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In this work, a novel garnet-based Eu3+-doped Ca2GdHf2Al3O12 phosphor was synthesized through the traditional high temperature solid-state method. The phase purity, fundamental structure of the crystal, morphology, photoluminescence and cathodoluminescence properties have been investigated in detail. Along the temperature rises to 200 °C, the Ca2GdHf2Al3O12:0.08Eu3+ remains about 70.2% according to the initial emission intensity. Under the electron bombardment, the Ca2GdHf2Al3O12:0.08Eu3+ phosphor reveals a remarkably improved performance in the anti-degradation property. All results indicating that the Ca2GdHf2Al3O12:Eu3+ could be regarded as a valuable phosphor in the multiple industrial applications, such as WLEDs and FEDs.

A surface Ni-doped MgO-Au thin film was prepared by reactive magnetron sputtering and showed a superior secondary electron emission (SEE) performance under continuous electron bombardment in comparison with an undoped one. The experimental results show that the surface Ni-doping improves the electrical conductivity of MgO-Au film due to a size reduction of MgO particles and a bandgap narrowing of the surface MgO layer. Additionally, a 3.4 at% Ni-doped MgO-Au film exhibits an average SEE decay rate per hour as low as 2.6% with a reduction of 31.6% under continuous electron bombardment compared with the undoped one, and especially its SEE coefficient turns to be higher after 4-hour electron bombardment. Thus, the surface Ni-doping is an effective strategy to suppress the surface charging effect and subsequent SEE decay of MgO-Au film owing to the improvement of electrical conductivity.

We recorded the IR spectra of 2-C16H11 and 4-C16H11 trapped in solid para-hydrogen (p-H2). These species were produced on the electron bombardment of p-H2 containing pyrene (C16H10) in a small proportion during matrix deposition. IR absorption features of 1-C16H11+ and 1-C16H11 in solid p-H2 were previously identified [J. Phys. Chem. Lett. 4 (2013) 1989]. Here, the irradiation of a similar matrix sample at 365 nm depleted 1-C16H11+ and 2-C16H11 and produced 1-C16H11 and 4-C16H11. In contrast, irradiation at 405 nm decreased 1-C16H11+, 2-C16H11 and 4-C16H11. The identification of the observed lines of 2-C16H11, and 4-C16H11 was supported by predictions of the vibrational wavenumbers and relative IR intensities at the B3PW91/6–311++G(2d,2p) level of theory.

Oxidation of carbon monoxide on ultrasmall Au particles supported on LiF film has been studied by means of vibrational and thermal desorption spectroscopy. It is found that the efficiency of this process is dramatically enhanced when Au is deposited on defect LiF film obtained by electron bombardment to produce Fx−-centers. Local electronic charge of the Fx− center is a key point determining formation of an (C–O–O⁎) intermediate on (Au–Fx−) adsorption site as carbon dioxide precursor.

In order to investigate potential diffusive loss of He from apatites during SEM analysis, we performed (1) single-grain (U Th)/He dating for 47 Durango apatite fragments (from Th)/He ages are internally consistent within their errors, and indistinguishable from the reported 40Ar/39Ar ages of 31.44 ± 0.18 (2σ) Ma and the apatite (U Th)/He ages of 31.02 ± 1.01 Ma (Standard Deviation; McDowell et al., 2005 ). The results from the electron–matter interaction simulation suggest that “temperature rise” (ΔT = temperature increase during electron bombardment) peaks within a very thin layer at the outermost of the hypothetical apatite grain, and falls below ~ 50 K within a depth of 0.3 μm from the surface. Based on the simulated ΔT profile combined with available He diffusion parameters, the fractional loss of He (fHe) was calculated for different apatite grain dimensions. The numerical simulation supports that the He loss from apatite grains of typical physical dimensions is negligible ( Th)/He ages for SEM-treated apatites, as well as diffusion simulation using the electron–matter interaction model, indicate that SEM spot analysis or extensive chemical mapping prior to apatite (U Th)/He dating does not cause any meaningful diffusive He loss for most of the apatite samples.

