Search

The ATLAS detector is installed in its experimental cavern at Point 1 of the CERN Large Hadron Collider. During Run 2 of the LHC, a luminosity of ℒ = 2 × 1034 cm-2 s-1 was routinely achieved at the start of fills, twice the design luminosity. For Run 3, accelerator improvements, notably luminosity levelling, allow sustained running at an instantaneous luminosity of ℒ = 2 × 1034 cm-2 s-1, with an average of up to 60 interactions per bunch crossing. The ATLAS detector has been upgraded to recover Run 1 single-lepton trigger thresholds while operating comfortably under Run 3 sustained pileup conditions. A fourth pixel layer 3.3 cm from the beam axis was added before Run 2 to improve vertex reconstruction and b-tagging performance. New Liquid Argon Calorimeter digital trigger electronics, with corresponding upgrades to the Trigger and Data Acquisition system, take advantage of a factor of 10 finer granularity to improve triggering on electrons, photons, taus, and hadronic signatures through increased pileup rejection. The inner muon endcap wheels were replaced by New Small Wheels with Micromegas and small-strip Thin Gap Chamber detectors, providing both precision tracking and Level-1 Muon trigger functionality. Trigger coverage of the inner barrel muon layer near one endcap region was augmented with modules integrating new thin-gap resistive plate chambers and smaller-diameter drift-tube chambers. Tile Calorimeter scintillation counters were added to improve electron energy resolution and background rejection. Upgrades to Minimum Bias Trigger Scintillators and Forward Detectors improve luminosity monitoring and enable total proton-proton cross section, diffractive physics, and heavy ion measurements. These upgrades are all compatible with operation in the much harsher environment anticipated after the High-Luminosity upgrade of the LHC and are the first steps towards preparing ATLAS for the High-Luminosity upgrade of the LHC. This paper describes the Run 3 configuration

This paper presents the electron and photon energy calibration obtained with the ATLAS detector using 140 fb−1 of LHC proton-proton collision data recorded at √s = 13 TeV between 2015 and 2018. Methods for the measurement of electron and photon energies are outlined, along with the current knowledge of the passive material in front of the ATLAS electromagnetic calorimeter. The energy calibration steps are discussed in detail, with emphasis on the improvements introduced in this paper. The absolute energy scale is set using a large sample of Z-boson decays into electron-positron pairs, and its residual dependence on the electron energy is used for the first time to further constrain systematic uncertainties. The achieved calibration uncertainties are typically 0.05% for electrons from resonant Z-boson decays, 0.4% at ET ∼ 10 GeV, and 0.3% at ET ∼ 1 TeV; for photons at ET ∼ 60 GeV, they are 0.2% on average. This is more than twice as precise as the previous calibration. The new energy calibration is validated using J/ → ee and radiative Z-boson decays. © 2024 Institute of Physics. All rights reserved.

This paper presents the electron and photon energy calibration obtained with the ATLAS detector using 140 fb−1 of LHC proton-proton collision data recorded at √s = 13 TeV between 2015 and 2018. Methods for the measurement of electron and photon energies are outlined, along with the current knowledge of the passive material in front of the ATLAS electromagnetic calorimeter. The energy calibration steps are discussed in detail, with emphasis on the improvements introduced in this paper. The absolute energy scale is set using a large sample of Z-boson decays into electron-positron pairs, and its residual dependence on the electron energy is used for the first time to further constrain systematic uncertainties. The achieved calibration uncertainties are typically 0.05% for electrons from resonant Z-boson decays, 0.4% at ET ∼ 10 GeV, and 0.3% at ET ∼ 1 TeV; for photons at ET ∼ 60 GeV, they are 0.2% on average. This is more than twice as precise as the previous calibration. The new energy calibration is validated using J/ → ee and radiative Z-boson decays. © 2024 Institute of Physics. All rights reserved.

The synthesis and characterization of three novel HTMs with different highest occupied molecular orbital (HOMO) energy levels and their performances in MAPbI3-based devices in comparison with Spiro-OMeTAD is reported. Without systematic optimization, the HTMs performed well. The devices delivered fill factors comparable to the one with Spiro-OMeTAD but suffered from short-circuit current. Interestingly, despite the significant differences in HOMO energy levels, all three HTMs generated the same open-circuit voltage (VOC). We explored the performance limiting factors of the HTMs by simple transient photovoltage/photocurrent (TPV/TPC) measurements along with Drift-diffusion simulations. We found no correlation between HOMO energy levels of the HTMs and VOC of the devices. Performances of the devices are limited by high trap density as well as low carrier mobility of the HTMs, and by the shunts present in the devices. Furthermore, the high trap density and low carrier mobility of the HTM are found to induce ion migration effect in the device causing slow decaying components in TPV/TPC . Nevertheless, it is confirmed that JSC and VOC, measured at steady state, are not influenced by the ion migration effect. These HTMs can be improved further by optimizing their conductivity, trap density, morphology, and can be used as alternatives to Spiro-OMeTAD or other expensive, synthetically challenging HTMs. The simple and inexpensive approach presented in this work can also be applied for effectively evaluating charge transporting materials for perovskite solar cells, European Research Council, MINECO, Comunidad de Madrid, Depto. de Química Orgánica, Fac. de Ciencias Químicas, TRUE, pub

