Search

Background Recently, a new family of 99mTc(I)-tricarbonyl complexes bearing an acridine orange (AO) DNA targeting unit and different linkers between the Auger emitter (99mTc) and the AO moiety was evaluated for Auger therapy. Among them, 99mTc-C3 places the corresponding radionuclide at a shortest distance to DNA and produces important double strand breaks (DSB) yields in plasmid DNA providing the first evidence that 99mTc can efficiently induce DNA damage when well positioned to the double helix. Here in, we have extended the studies to human prostate cancer PC3 cells using the 99mTc-C3 and 99mTc-C5 complexes, aiming to assess how the distance to DNA influences the radiation-induced biological effects in this tumoral cell line, namely, in which concerns early and late damage effects. Results Our results highlight the limited biological effectiveness of Auger electrons, as short path length radiation, with increasing distances to DNA. The evaluation of the radiation-induced biological effects was complemented with a comparative microdosimetric study based on intracellular dose values. The comparative study, between MIRD and Monte Carlo (MC) methods used to assess the cellular doses, revealed that efforts should be made in order to standardize the bioeffects modeling for DNA-incorporated Auger electron emitters. Conclusions 99mTc might not be the ideal radionuclide for Auger therapy but can be useful to validate the design of new classes of Auger-electron emitting radioconjugates. In this context, our results highlight the crucial importance of the distance of Auger electron emitters to the target DNA and encourage the development of strategies for the fine tuning of the distance to DNA for other medical radionuclides (e.g., 111In or 161Tb) in order to enhance their radiotherapeutic effects within the Auger therapy of cancer.

P. AUGER entdeckte 1926 den nach ihm benannten Auger-Effekt. Dabei handelt es sich um einen strahlungslosen Ubergang in der Elektronenhulle eines Atoms. Infolge eines Primarelektronenbeschusses werden sogenannte Augerelektronen emittiert, deren Energie fur jedes Element charakteristisch ist. Damit lassen sich qualitative und quantitative Elementanalysen durchfuhren.

To anyone who is interested in surface chemical analysis of materials on the nanometer scale, this book is prepared to give appropriate information. Based on typical application examples in materials science, a concise approach to all aspects of quantitative analysis of surfaces and thin films with AES and XPS is provided. Starting from basic principles which are step by step developed into practically useful equations, extensive guidance is given to graduate students as well as to experienced researchers. Key chapters are those on quantitative surface analysis and on quantitative depth profiling, including recent developments in topics such as surface excitation parameter and backscattering correction factor. Basic relations are derived for emission and excitation angle dependencies in the analysis of bulk material and of fractional nano-layer structures, and for both smooth and rough surfaces. It is shown how to optimize the analytical strategy, signal-to-noise ratio, certainty and detection limit. Worked examples for quantification of alloys and of layer structures in practical cases (e.g. contamination, evaporation, segregation and oxidation) are used to critically review different approaches to quantification with respect to average matrix correction factors and matrix relative sensitivity factors. State-of-the-art issues in quantitative, destructive and non-destructive depth profiling are discussed with emphasis on sputter depth profiling and on angle resolved XPS and AES. Taking into account preferential sputtering and electron backscattering corrections, an introduction to the mixing-roughness-information depth (MRI) model and its extensions is presented. This book presents the basics of Auger- and X-Ray Photoelectron Spectroscopy in Materials Science in logical order from sample preparation and instrument setup through data acquisition to data evaluation. Offers guidance on problem-solving and worked examples.

Unlike in the previous Chap. 5, an atom or a molecule may lose two of its electrons in two consecutive steps as well (e.g., Fig. 3.1). While its primary ionization (i.e., loss of first electron) is caused from the energy supplied by some external source, the secondary ionization (i.e., emission of second electron) takes place in the rearrangement of electrons resulting from the primary ionization. Such a rearrangement of electrons becomes necessary whenever an inner-shell electron leaves the target in latter’s primary ionization. However, it is equally possible that such a rearrangement may lead to the emission of a photon in place of an electron (e.g., Fig. 3.2). This loss of energy in the form of a photon by, or departure of an electron from, an atom or a molecule due to rearrangement of its constituents is known as spontaneous radiative or non-radiative decay, respectively. The non-radiative decay was first observed by Auger [73, 74, 175, 176, 261]. The secondary ionization is, therefore, also known as Auger decay and the emitted particle called an Auger electron, say, ea. In this monograph, we will consider the primary ionization due only to the absorption of a single photon and, hence, the emitted particle will be known as a photoelectron e​p (say).

