepared via the different methods are compared and it was concluded that the activities and selectivities in methylcyclopentane and cyclohexane conversion are sensitive to the method of tin introduction. A catalyst prepared via the coprecipitation of Sn with γ-Al2O3 followed by impregnation of platinum gave the highest sensitivities to activity and selectivity changes in the latter reactions. Whereas it is important to have platinum and Sn(II) in the vicinity of each other on the support, the mechanism of interaction is not well understood at this stage.

Small metallic particles with diameters in the range 1–100 nm have interesting properties which can sometimes be very different from those of bulk metals. Such colloidal particles play an important part in fields which range from catalysis to radiation damage in compound solids, and also have an intrinsic interest since in some respects they can be regarded as a state of matter intermediate between that of a molecule and a solid. In ionic crystals colloids can be produced either by irradiation or by the introduction of a stoichiometric excess of the metal constituent. In either case the colloids form as a result of the aggregation of fundamental point defects, but it is only fairly recently that a reasonably coherent picture of these processes has emerged and the properties of the colloids have been related to those of small metallic particles studied for other reasons. This review discusses the progress which has been made through the use of a large number of different techniques to study the pr...

In a recent paper, Kojima, Sugihara, Miyazaki and Yasumori concluded that methanol and formaldehyde adsorb molecularly (non-dissociatively) on polycrystalline copper at 300 K. Methanol and methyl formate were also found to produce adsorbed formaldehyde. We demonstrate that the “formaldehyde” UPS spectrum in their study was incorrectly assigned, and is identical to that of adsorbed formate generated during dissociative exposure of formaldehyde to a Cu(110) surface. We have measured the He II spectra of formaldehyde (120 K) and formate (300 K) on clean Cu(110) and show that they are distinctly different. No evidence is found in the present work for stabilization of molecular formaldehyde, methanol or methyl formate on the Cu(110) surface at 300 K.

This paper presents an algorithm for curve fitting XPS spectra by the damped non-linear least squares (DNLLS) technique. DNLLS is used extensively in optical design programs but has not previously been described in the XPS literature. Non-linear least squares (NLLS), which is a special case of DNLLS, has been described in the literature, but DNLLS is found in the present study to be a superior method of curve fitting XPS spectra, particularly when the fitted lineshape is complex.

The adsorption and reactions of methanol, methyl formate and formaldehyde on clean and oxygen-covered copper (110) surfaces has been studied with EELS, UPS and temperature programmed desorption (TPD). We report spectroscopic data for (a) the condensed multilayers at 90 K, (b) the surface monolayers and (c) the reaction intermediates formate (HCOO) and methoxy (CH 3 O) generated by reaction with surface atomic oxygen. On the clean surface methanol and methyl formate bond via the oxygen and carbonyl lone pair orbitals, whereas formaldehyde always polymerizes to surface paraformaldehyde above 120 K. Atomic oxygen generates methoxy by reaction with methanol and formate by reaction with formaldehyde as reported previously. Methyl formate undergoes nucleophilic attack to form both methoxy and formate in the presence of atomic oxygen, in a similar fashion to the reaction on Ag (110). Whereas the oxidation reactions of these molecules on copper catalysts can be explained with reference to the observed intermediates, no evidence is found for the dimerization of formaldehyde or the dehydrogenation of methanol to form methyl formate: reactions which are quite facile under higher pressure conditions.