We characterize the bombardment of energetic electrons onto Europa’s surface and discuss their influence on surface albedo, chemistry, and astrobiological potential, thereby isolating and quantifying a major contributor to exogenic processes affecting the satellite.

This paper presents the X-ray Photoelectron Spectroscopy (XPS) analysis for the undegraded and degraded Gd2O2S:Tb3+ thin film phosphor. The thin films were grown with the pulsed laser deposition (PLD) technique. XPS measurements were done on Gd2O2S:Tb3+ phosphor thin films before and after electron degradation. The XPS technique has proven the presence of Gd2O3 on the degraded and undegraded thin film spots. The presence of the SO2 bonding was also detected after degradation. This clearly indicates that surface reactions did occur during prolonged electron bombardment in an oxygen atmosphere.

Binary potassium silicate glass of composition 15 mol% K2O + 85 mol% SiO2 was irradiated with 50 keV electrons. Dependence of mechanical properties of the irradiated glass on electron doses were measured by means of nanoindentation. The reduced Young modulus and hardness decrease for higher doses. The changes in mechanical properties are dominantly determined by the density variation and silica network depolymerisation during the electron bombardment.

Nano-Fe powders could be prepared only after 10 hours of ball milling assisted by dielectric barrier discharge (DBD), whose particle mean size was about 100 nm. The synergetic refinement mechanism of DBD on ball milling had been investigated by examining the morphology of Fe powder using scanning electron microscopy and transmission electron microscope. It was shown through SEM that Fe particles displayed an extraordinary plasticity in the early assisted milling stages under the action of DBD, and the plastic deformation of Fe particles was more severe than that in normal milling. Large quantity of Fe particles about 50 nm were observed by TEM which were generated during ball milling owing to the hot explosion effect caused by DBD electron bombardment. It was indicated that the refinement of Fe powder in DBD assisted ball milling could be promoted by the synergy effect of superplasticity, hot explosion and huge pulsating stress which were caused by the high-energy electron bombardment.

We analyze the quantum properties of the light generated by a two-level laser in which the two-level atoms available in a closed cavity are pumped to the upper level by means of electron bombardment. We carry out our analysis by putting the noise operators associated with a vacuum reservoir in normal order. The normal ordering of the noise operators leads to normally-ordered quadrature and photon-number variance. It so turns out that the light generated by the two-level laser operating well above threshold is coherent and the light generated by the same laser operating at threshold is chaotic.

In recent years e-cloud related processes have been understood to play a major role in limiting the expected performances of some present and planned accelerators. Big efforts have been then devoted to the detailed comprehension of the process and more and more refined simulation codes have been produced in order to be able to predict and control such effects. Essential input parameters to such calculations are a number of surface related properties whose detailed study has attracted growing attention. In this context, surface science studies can address a number of important issues like photo and electron reflectivity, photo- and electron-induced electron emitted energy spectrum, surface changes as induced by photon or electron bombardment, etc. Here, I present some experimental results of interest to e-cloud studies performed by means of state-of-the-art surface science techniques.

In the time-of-flight spectrum of positive ions produced by electron bombardment of NaCl surface a delayed signal of Na + is detected. This observation is attributed to production of core-excited autoionizing metastable Na ** atoms which have their characteristic lifetimes in the 100 ns range. Moreover, it is noticed that the populations of the various metastable Na ** states depend on the NaCl layer thickness. The lifetimes of some quartet metastable Na ** states have been determined as well.

A UHV system equipped with a standard LEED/Auger diagnostic has been modified to permit the measurement of the coefficient of secondary electron emission, δ, under electron bombardment. In order to measure the coefficient on insulators, the beam is pulsed. Problems due to charging are alleviated by alternating between pulses in which the target charges negatively (δ 1). The measuring technique is demonstrated by means of results obtained on mica and alumina. Residual and intrinsic charging effects are discussed.