Using the Auger Engineering Radio Array (AERA) as a digital radio interferometer requires about the same relative timing precision and accuracy of contrast to LOPES which is externally triggered, AERA is planned to record self-triggered events with a high signal-to-noise ratio sufficient to detect the radio pulse already in individual antennas. An event whose signal-to-noise ratio is so low that it could only be detected with interferometry will not be triggered. Thus, interferometry will not lower the detection threshold of AERA.

In this chapter, we collect and comment figures and tables, which present data, obtained in calculations of photoelectron satellite intensities and line shapes, intensities of Auger spectra, some line shapes of low-energy Auger lines, and radiation widths.

Thin-film solar cells with Cu(In,Ga)Se2 absorbers offer a low-cost perspective at high photovoltaic performance. These solar cells generally consist of a ZnO/CdS/Cu(In,Ga)Se2/Mo thin-film stack on a glass substrate. The Cu(In,Ga)Se2 absorber layers do not exhibit homogeneous compositions but gradients of the Ga and the In concentrations across the layer thickness. The analysis of these gradients is important in order to gain information on the optoelectronic properties of the Cu(In,Ga)Se2 thin films, since CuInSe2 has a different band-gap energy (1.0 eV) to CuGaSe2 (1.7 eV).

Why is the extrusion of ceramics using an auger such a widespread and successful technology? Why is it that the auger extruder is of such interest to industry? What do we know about it? When will it work? How does it happen that the auger, a type of well-established equipment that certainly still lacks a complete scientific basis for its design, finds itself as the technology of choice in business for so many established and new products? Questions such as these underlie the discussion here.

Two types of RF picosecond timing technique: Cherenkov detector based on the radio frequency picosecond phototube and time-zero fission fragment detector are proposed. Study of hypernuclei by pionic decay and Auger neutron spectroscopy of hypernuclei at CW RF driven electron beams by using new RF picosecond timing technique are discussed.

Using a series of spectra excited by different heavy ion projectiles in different charge states the identification and the angular distribution of several Auger fines have been determined. For some transitions the presence of the A4 term in the angular distribution has been demonstrated. The alignment parameter calculated for states of type 1P,3P does not depend on the number of electrons in the target, while a rather strong dependence on the projectile Z number has been found.

Electron rearrangement of fast heavy ions passing through solid targets has been studied by the Monte Carlo simulation. Starting from the electron configuration of ions in solids, the change in electronic states due to successive radiative and Auger transitions was traced from the time when the ion emerges from the solid surface to the time when it is detected. The calculations were made for 63-MeV Cu ions emerging from carbon target. It is found that the charge increase due to vacancy cascade plays a minor role for the mean charge difference between gases and solids. The origin of the shell effect in the equilibrium charge distribution of ions is discussed.

The lifetime, TAl due to the,two-band, Auger 1 recombination mechanism is calculated for degenerate n-type (Hg,Cd)Te as a function of equilibrium carrier concentration, no under low modulation. For no sufficiently large so that the Fermi energy, EF is at least a kBT above the conduction band minimum, τAl ∝ 1/no/γ where γ < 1. For x = 0.2 and 50K ≤ T ≤ 200K, 0.7 ≤ γ ≤ 0.8. For EF(no) at least 3 kBT below the conduction band minimum, τAl ∝ 1/no/2.It is also found that in the degenerate region, τAl decreases with T for fixed no.

Luminescence measurements on Si and Ge at temperatures of about 1.5 K are presented, which indicate that Auger recombination is the main recombination process inside the electron-hole drops (EHD) in both materials. In silicon a broad spectrum near 2 Eg due to Auger- excited hot electrons could be detected. From its intensity, an Auger lifetime can be derived which corresponds to the total EHD lifetime. In germanium, the evaluation of magnetooscillation in the luminescence intensity yields a quantum efficiency of only 25% and leads to the conclusion that 75% of the carriers inside the EHD recombine in Auger processes.