The Lifshitz-Slezov-Wagner (LSW) theory of Ostwald ripening, limited by bulk diffusion or surface reaction rates, is extended to the case of dislocation or grain-boundary diffusion. The theory predicts a universal particle size distribution, F(R/Re), where RC is the critical radius i.e. the radius of a particle which is instantaneously in equilibrium with the solute concentration in the matrix. Some of the approximations used in the theory are critically examined. The approximation eulR 1 + m/R, used in applying Thomson's equation to the theory, is not always valid and can cause a significant error in the shape of the size distribution function for small values of R. Inhomogeneities in the distribution of interparticle separation can cause different groups of particles in the same solid to ripen independently, thus giving an observed size distribution which does not agree with the simple theory. A comparison of the theory with recent experiments on alkali halides and glass supports the above findings and explains a variety of observations satisfactorily. The observed size distribution of Ag particles in glass is described by two overlapping distributions for the bulk diffusion case. Ag particles in KC1 are described by the narrow distribution obtained for the dislocation diffusion case and the distribution of MnC12.6 NaCl (Suzuki phase) in NaCl by the surface reaction case when allowance is made for the errors due to the approximations discussed above. l. Introduction. The kinetics of precipitation from a supersaturation of solute atoms or defects in a crystal matrix have been extensively discussed by numerous authors e. g. [l-71, and recently applied to the aggregation of F centres into metallic colloids [g]. The precipitation process proceeds until the supersaturation of solute has become small, and most of the excess solute has been incorporated into precipitated particles. The particle size distribution during this process remains fairly narrow. However, this distribution does not persist, because the larger interfacial energy of a large number of small particles drives the system towards a situation where the mean particle size is increased. This process is known as Ostwald ripening, and in principle extends until the particles (*) Permanent address : Defence Research and Development Organization, South Block, New Delhi 11001 1, India. have grown into a single large precipitate or the solute has migrated to the surface of the crystal [9]. The mechanism of Ostwald ripening relies on the transport of solute from small precipitates to larger precipitates, so that the small ones shrink and the large ones grow. These solute currents arise because the solute concentration C, in equilibrium with a particle of radius R is given by Thomson's equation [9]. C , is the solute concentration in equilibrium with a plane surface and a = 2 SZalkT, where S2 is the atomic volume and a the interfacial energy of the particle in the matrix. Since CR is larger for small values of R a concentration gradient will exist so that solute flows from the region near a small particle towards a large particle. During Ostwald ripening a range of particle sizes will be present. Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19767103 C7-464 S. C. JAIN AND A. E. HUGHES The theory of Ostwald ripening was formulated by Greenwood [l01 and considerably extended by Lifshitz and Slezov [ll-121 and Wagner [13]. These theories predict that the ripening system evolves into a quasi steady state in which the size distribution F(u) expressed in terms of the reduced variable U = R!R does not change with time and in which the mean radius R grows as t"where n < 1. The exponent n is + when the ripening process is controlled by the rate at which solute evaporates and condenses at the particles (case l), and 4 when the rate-limiting process is bulk diffusion of solute atoms (case 2). Extensive experimental work has been done to test these theories in the case of metal alloys 191, with reasonable success. However, the observed size distributions are usually rather wider than predicted. Very little work has been done on ionic crystals and glasses, although size distributions of colloids and precipitates have been reported [14-181, and some attempt has been made to interpret the ripening results theoretically [19-211. In this paper we report a more extensive analysis of the experimental results, and extend the Lifshitz-SlezovWagner (LSW) theory in two important respects. The first of these is to cover the case where transport of solute between particles takes place by dislocation or grain boundary diffusion (case 3) rather than through the bulk crystal. We also show that it is possible under some conditions for different groups of precipitate particles to ripen almost independently in the same crystal. This leads to an interpretation of features of the observed size distributions which are not explained by the conventional LSW theory. Since the detailed arguments have been presented in another report [22] we shall concentrate only on the main results. 2. Ripening theory and its extension to dislocation and grain boundary diffusion. Suppose that the concentration of solute at a point distant from a precipitate particle is C,, i. e. C, represents the average value of the solute concentration in the bulk of the crystal. The rate of change of the radius of a particle is then given in the steady state approximation (see

Reduction of unpromoted Co- and promoted Co-ThO2-MgO-Kieselguhr catalysts has been studied with X-ray photoelectron spectroscopy and temperature-programmed reduction techniques. A mechanism of reduction is proposed based on spectroscopic measurements of the surface phases before and after H2 treatment at 400 °C. Cobalt oxide Co3O4 is present on all air-calcined catalysts, and is reduced rapidly to CoO at temperatures >300 °C in hydrogen. CoO is then more slowly reduced to Co metal on the unpromoted catalysts at 400 °C. If the promoters MgO and ThO2 are present, a reaction between CoO and promoter can occur resulting in new phases which are more resistant to reduction than CoO alone. XPS results suggest one phase as a CoO-MgO solid solution, but the CoO-ThO2 phase could not be identified. The cobalt in magnesia-promoted CoO phases is reduced completely to the metal at much higher temperatures (500–700°C) but at 400°C the surface reduction is limited to 55% ± 5 after 1 h. Variability in the degree of reduction of various promoted cobalt catalysts is therefore dependent on the nature and loading of the promoter and the reduction temperature. Promotion of a Co-Kieselguhr catalyst with ThO2 or MgO does allow a higher degree of control over the CoO reduction kinetics than is found with unpromoted catalysts.