Temperature-programmed desorption studies of submonolayer coverages of nitric oxide (NO) on a Ge(1 0 0) (2×1) surface have previously determined the non-dissociative nature of the adsorption of NO on Ge(1 0 0) at 110 K. Subsequent electron bombardment results in electron-stimulated desorption of N 2 O and N 2 at that temperature, without heating, which is attributed to the formation of NO dimers on the cold surface. This conclusion is supported by studies of adsorbed layers of N 2 O, which is adsorbed at least partly non-dissociatively, and which yields little desorption of the parent N 2 O molecule when bombarded with electrons.

Electron beam irradiation of polycrystalline boron doped Ni3Al (at 300 K and under ultrahigh vacuum conditions) induces fast oxidation. The rate and depth of oxidation initially increase with increasing electron flux as indicated by results from Auger electron spectroscopy. Curves of oxygen development were fitted using a kinetic model that assumes the creation of oxide nucleation centers by the electron beam. The corresponding cross-sections were extracted. For fluxes exceeding 1 mA/cm(2), the oxidation rate is limited by the amount of oxygen present in the vacuum environment. For lower e-beam fluxes the oxidation process is slower with significant O chemisorption, resulting in shallower oxidation. These findings point out a way to control the thickness of nickel oxide in the nanometer range. (C) 2002 Elsevier Science B.V. All rights reserved.

We report measurements of electron-stimulated desorption of core-excited autoionizing states of lithium from an LiF surface. In the time-of-flight spectrum a delayed signal of Li+ is observed. Its analysis indicates that at least three autoionizing transitions are active in the Li+ desorption process. They are as follows: Li**(1s 2p2)4P5/2→Li+(1s2)1S with a lifetime of (379±9) ns, Li**(1s 2p2)4P5/2→Li**(1s 2s 2p)4P5/2,3/2 with a lifetime of (8.3±0.8) ns, Li**(1s 2s 2p)4P5/2→Li+(1s2)1S with a lifetime of (5.2±0.3) μs, and Li**(1s 2s 2p)4P3/2→Li+(1s2)1S with a lifetime of (301±2) ns. The relative contributions of Li**(1s 2s 2p)4P5/2 and Li**(1s2s2p)4P3/2 components are equal to 0.33±0.02 and 0.67±0.02, respectively. Our lifetime values are consistent with those obtained by other experimental methods. Possible processes leading to the desorption of core-excited Li atoms are discussed.

A series of three sodium–potassium-silicate glasses with different alkali contents were prepared. The glasses were exposed to a 50 keV electron bombardment of defocused beams of various current densities. Decay curves (alkali X-ray intensity versus time) have been measured and analysed to obtain incubation periods and maximum transport rates. Obtained data have been compared with those known for binary alkali-silicate glass. The results confirm the influence of the mixed alkali effect on the transport behaviour of alkali ions under the electron bombardment.

Turbomolecular pumping groups are widely used in accelerators for the pre-evacuation and during the bake-out of the vacuum system. A major requirement for these groups, apart from pumping speed considerations, is the cleanliness of the vacuum produced. In an attempt to clarify this question, a bakeable low-pressure vacuum system has been constructed to allow the direct comparison of the contamination introduced by a turbomolecular pump and by an ideally clean cryopump. This contamination has been checked by the quantitative analysis of the residual gas as well as of the gases desorbed from surfaces under electron bombardment. Contamination by the rotary pump oil is only apparent below 40% of the turbomolecular pump nominal rotation speed. When the pump is stopped, the system is contaminated by heavy hydrocarbons which can be eliminated by a 300°C vacuum bake out.

Auger electron spectroscopy (AES) and cathodoluminescence (CL) measurements showed that surface reactions with the consequent loss of CL intensity occur for both the ZnS:Cu,Al,Au and ZnS:Ag,Cl phosphor powders during prolonged electron bombardment. Although ZnO layers formed on both the ZnS phosphor surfaces there is a difference between the degradation behaviour of these two phosphors. Surface charging occurs during electron bombardment of the aged ZnS:Ag,Cl phosphor due to the formation of a non-conductive ZnO surface layer. Charging of the ZnS:Ag,Cl phosphor resulted in a delay in the surface reactions and to an increase in the CL degradation rate due to band-bending. A much slower degradation in CL intensity was measured for ZnS:Cu,Al,Au, where no charging occurred.