Time-resolved pump-probe experiment was applied to porphyrin J aggregates. New relaxation model with two kinds of Auger processes is proposed and investigated to explain the spectral and decay features of our experimental results.

A new low energy scanning analytical microscope (LeSAM), combining scanning electron microscopy (SEM), scanning low energy electron microscopy (SLEEM), Auger electron spectroscopy (AES) and scanning Auger mapping (SAM), was realized using a new mini-electron column in conjunction with a cylindrical mirror analyser (CMA). The SLEEM mode of operation uses a cathode lens in which the specimen is negatively biased. In this arrangement, electrons pass through the microscope at high energy and are decelerated to a low incidental energy at the specimen. A novel 6 segment angular resolved in-lens detector is employed for signal detection. The new mini-electron column in SLEEM mode gives high resolution for primary incident beam energies of a few eV. For AES and SAM modes of operation a 6 segment angular resolved detector is also employed for signal detection.

This chapter deals with the importance of non-radiative processes which can severely limit the luminescence properties of nanocrystals. We give two detailed examples of such processes: multi-phonon capture at surface point defects and Auger recombination of electron—hole pairs. Both are known to play a central role not only for silicon but also III–V and II–VI semiconductor nanocrystals embedded in different types of matrices. As a typical example of surface point defect, we choose the dangling bond for silicon crystallites in a SiO2 matrix. The reason is that the properties of such defects at the planar Si—SiO2 interface are well-known. Extrapolation of these results shows that one dangling bond is enough to kill the luminescence of the crystallites. In the second part, we describe a calculation of a phonon assisted Auger recombination process. This turns out to be efficient, in the nanosecond to 10 picosecond range for small crystallites, which is shown to explain several experimental observations on nanostructures. Finally, we concentrate on hot carrier relaxation processes. We first discuss the predicted existence of a phonon bottleneck for small crystallites which is an intrinsic effect limiting their optical properties. We end up this section by reviewing different processes which can overcome this limitation, again based essentially on Auger processes or capture on point defects followed by re-emission.

This chapter outlines those methods for assessing root systems structure and function in the field which are based on washing roots free from the soil in which they grew. Some of these methods are included in previous reviews (Kolesnikov 1971; Bohm 1979). The methods are either disruptive or totally destructive to the root system being studied and to the immediate environment (Taylor et al. 1991).

This paper aims to contribute to a better understanding of simulation applications. To concretise the topic, modelling approaches of the spreading of a contamination plume in groundwater, the radial symmetric flow towards an auger hole and an activated carbon fdter simulation are presented. Common to all examples is the flow property - the porous medium.

The Pierre Auger Observatory Project is designed to collect a large number of cosmic rays of highest energy (above 1019 eV), whose origin is yet unknown. The atmospheric showers are observed through the combination of fluorescence detectors and a large ground array of Cerenkov water tanks. Neutrino interactions above 1017 eV could also be extracted from background at large zenith angles.

Interferometric time-resolved photoemission is used to measure the decoherence of d-bands in copper. Temperature dependence of the decoherence times gives the hole lifetime of 24 ± 3 fs for the X5 point (top-of-the d-bands) due to the Auger decay, and an electron-phonon mass enhancement factor λ = 0.20 ±0.01.

A simple approximation for charge transfer probability in time-dependent Hamiltonians is proposed with the use of the Mahanthappa-Baksi-Keldysh Green function. The Auger process and the resonant tunneling process are both considered. We show that the approximation interpolates between the limit of fast ion motion and that of slow ion motion. Also shown is that the range of validity is quite wide in Auger processes. The similar procedure is applied for the resonant tunneling process, leading to the interpolation formula for the two limits. By using model time-dependences, we also discuss the validity of our approximation.