The lack of electrocatalysts for the formate oxidation reaction (FOR) hampers the deployment of direct formate fuel cells (DFFCs). To overcome this limitation, herein, we detail the production of palladium hydride particles supported on C2N (PdH0.58@C2N) via a facile method. PdH0.58@C2N displays excellent FOR performance, reaching current densities up to 5.6 A·mgPd–1 and stable cycling and chronoamperometric operation. The Pd lattice expands due to the hydrogen intercalation. Besides, an electronic redistribution associated with the distinct electronegativity of Pd and H is observed. Both phenomena modify the electron energy levels, enhancing the activity and stability of the composite catalyst. More specifically, differential functional theory calculations show H intercalation to downshift the Pd d-band center in Pd0.58@C2N, weakening adsorbate binding and accelerating the FOR rate-determining step.

Tin diselenide (SnSe2) is a layered semiconductor with broad application capabilities in the fields of energy storage, photocatalysis, and photodetection. Here, we correlate the physicochemical properties of this van der Waals semiconductor to sensing applications for detecting chemical species (chemosensors) and millimeter waves (terahertz photodetectors) by combining experiments of high-resolution electron energy loss spectroscopy and X-ray photoelectron spectroscopy with density functional theory. The response of the pristine, defective, and oxidized SnSe2 surface towards H2, H2O, H2S, NH3, and NO2 analytes was investigated. Furthermore, the effects of the thickness were assessed for monolayer, bilayer, and bulk samples of SnSe2. The formation of a subnanometric SnO2 skin over the SnSe2 surface (self-assembled SnO2/SnSe2 heterostructure) corresponds to a strong adsorption of all analytes. The formation of non-covalent bonds between SnO2 and analytes corresponds to an increase of the magnitude of the transferred charge. The theoretical model nicely fits experimental data on gas response to analytes, validating the SnO2/SnSe2 heterostructure as a suitable playground for sensing of noxious gases, with sensitivities of 0.43, 2.13, 0.11, 1.06 [ppm]−1 for H2, H2S, NH3, and NO2, respectively. The corresponding limit of detection is 5 ppm, 10 ppb, 250 ppb, and 400 ppb for H2, H2S, NH3, and NO2, respectively. Furthermore, SnSe2-based sensors are also suitable for fast large-area imaging applications at room temperature for millimeter waves in the THz range. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

The features of the domain patterning in thin lithium niobate crystals were studied. It was shown that decrease in crystal plate thickness led to domain size increase due to limitation of forward growth. The domain size weakly depended on electron energy due to equality of screening charge value at the same doses and various accelerating voltages. The weak dependence of domain sizes on pattern period was attributed to absence of electrostatic interaction of domain walls. The possibility of creation of the through periodical domain structures with the vertical domain walls and period down to 2 μm in thin crystal was demonstrated. © 2019, © 2019 Taylor & Francis Group, LLC.

The work describes an investigation of afterglow of various luminophores under influence of pulsed X-ray radiation of nanosecond duration. As a source of radiation a pulsed X-ray "Yasen 01" apparatus is applied. Maximum impulse current of an X-ray tube is 300 A. Maximum electron energy is 120 keV. Half-height pulse duration of an X-ray burst is about 30 ns. A pulse repetition rate is up to 4 kHz. Two types of X-ray luminophores based on gadolinium oxysulfide Gd 2 O 2 S:Tb and cesium iodide CsI:Tl have been investigated. The novelty of the work is use of a fast-acting solid-state semiconductor photomultiplier. It allows recording changes of luminophores luminosity in the nanosecond time range. The photomultiplier is characterized by having two discreet outputs for measuring quickly and slowly time-changing light flows. Presence of two signal outputs allows recording changes of luminophores luminosity both during fast nanosecond excitation and during long-time afterglow. Obtained data about the nature of afterglow of investigated luminophores makes it possible to select the best one for use in conjunction with a pulsed X-ray apparatus with a high pulse repetition rate. © Published under licence by IOP Publishing Ltd.