We describe a UHV sample holder that allows fast heating and cooling cycles between 77 K and 1300 K. The system allows us to perform thermal treatment of a sample. The samples are heated by electron bombardment and the cooldown is achieved by liquid nitrogen (LN 2 ). The sample holder is designed to be assembled in a multitechnique surface analysis apparatus that performs AES, SIMS, TDS and XPS analysis.

Low index surfaces are in most cases stable even after adsorption, whereas vicinal surfaces may be only stable without or even with adsorbates. Since these phenomena are rather frequently reported, some carefully studied examples are discussed here, to show the importance of the effect and possible reasons for the sometimes dramatic morphology changes. Metals on semiconductors and metals are well studied and therefore the best examples for the present purpose. Since vacancies at the surface may act as point defects in a similar way, f-centers on NaCl are included into the discussion.

The first stages (exposures 4 L) of thermally stimulated oxidation of GaAs(100) have been studied using Auger electron spectroscopy and principal component analysis. We compare the GaAs oxidation processes taking place at high (700 K) and room temperatures, and during simultaneous electron bombardment and oxygen exposure. We found that while at room temperature, GaAs oxidizes via a one-phase process involving the simultaneous oxidation of Ga and As, the high temperature process is characterized by the presence of two different GaAs oxide phases. The first phase involves the simultaneous oxidation of Ga and As while in the second, only Ga oxides are formed. On the other hand, under simultaneous oxygen exposure and electron irradiation, two different oxide phases appear, both of them exhibiting the same features of the room temperature process, i.e., the simultaneous oxidation of Ga and As.

Measurements have been made of the total cross sections for ionization of the K-shell by bombarding thin foil targets with 50 keV electrons from a gun in the case of the elements Ti, Cr, Ni and Cu. The corrections for electrons reflected by the substrate were performed using a bipartition model of electron transport. The results are compared with the theoretical calculations and the earlier experimental results.

New experimental results on in-situ observations of radiation damage and time-compressed aging studies of organic scintillating fibres generated by 16 MeV electron bombardment are reported. The observed in-situ degradation has for low fluences a nearly linear and for high fluences a logarithmical decay. Typical selfannealing effects can also be characterized by logarithmical behaviours. A total recovery of optical properties for energy doses above 20 Mrad is absent.

The neutral species desorbed from the surface in the etching reaction of silicon have been identified from the measurements of their velocity distributions using a time-of-flight (TOF) technique combined with an electron bombardment ionization mass spectrometry. The preliminary measurements of the velocity distributions indicate that the desorbed species formed in the etching reactions of Si with XeF2 are essentially identical for the undulator light (h ν=35.8eV) on and off although irradiation of synchrotron radiation (SR) promotes the etching reaction.

L shell X-ray emission rates usually used as a part of a data base for analysis of PIXE spectra are theoretical values based on Dirac-Hartree-Slater (DHS) [J.H. Scofield, At. Data Nucl. Data Tables 14 (1974) 121] or Dirac-Hartree-Fock (DHF) [J.H. Scofield, Phys. Rev. A 10 (1974) 1507] calculations, or semiempirical data of Salem et al. [At. Data Nucl. Data Tables 14 (1974) 91], obtained from pre-1974 experiments with radioactive sources or sources ionized by photon or electron bombardment. Recently published L-subshell X-ray production cross sections by proton impact have been used to extract relative L-shell X-ray emission rates for some groups of L-shell X-ray lines, in order to compare them with the values from the three data bases mentioned before.

A preparation procedure for making thin self-supporting boron targets is described. The method is based on the preparation of a pre-fused lump and subsequent evaporation by electron bombardment. Using isotopically enriched material, uniform films of 30–60 μg/cm2 with low carbon and oxygen contamination were obtained.