Adsorption of SO2 on stoichiometric TiO2(110) at 153K has been studied by electron stimulated desorption (ESD). At this temperature the coverage of SO2 estimated from complementary Auger studies is about 0.27 ML Following SO2 dosing, the ESD O+ ion yield is enhanced for electron energies above 155 eV and 225 eV, and is identified with excitation of the S 2p and 2s core levels. The clean surface has a O+ threshold at 35 eV corresponding to excitation of the Ti 3p level. Changes in ion yield with substrate temperature up to 450 K are described within a model consistent with a recent NEXAFS study which revealed the surface reaction sequence: SO2→SO2− 3 →SO2− 4.

Ultrathin epitaxial NaCl(100) films on Ge(100) are ideally suited for adsorption studies on insulators using conventional surface techniques. By means of TPD, XPS, UPS, and XAES we have investigated the kinetic and electronic properties of different adsorbates like SF6, Xe, and CO2. Only physisorption is observed and hence low substrate temperatures (< 90 K) are required. Layer growth mode, desorption kinetics, and adsorbate orientation (for CO2) are dependent on the adsorbate and on the preparation parameters. The thickness of the NaCl layer strongly influences both the probability for radiation-induced dissociation of SF6 and the relative intensity of two different decay channels arising from different Auger initial states one of which is due to charge transfer screening.

Auger photoelectron coincidence spectroscopy provides an opportunity to study the origin and dynamics of Auger and photoelectron transitions. In such experiments, Auger electrons are only counted when the coincident photoelectron has also been detected. It is a difficult experiment in the solid state as there are large backgrounds due to secondary electrons that must be discriminated against. This can only be done with very good timing resolution and practical spectrometers to date have had low count rates. However, the insight into the processes afforded by the technique make it worthwhile. The technique has been demonstrated on a number of transition metals surfaces where it has shown detail of some of the complexity of the processes occurring. A short review of some of the significant experiments in the area is presented along with the data and analysis of some recent work.

In this study we observe that the positions of Auger signals shift from slightly below (∼10 eV) the tabulated values to well above (>150 eV). The observed shifts can be understood by a simple model of surface charging based on the change in the secondary electron emission of the damaged region.

We have investigated the electronic structure and electron correlation effects of gas phase and solid C60 by C Is photoabsorption, photoelectron, and Auger spectroscopies. Direct in situ comparison between C Is absorption spectra taken in the gas phase and in the solid reveals a close similarity between the unoccupied levels of the two phases. The same is true for the shake up satellites in the C Is XPS spectrum. The satellite due to plasmon excitations, on the other hand, appears at about 6 eV higher binding energy in the gas phase than in the solid, due to the contribution of higher multipole moments. Solid state effects play only a minor role in this new material, and electron correlation effects are predominantly intra molecular.

Auger electron spectroscopy (AES) is a widely used technique for the analysis of surfaces, and it has application in many fields of materials science. AES is highly surface specific, and for most materials it is only sensitive to the top few monolayers. Minute amounts of material at the surface can be analyzed. Under the right conditions 10−3 of a monolayer [6.1], and in an Auger microscope as few as 104 atoms, with a spatial resolution of 20 nm can be detected [6.2]. The qualitative interpretation of AES spectra is straightforward for many materials, and all elements except for hydrogen and helium are detectable. Any radiation with sufficient energy to ionize an atomic core level will stimulate Auger electron emission, but, by convention, AES is normally understood to use an electron beam.

It is well known that energetic electron beams strongly interact with adsorbates. As a consequence, adsorbates can dissociate and a variety of charged and uncharged species can either be desorbed or stay at the surface [1]. Metal surfaces in particular are known to stabilize electronically excited species [2]. Dissociative decays involving Auger transitions are very fast and may lead to stabilization of the adsorbates rather than to desorption.

Relativistic Auger rate calculations in intermediate coupling are presented for the Kr L3-MM spectra. Beyond the MCDF-model final-state interchannel interactions are taken into account.

Lowest-order QED theory using distorted wave states provides a convenient description for many electron scattering processes involving highly charged atomic ions. We apply QED theory to calculate ionization, excitation, and dielectronic recombination cross sections for electron scattering from highly charged uranium ions. For ionization and dielectronic recombination we compare theory with recent heavy ion accelerator measurements. We also apply lowest-order electroweak gauge theory using distorted wave states to examine the Z-scaling of parity-violating neutral current contributions to the KLL Auger decay of atomic ions.