The irradiation exposure experiments were carried out by means of the pulsed repetitive nanosecond accelerator URT-0.5 (electron energy of up to 500 keV, a pulse width of 50 ns, pulse repetition rate of up to 200pps). The determination of the distribution of the absorbed dose (AD) in the depth in the polyethylene was conducted by a gray wedge. The measurement of the electron beam AD on the surface of the shell (removed from the eggs) and under the shell, as well as beneath the absorber layer (polyethylene 80 microns thick) was also performed by the film dosimeter. Thermoluminescent dosimeters, TLD-500, were used to determine the distribution of the bremsstrahlung AD inside chicken eggs. These results lead to the conclusion that the irradiation of an electron beam with the AD level of 5 kGy is sufficient for complete disinfection on the surface of an egg. The AD inside of it will not exceed 8 cGy because of bremsstrahlung. © RAD Conference Proceedings. All rights reserved.

A comprehensive study of atomic-layer deposited thulium oxide (Tm2O3) on germanium has been conducted using x-ray photoelectron spectroscopy (XPS), vacuum ultra-violet variable angle spectroscopic ellipsometry, high-resolution transmission electron microscopy (HRTEM), and electron energy-loss spectroscopy. The valence band offset is found to be 3.05±0.2eV for Tm2O3/p-Ge from the Tm 4d centroid and Ge 3p3/2 charge-corrected XPS core-level spectra taken at different sputtering times of a single bulk thulium oxide sample. A negligible downward band bending of ∼0.12eV is observed during progressive differential charging of Tm 4d peaks. The optical band gap is estimated from the absorption edge and found to be 5.77eV with an apparent Urbach tail signifying band gap tailing at ∼5.3eV. The latter has been correlated to HRTEM and electron diffraction results corroborating the polycrystalline nature of the Tm2O3 films. The Tm2O3/Ge interface is found to be rather atomically abrupt with sub-nanometer thickness. In addition, the band line-up of reference GeO2/n-Ge stacks obtained by thermal oxidation has been discussed and derived. The observed low reactivity of thulium oxide on germanium as well as the high effective barriers for holes (∼3eV) and electrons (∼2eV) identify Tm2O3 as a strong contender for interfacial layer engineering in future generations of scaled high-κ gate stacks on Ge., QC 20150629

Self-assembled monolayers and multilayers of a noradrenaline analogue (Nor-Pt) on gold substrates as well as multilayers of noradrenaline have been investigated by means of the molecular orientation, the molecule-surface interaction, the molecular composition and the functional group availability for further biointeraction processes, using X-ray photoelectron spectroscopy (XPS), infrared reflection-absorption spectroscopy (IRAS), and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. A chemical shift (1.7 eV) of the S 2p peak to lower binding energies is observed, in the XPS spectrum, indicating that the Nor-Pt molecules are chemisorbed onto the gold substrate. The IR results show that Nor-Pt adsorbate has the C=O stretching vibration modes parallel oriented relative to the gold substrate. The average tilt angle of the aromatic ring relative to the gold surface normal is determined to be approximately 51°, based on the NEXAFS measurements on Nor-Pt monolayers. The experimental results and assignments are supported with theoretical studies where we use the building block principle in the spectral analysis and compare with the measurements of noradrenaline and Nor-Pt. The theoretical calculations are shown to be useful; for angle dependence NEXAFS studies as resonances with fully φ* or σ* character are preferred for correct analysis., QC 20161222

Magnetic properties of carbon nanotubes (CNT) obtained by plasma-enhanced chemical vapour deposition (PECVD) have been studied. The growth of these nanotubes has been activated from Ni catalyst nanoparticles. Samples consist of Ni nanoparticles encapsulated at the tip of vertically aligned multiwalled carbon nanotubes (VACNTs) forming an homogeneous and dense large area monolayer of isolated (non-contacting) nanoparticles. The magnetic characterisation has been performed in the temperature range of 5-300 K with magnetic fields up to 9 T. The results show that the wide size range (30-180 nm) of the particles originates the coexistence of blocked and superparamagnetic particles and leads to the strong ferromagnetic behaviour of the whole assembly. The coercivity decreases monotonically with increasing temperature and the value for the intrinsic coercivity is 225 Oe. The encapsulation of Ni nanoparticles by VACNTs preserves them from aggregation. This makes possible to tune the coercivity by controlling size distribution of particle monolayers. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electron energy loss spectroscopy (EELS) is used to study the transition from the buffer layer to the first graphene layers during graphitization of SiC(0001). Graphene growth is controlled and correlated with spot profile analysis in low energy electron diffraction and x-ray photoelectron spectroscopy. In the EELS data both electronic transitions and plasmon losses are sensitive to the interface. The collective in-plane excitations show a characteristic blueshift upon graphitization, while single electron transitions with dipole moments along the surface normal are suppressed for the buffer layer. These dependencies can be used to control the number of epitaxially grown graphene layers. © 2009 American Institute of Physics.