First measurements of the energy-dependent desorption cross sections near threshold energy for electron-stimulated desorption of excited CN molecules from potassium-metal surfaces are presented. Threshold energies were observed to be different when the alkali metal surface was exposed to a CO 2 + N 2 mixture from that when exposed to H 2 gas, leading to the conclusion that two different chemical processes are involved. The rotational energy distribution was observed to be independent of incident electron energy. We postulate a desorption model similar to the Antoniewicz model.

Sputtering of films of solid deuterium by keV electrons was studied in a cryogenic set-up. The sputtering yield shows a minimum yield of about 4 D 2 /electron for 1.5 and 2 keV electrons at a thickness slightly larger than the average projected range of the electrons. We suggest that the yield around the minimum represents the value closest to a bulk-yield induced by electron bombardment. It may also include contributions from the mechanisms that enhance the yield for thin and very thick films.

Measurements are reported of the electron excited luminescence of several alkali halides at temperatures down to 110 K. Specimens were mainly in the form of evaporated films and the luminescence was excited by electron beams with energies between 50 and 200 eV. In several cases the low temperature luminescence contained contributions from the de-excitation of the self trapped exciton and good agreement with previously reported bulk measurements was obtained except in the case of CsF. Evidence of the de-excitation of the free exciton at the band edge was obtained in the luminescence spectrum of KI.

Heating of synthetic Mn-bearing and rare-earth element (REE) -bearing calcite in the temperature range 200–490°C causes changes in the intensity of cathodoluminescence (CL) emission. Both calcite: Mn and calcite: REE are affected quantitatively to a similar extent by heating which, in the majority of experiments, causes an intensity increase by a factor of up to 2.9. Within this 200–490°C range, the temperature at which heating is carried out has no significant influence on the magnitude of the effect. Below 250°C the effect of heating is duration-dependent but data at higher temperatures are ambiguous. Heating at 100°C for 2376 hr failed to produce a change in CL intensity. The magnitude of the heating effect depends on the starting material, but it is independent of dopant and impurity concentrations. Centroids and half-widths of the emission maxima are unaffected by heating. Neither the composition nor the intra-crystalline distribution of the activator(s) change during heating. Prolonged electron bombardment causes a systematic reduction in CL intensity. The initial rate of change of intensity reduction is least for synthetic calcite, intermediate for natural calcite and greatest for heated synthetic calcite. The effect of heating is attributed to the destruction of growth defects which reduce the CL intensity. The effect of prolonged electron irradiation is attributed to the creation of defects. Further work is required to characterize the controls on the magnitude of the heating effect; nevertheless the results suggest that, in principle, it may be possible to use CL as a geothermometer.

Low-energy (3–100 eV) electrons are shown to be efficient promoters of the superficial nitridation of thin SiO2 films grown on boron-doped Si(100) using low pure NH3 pressures (⩽2 × 10−4 mbar) at ambient temperature. The initial concentration (≈1015 at. cm−3) of ionized acceptors in silicon near the SiO2/Si interface is first lowered by the nitridation process and then restored by hydrogen annealing at 450°C. The ultrahigh vacuum experimental set-up permits us to uncouple two important effects from a thermally-assisted (700–950°C) r.f. NH3 plasma nitridation process: the role played by low-energy (3–5 eV) electrons and the temperature. It is found that the existence of charge particles near the sample surface must be taken into account in the plasma reaction process and that the main effect of thermal activation is to enhance the reaction and the diffusion of nitrogen species through the SiO2 layer up to the SiO2/Si interface.

The investigation and development of methods of preparation of nuclear targets which have been used for nuclear physics experiments at IMP since 1975 is described. Targets of more than 40 elements, including natural elements, enriched isotopes, lanthanides and actinides, have been produced. Equipment and procedures have been developed for many preparation methods such as electroplating, focused heavy-ion beam sputtering, centrifugal precipitation, rolling, electron bombardment, and resistance heating. The analysis of target films contaminated by oil vapor and the equipment for preparing thin, metallic self-supporting target foils without oil vapor contamination are also described.