The conditions for the initial formation and continued stable growth of a continuous film of oxide BOv on an alloy AB are derived, using simple arguments. The object is to expose the basic assumptions of the models used to describe the situations in which B is oxidized selectively, and to show in a simple way how the various limiting conditions relate to the diffusion processes in the alloy and its oxide.

Most tests of the dissolution behavior of glasses quote the leach rate, often measured in flowing solutions. In the past, it has been pointed out that this may not be the rate-determining factor for the dissolution of glass in a radioactive waste repository because of the very small flow rate of water past the glass surface. Under these conditions, the rate of removal of elements from the glass would be controlled by the flow rate and the effective saturation solubility of the glass in the water, or, in stagnant conditions, by the rate of diffusion of species dissolved in the water away from the glass surface. Simple quantitative models are developed to provide a framework for the discussion of these effects, and they indicate that in cases of practical importance it is indeed solubility and either water access or diffusion that together limit the rate of dissolution of the glass. It can be concluded that effective leach rates in a repository will be below 10/sup -7/ g X cm/sup -2/ X day/sup -1/, a figure that in other studies has given a clear margin of long-term safety for radiological purposes.

This report reviews the possible effects of both radiation damage to the glass and of radiolysis of the leachant on the leaching behaviour of vitrified radioactive waste. It has been stimulated particularly by recent papers, which have suggested that the leach rates of glasses will be enhanced by large factors after a ‘critical’ dose of radiation from alpha decays. These experiments have been conducted at highly accelerated rates using ion beams. The relationship between these experiments and the situation in vitrified waste has been assessed, taking into account the fact that experiments using alpha emitters incorporated in the glass have failed to find significantly enhanced leach rates after doses about five times larger than those equivalent to this ‘critical’ dose. It is concluded that these differences are observed partly because the ion beam experiments are carried out at such high dose rates that some recovery effects important at lower rates do not come into play. In the case of experiments with 2 keV argon ions, surface effects other than genuine radiation damage must be taken into account.In practice, if water has penetrated the canister, vitrified waste will be irradiated in the presence of the leaching solution. Enhancements of the leach rate due to the transient effects of radiation in the solid are shown to be completely negligible. The effects of radiolysis of the leaching solution and of any air in contact with the solution have also been considered in some detail and related to recent experiments by McVay and Pederson. It is shown that these radiolysis effects will not lead to any situations requiring special precautions in practice, although changes in surface leach rate by small factors can be expected under some circumstances.Any effect of irradiation on leach rates must be seen in the context of a waste repository. Along with other studies we hold the view that the rate of loss of material will be limited by the access of water to the repository, and will therefore depend on the effective saturation solubility of the glass in the leachant, not on the leach rate as usually determined in laboratory tests. Radiation damage is not expected to change the saturation solubility by more than a factor of two or three.

The optical absorption spectra of substitutional ${\mathrm{Cr}}^{2+}$ ($3{d}^{4}$) in single crystals of ZnS (cubic and mixed cubic-and-hexagonal), ZnSe, ZnTe, CdS, and CdTe have been measured for Cr concentrations of ${10}^{18}$-${10}^{20}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ and at 2, 15, and 300\ifmmode^\circ\else\textdegree\fi{}K in the wave-number range $5\ensuremath{\le}\overline{\ensuremath{\nu}}\ensuremath{\le}30000$ ${\mathrm{cm}}^{\ensuremath{-}1}$. The room-temperature spectrum in the range $500\ensuremath{\le}\overline{\ensuremath{\nu}}\ensuremath{\le}30000$ ${\mathrm{cm}}^{\ensuremath{-}1}$ is dominated by a broad absorption band at 5500 ${\mathrm{cm}}^{\ensuremath{-}1}$ arising from the $^{5}T_{2}\ensuremath{\rightarrow}^{5}E$ transition. These two levels originate from the crystal-field splitting of the $^{5}D$ free-ion ground state. At helium temperatures distinct lines appear on the low-energy side of the $^{5}T_{2}\ensuremath{\rightarrow}^{5}E_{2}$ absorption band in all samples except for CdTe. These lines are associated with zero-phonon transitions and phonon-assisted transitions. As the temperature is increased, the relative intensities of some of the lines change due to the thermal population of low-lying levels belonging to the orbital ${T}_{2}$ state. In the case of ZnSe these levels have been studied in the far infrared in the range $5\ensuremath{\le}\overline{\ensuremath{\nu}}\ensuremath{\le}200$ ${\mathrm{cm}}^{\ensuremath{-}1}$, both with and without a magnetic field. An interpretation of the results is made based on crystal-field theory with a strong, static, Jahn-Teller distortion of $E$ symmetry in the $^{5}T_{2}$ orbital ground state. There is little or no Jahn-Teller effect in the $^{5}E$ orbital excited state. The optical transitions exhibit a strong coupling to $E$-mode phonons of average energy \ensuremath{\sim}70 ${\mathrm{cm}}^{\ensuremath{-}1}$.