Low and high resolution X-ray spectra of the Kα satellites emitted from Multi Charged Ions (MCIs) in collisions with surfaces at variable vertical velocity allow for the first time to differentiate between X-rays emitted from ions inside the bulk and from ions experiencing a pure surface interaction. Another proof for the bulk interaction at high vertical velocity is the first observation of the two electron - one photon double Kα ( or Kαα) emission with low energy MCIs. Auger-electron spectra emitted from hydrogenlike MCIs approaching a surface at very low velocities unveil new aspects of the atomic dynamics in front of the surface which may require the revision of previous models.

Desorption of ions and neutrals from surfaces under low energy (a few keV) electron or photon irradiation has long been recognized as due to electronic excitations not only from the outer valence levels involved in the bonding, but also from the inner levels. The latter observation goes back to the work of Knotek and Feibelman [1]. In the original formulation of the model proposed by these Authors (KF model), the states leading to desorption are generated via inter-atomic Auger transitions following core ionizations. As such, the model is strictly applicable only to maximal valency ionic compounds, that is when the cation is nominally ionised down to the noble gas configuration. However, it was soon recognized that possible desorptive states can be generated via Auger transitions in covalent systems too [2]: intra-atomic transitions are involved and correlated final state valence holes are required to make Auger Induced Desorption effective in this case [3].

We report ESD of singly- and multiply-charged substrate species (Si+, Si2+, Si3+, O+, O2+, and SiO+) and adsorbed species (H+ and F+) from thermally grown SiO2 and from quartz. We have measured ion yields Y(E) and energy distribution curves (EDCs) for electron energies E between 100 and 5000 eV. Y(E) curves have onsets related to the Si2p and O1s thresholds, but do not follow core ionization cross sections. EDCs of Si ions are a few eV wide, while those of O+ and H+ have tails extending to >25 eV. The results suggest ESD is initiated by Auger decay from a core hole in the presence of additional electronic excitations.

Auger-electron spectroscopy (AES) has developed to a major tool for chemical identification and for characterization of solid surfaces. As first emphasized by Lander[1], it can also be used a spectroscopy for gaining information on occupied electron states and their interactions. However, AES gives a far less direct picture of the occupied states than does, for example, angle-resolved photoemission spectroscopy. Owing to the broad selection rules, Auger spectra sample large classes of one-electron states, and the interpretation is also complicated by possible effects of the interparticle interaction and of the surface. I will here try to convince the reader that Auger spectra from sp-bonded materials can nevertheless be fairly well understood using conceptually rather simple models. I will, however, also emphasize the need of realistic evaluations of such models in order to verify that they contain the correct physical mechanisms. A large part of this review will be focused on recent, yet unpublished work by the Lund group.

The desorption of ions induced by electronic transitions involving core levels has been studied intensively during the last decade (1). It is well recognized that Auger decay is an important mechanism to produce active states for ion desorption in ionic as well as covalent compounds (2). However, it is also clear that the ion desorption yield induced by core excitation is not proportional to the total core hole production rate (3). Therefore a detailed analysis of initial excited states, their decay channels and the corresponding final states is needed for further progress towards a comprehensive knowledge of the basic mechanisms and possible applications of photon and electron stimulated ion desorption (PSD and ESD). The present study is intended to provide an example of such an analysis.

The main mechanism responsible for the emission of singly charged ions from ion-sputtered solid samples is known as the “surface excitation”, that is the electronic excitation of the outgoing particle during its separation from the target [1–3]. At a given velocity, such a process is governed by the electronic structure of the surface near the ejection point, and therefore is very sensitive to the local environment [4,5] . However the surface excitation model cannot explain the emission of multiply charged ions from light elements. In fact, to account for secondary ion emission from light metals, JOYES [6] early proposed a collisional mechanism where ionization results from Auger decay of collision-induced L-shell excitations and which is well supported by the observation of Auger electrons under ion bombardment [7].