Low energy (3–100 eV) electrons are shown to be efficient promoters of the superficial nitridation of thin SiO 2 films grown on boron-doped Si(100) using low pure NH 3 pressures ( -1 mbar) at ambient temperature. The initial active boron concentration in silicon (≌10 15 cm -3 ) is first lowered near the SiO 2 /Si interface by the nitridation process and then restored by a hydrogen annealing at 450°C. The ultra-high vacuum experimental set-up permits us to uncouple two important effects from a thermally-assisted RF NH 3 plasma nitridation process : the role played by low energy (3–5 eV) electrons and the temperature. It is found that the presence of electrons near the sample surface must be taken into account in the plasma reaction process and that the main effect of thermal activation is to enhance the reaction and the diffusion of nitrogen species through the SiO 2 /Si interface.

A computer simulation study, using Finnis-Sinclair-type N -body potentials, of the amorphization of crystalline CuTi 2 by electron bombardment was carried out. It was shown that the thermodynamic properties of volume and total energy cannot be generally used as criteria for amorphization. Instead it was found that, at the completion of amorphization, the magnitude and distribution of the atomic level shear stress was identical to that of the glassy state formed by a quench from the liquid. It is suggested that the atomic level shear stress provides a universal criterion for the attainment of the amorphous state, through glass transition, alloying, and solid state amorphization.

A detailed study of the transformation of graphitic structures into spherical onion-like particles under electron bombardment is presented. This evolution has been monitored up to the atomic details in a high-resolution electron microscope. The transformation from a tubular or polyhedral graphitic particle into a quasi-spherical onion is made in several steps, firstly the innermost shell collapses, then the regraphitization begins in the surface and follows towards the center by a sort of internal epitaxy.

The reaction of oxygen on the Nb (110) surface at 240 K after exposure to H2O and O2 under e-bombardment has been investigated by using AES and EELS techniques- The uptake of oxygen atoms is much more efficient when the surface is exposed to H2O than to O2. The chemistry of the oxygen adatoms is analysed on the basis of the AES Nb(M45N23V) and EELS structures. At the highest H2O exposure the oxygen atoms are in the form of Nb2O5 oxide, while for O2 the final state is an oxide of less valence. Initial sticking coefficients of ~ 1 and 0.41 for oxygen and water respectively, at 240 K adsorption temperature, have been determined. A model based on dissociative adsorption and electron stimulated desorption processes is presented to explain the differences between both molecules.

Measurements on electron stimulated desorption (ESD) of Li atoms in the electronical ground state (Li 0 ) from air-cleaved LiF(100) surfaces have been performed. The electron energy was varied between 50 and 450 eV. After electron bombardment was stopped, a prompt decrease of the Li 0 signal followed by a delayed emission of Li 0 was observed. In the temperature range from 620 to 720 K the delayed emission of Li 0 shows a behavior, which could not be explained by diffusion of F centers to the surface only. Delayed emission of Li 0 up to minutes was observed and we therefore suggest, that energy must be stored in the bulk through the formation of F center aggregates in order to explain the experimentally observed behavior of the delayed emission. A system of rate equations has been developed, which describes the kinetics of formation and decay of F center aggregates.

L-shell X-ray production cross sections are presented for selected elements with X-ray energies between 341 and 1188 eV. X-ray measurements were made using both a windowless Si(Li) and a windowless high purity Ge detector. The efficiency of the Si(Li) detector was determined by comparing bremsstrahlung spectra from electron bombardment of thin foils of aluminum, silver, and gold with theoretically determined bremsstrahlung spectral distributions. The efficiency of the Ge detector was determined by normalizing K-shell X-ray measurements to the Si(Li) detector. The measurements are compared to the first Born and the ECPSSR theories. The ECPSSR theory is shown to be in much closer agreement with the data.

Interest in the activity of electron beams at surfaces stems from both their deleterious effects in analysis, and the possibility of achieving highly localised control of surface chemistry. In this study, the interfaces formed with water at the (100) and (111) surfaces of silicon are seen to be critically controlled by electron bombardment. An initial stage of surface oxygen production is observed within the irradiated area, which is attributed largely to beam-induced H + desorption. A second, faster, stage follows, linked to a quasi-catalytic role played by the oxygen layer.