The optical absorption in Cr doped ZnSe has been measured for photon wavenumbes,, ν , from 2 cm−1 to the bandedge at about 20 000 cm−1 for temperatures from 1.2 to 300°K. The Cr produces an extremely sharp absorption line at ν = 7.43 cm −1 , additional broad absorption lines between 50 and 100 cm−1, a broad absorption band at 5500 cm−1, and some further structure at higher energies. As we will show, these results support the conclusion of earlier paramagnetic resonance studies that a static Jahn-Teller distortion of E symmetry is present in the ground state for Cr2+ ions in ZnSe.

The results of a series of experiments undertaken to examine the statistical theory of inhomogeneous strain broadening of optical lines in crystals are described. The system chosen for this investigation was the sharp N 1 colour centre absorption line in sodium chloride, the random strains being provided by doping the crystals with other alkali and halide ions. The general theory of strain broadening is summarized, and it is shown that in the isotropic continuum approximation the predictions of the theory regarding the shape, halfwidth and shift of the line as a function of impurity concentration involve no unknown parameters. The theory predicts a Lorentzian contribution to the lineshape from the impurity strain fields, and a shift and halfwidth proportional to the fractional change in lattice parameter and its modulus respectively. On the whole good agreement between theory and experiment is found. The experimentally measured lineshapes can be well fitted by a convolution of the Gaussian shape of the pure crystal and the Lorentzian contribution of the impurities, but the measured factors of proportionality linking the shift and halfwidth to the impurity concentration and lattice parameter change are 25 per cent larger than the theoretical predictions. Some possible reasons for this discrepancy are discussed in terms of the breakdown of the isotropic continuum approximation, the accuracy of the experimentally determined strain coupling parameters of the N 1 centre and the effects of defects ( F centres, interstitials, etc.) produced along with the N 1 centres. The origins of two groups of satellite lines observed in the doped crystals are discussed with reference to the structure of the N 1 centre, and interpreted as being due to N 1 centres having nearby impurity ions.

There is much concern that long-lived radioactive elements incorporated in glasses for the disposal of highly active nuclear waste might eventually return to the environment. The most important mechanism begins with leaching of the glass by groundwater and a leach rate, usually based on laboratory tests of simulated vitrified radioactive waste, has been used as the basis of analyses of the radiological safety of a waste repository1–3. The possibility that radiation damage to the glass from the products of nuclear decay could change the leach rate has been studied both by the incorporation of active elements in the glass and by irradiation from external sources. The most important contribution to radiation damage comes from the recoil nuclei during α decay4. Typically the recoil nucleus has a kinetic energy of ∼100 keV and displaces >1,000 atoms in the glass. Experiments which simulate this damage by incorporating short-lived α-emitting isotopes such as 238Pu into the glass have not shown significant increases in leach rate at doses equivalent to >1018 α decays g−1 (refs 5–9). Figure 1 shows that for wastes considered in the UK this corresponds to a time after vitrification of at least 103–104 yr. Recent work with ion beams inducing the radiation damage10–12 has suggested that large increases (up to a factor of just over 50) in leach rate will occur after a critical dose of radiation from the α-decay processes. In addition, experiments in which the leaching solution is irradiated with γ rays13–15 have shown that radiolysis effects in the water can increase the leach rates of glasses. We present here new data and calculations which relate these studies to the conditions expected in a real waste repository. Our analysis is described in more detail elsewhere16,17.

The shape and moments of the F+ absorption band in SrO have been measured between 4.2K and 300K. Analysis of the moments gives the effective frequency of the vibrational modes interacting with the centre as h ω = 236 ± 20 cm -1 , and the Huang-Rhys factors for cubic and non-cubic modes as SC = 3 ± 1 and SNC = 4 ± 1 respectively.

The strain broadening theory of Stoneham6 is applied to the results of Clayman et al .1 on the shift broadening of the KBr:Li+ resonance upon alloying with KCl and KI. Good agreement is found for the shift of the resonance frequency as a function of lattice parameter change, but the observed halfwidth suggests that the Li+ ions and impurity anions may be correlated in position.

The effect of magnesium impurities on the thermal stability of an irradiation-induced colour centre in LiF is described. Measurements of the splitting of a zero-phonon line at 8328 A under uniaxial stress show that the centre has trigonal symmetry. These results and evidence for the production of these defects by conversion from R centres support the identification as an R' centre.

Optical and infrared spectra of U centres formed by proton and deuteron irradiation of KCl are reported. The efficiency of formation of U centres is roughly one U centre per ten incident protons. U → F conversion by ultraviolet bleaching confirms that the implanted U centres behave in the same way as in chemically doped crystals.

ESR and ENDOR have been used to investigate the F+ centre in MgO crystals enriched in the isotope 17O. A study has been made of the hyperfine interactions between the trapped electron and 17O nuclei at the first four anion shells neighbouring the oxygen vacancy. The results are consistent with a wavefunction in which most of the unpaired spin is in 2p orbits on the twelve nearest O2- ions with smaller admixtures of 3s and 3p orbitals in the six nearest Mg2+ ions. There is also evidence for small 2p admixtures at further O2- sites.

The rate ofoxidation of metalsat high temperatures is usually controlled by the transport of metal ions or oxygen through the growing film of oxide on the surface. Since many technologically useful alloys (eg steels, nickelbased alloys) are based on the 3d transition metals, the transport properties of the oxides of these elements are of particular interest. In the temperature range 500–1000°C, where these alloys are used, the important transport paths in the oxide are not those that involve diffusion in the bulk crystal lattice, but other “short-circuit” paths. Basic experiments on the oxidation of nickel and direct tracer measurements of diffusion coefficients show that rain boundaries are the most important short-circuit paths under protective oxidation conditions. Similar conclusions can be drawn for other metals including chromium. The methods used in this work have been extended to study the way in which a surface treatment withCeO2reduces the oxidation rate of nickel, apparently by inhibiting the outward transport of metal ions along grain boundaries. Segregation of cerium ions to grain boundaries increases the diffusion coefficient of nickel; the inhibition is caused instead by particulates of CeO2in the middle region of the scale.

The interpretation placed by Murti and Sucheta [1] on their results of F ⇄ C conversion in irradiated NaCl is shown to be misleading. Their experiments are consistent with the accepted assignment of the C band to colloidal sodium centres.

The size distribution of silver colloids in additively coloured and annealed KCl is discussed. It is shown that the narrow distributions observed experimentally are best explained by particle growth taking place through diffusion of solute along dislocations.

The adsorption and reaction of methanoi (CH3OH), methyl formate (CH3OCHO) and formaldehyde (H2CO) on clean and oxygen-covered Cu(110) surfaces has been studied with EELS, UPS and thermal desorption spectroscopy (TDS). The clean surface is relatively unreactive but adsorbed oxygen readily attacks the hydroxyl proton and formyl carbon atoms to generate the intermediate methoxy (CH3O) and formate (HCOO). Methyl formate is split into two intermediates, methoxy and formate. By correlating the three techniques we analyse (a) the condensed multilayer at 90 K; (b) the weakly bound molecular monolayer states prior to dissociation or reaction and (c) the reactive intermediates at higher temperatures. Formaldehyde forms the surface polymer polyoxymethylene [(CH2O)n] in the monolayer on Cu(110) which subsequently reacts with oxygen to generate formate. No molecular formaldehyde was observed above 120 K. Correlation of the EELS and UPS results for polyoxymethylene shows that an earlier interpretation by Rubloff et al. [Phys. Rev. B14 (1976) 1450] of anomalous shifts in the formaldehyde UPS spectrum on surfaces is incorrect, and due simply to the new polymeric structure of surface formaldehyde. Methyl formate coordinates to copper via the carbonyl lone pair orbital and methanol via the oxygen lone pair orbital. No evidence was found for methyl formate synthesis by dimerization of formaldehyde (the Tischenko reaction) or dehydrogenation of methanol on the clean Cu(110) surface. These latter reactions are facile over copper catalysts at atmospheric pressure. The success of the oxidation experiments and the failure of the synthesis reactions in UHV is a consequence of the pressure dependence of the equilibrium constants for the different reactions. As found previously in Fischer-Tropsch studies, condensation reaction equilibria are pressure dependent and product formation is considerably suppressed at UHV pressures.