Lithium fluoride films, about 1.5 μm thick, thermally evaporated onto silicon substrates were subjected to low energy electron bombardment. Intense photoluminescence, extending from green to red in the visible spectral range was measured at room temperature in the irradiated areas, due to the presence of the laser active F2 and F3+ colour centres.

Arrangements have been made to make carbon stripper foils by electron bombardment, ethylene cracking and resistive heating. The deposition rate was found to be 0.35 μgcm −2 s −1 during the glow discharge and 0.02 μgcm −2 s −1 in the other two processes. An optical gauge was assembled to measure the thickness of stripper foils. An alpha thickness gauge setup was made to measure the thickness of four foils at a time without breaking the vacuum in the chamber. The thickness uniformity of 22 foils of a glow discharge batch was found to be 4%. An attempt is made to make the devices to test the strength of the foils made by these different techniques.

Techniques for preparing self-supporting targets between 45 and 450 μg/cm2 from separated isotopic boron by electron bombardment or focused ion beam sputtering are discussed. Microscope slides coated with betaine or nickel plates are used as substrates from which strong self-supporting foils with little residual stress were floated. A spectrophotometer has been used to measure the thickness of boron targets prepared by electron bombardment.

Copyright (c) 1997 Elsevier Science B.V. All rights reserved.It was found that introduction of Sc into Y 3 (Al,Ga) 5 O 12 :Tb is effective for reducing the phosphor degradation by electron bombardment. Thermoluminescence (TL) measurements show that no new TL active traps related to Sc are formed in the phosphor lattice. It was also observed that the TL intensity decreases with an increase in Sc concentration. It is proposed that this effect of the Sc doping is related to the more closed packing of the lattice.

A method for minimizing the distortion of the isodose contours created by tissue surface irregularities and for targeting the depth of maximum dose at an effective tissue depth during radiation therapy to a treatment field from a source is described. The method comprises the steps of: (i) placing an effective thickness of an anionic polymeric hydrogel into operational contact with the treatment field prior to the therapy; and (ii) administering the therapy in a manner such that the effective thickness of the anionic polymeric hydrogel is between the source and the treatment field, and the anionic polymeric hydrogel is in operational contact with the treatment field while the therapy is being administered. A preferred method is also described for marking the surface area of electron bombardment and radiation treatment portals on individuals prior to diagnostic magnetic resonance imaging. The method comprises the steps of: locating the area on the individual desired to be marked; selecting an appropriate marking device comprising an anionic polymeric hydrogel formed into a shape having at least one dimension of sufficient thickness to be discernable in a magnetic resonance image; placing the marking device at a location sufficiently near the located areas to appear in the magnetic resonance image and to indicate the location of the located area; and performing the magnetic resonance imaging while the marking device remains in place.

This source is based on the production of a beam of metastable atoms of 3He∗ in the 23S1 state, magnetic multipole selection of hyperfine components (Stern-Gerlach method), enhancement of nuclear polarization via an rf transition and ionization in an electron bombardment ionizer at 0.2 T. It is now installed inside the terminal of a CN 7.5 MV machine and is operational at a pressure of 7 atm.

Bulk AgSbSe 2 was prepared by melting the constituents in stoichiometric proportions in a sealed quartz ampoule. Films were prepared by single-source thermal evaporation in vacuum. The bulk material and the films were characterized by X-ray and electron diffraction studies and the results are reported. The crystallization of amorphous thin films by electron bombardment inside the electron microscope and also by external thermal annealing was observed.

The electron bombardment of molecules generally gives rise to ions in more than one electronic state. The ion beam composition with respect to the electronic states can be determined by studying the attenuation of the beam as a function of the pressure of a suitable gas. In this way, the composition of B + , F + , C + , H 2 O + and H 3 O + ion beams was determined. The difference between the reactive behavior of the ion beam in the ground and the first excited state with simple targets such as molecular hydrogen and its stable isotopic variants and some of the factors which determine the amount of excited state produced were examined.