We study the flavor-changing-neutral-current process c -> u mu(+)mu(-) using 1.3 fb(-1) of p (p) over bar collisions at root s = 1.96 TeV recorded by the D0 detector operating at the Fermilab Tevatron Collider. We see clear indications of the charged-current mediated D-s(+) and D+->phi pi(+)->mu(+)mu(-)pi(+) final states with significance greater than 4 standard deviations above background for the D+ state. We search for the continuum neutral-current decay of D+->pi(+)mu(+)mu(-) in the dimuon invariant mass spectrum away from the phi resonance. We see no evidence of signal above background and set a limit of B(D+->pi(+)mu(+)mu(-))< 3.9 x 10(-6) at the 90% C.L. This limit places the most stringent constraint on new phenomena in the c -> u mu(+)mu(-) transition., QC 20110429

The use of two truly two-dimensional gapless semiconductors, monolayer and bilayer graphene, as current-carrying components in field-effect transistors (FETs) gives access to special types of nanoelectronic devices. Here, we report on the development of graphene-based FETs containing two decoupled graphene monolayers manufactured from a single one folded during the exfoliation process. The transport characteristics of these devices differ markedly from those manufactured from a single-crystal bilayer. By analyzing Shubnikov-de Haas oscillations, we demonstrate the possibility to independently control the carrier densities in both layers using top and bottom gates, despite there being only a nanometer scale separation between them. © 2008 American Institute of Physics.

We study intrinsic spin Hall effect in p-type GaAs quantum well structure described by Luttinger Hamiltonian and a Rashba spin-orbit coupling arising from the structural inversion symmetry breaking. The Rashba term induces an energy level crossing in the lowest heavy hole subband, which gives rise to a resonant spin Hall conductance. The resonance may be used to identify the intrinsic spin Hall effect in experiments. © 2006 The American Physical Society.

We study intrinsic spin Hall effect in p-type GaAs quantum well structure described by Luttinger Hamiltonian and a Rashba spin-orbit coupling arising from the structural inversion symmetry breaking. The Rashba term induces an energy level crossing in the lowest heavy hole subband, which gives rise to a resonant spin Hall conductance. The resonance may be used to identify the intrinsic spin Hall effect in experiments. © 2006 The American Physical Society.

We study intrinsic spin Hall effect in p-type GaAs quantum well structure described by Luttinger Hamiltonian and a Rashba spin-orbit coupling arising from the structural inversion symmetry breaking. The Rashba term induces an energy level crossing in the lowest heavy hole subband, which gives rise to a resonant spin Hall conductance. The resonance may be used to identify the intrinsic spin Hall effect in experiments. © 2006 The American Physical Society.

High-resolution C(1s) near-edge X-ray absorption and X-ray photoionization spectra of the free biphenyl molecule are presented and theoretically analyzed in order to allow an assignment of the observed spectral features. Finite lifetime broadening, a high density of vibrational states, and a strong overlap of contributions from chemically different carbon atom sites only partially allow resolving the vibrational fine structure. However, the shape and width of the spectral profiles are strongly determined by both chemical shifts and vibronic effects. In particular, different from photoionization of valence levels, both types of core level spectra do not contain contributions from dihedral modes which are related to the twisting motion of the two phenyl rings. Contrary to naphthalene, C-H stretching modes are significantly enhanced in the core excitation spectra of biphenyl while the contributions from C-C stretching modes are reduced., QC 20100906

A straightforward approach for computing the K -edge shake-up spectra of molecules based on equivalent core-hole linear response theory at both Hartree-Fock and density functional theory levels is proposed. Benchmark calculations have been performed to explore its sensitivity to different types of functionals and basis sets for the carbon 1s shake-up spectra of benzene and metal-free phthalocyanine (H2 Pc). A very good agreement with previous theoretical and experimental works for the benzene molecule has been obtained for all the functionals and basis sets tested. Electron correlation is found to be essential for a good description of the H2 Pc system, whose experimental C 1s shake-up spectrum is best reproduced by the hybrid density functional., QC 20100915

The np sigma 1 Sigma(u)(+) and np pi (1)Pi(u) states in D-2 have been selectively excited using monoenergetic synchrotron light in the range of 13.97-15.84 eV and the subsequent dispersed emission to the EF (1)Sigma(g)(+) state was observed using a grating spectrometer. In total, 18 emission bands from the levels n = 3-6 were studied and rotationally analysed. The intensities of the P and R branches relative to the Q branch were found to vary strongly in the np pi (1)Pi(u)(+)-EF(1)Sigma(g)(+) bands indicating the existence of predissociations of np pi (1)Pi(u)(+) levels above the dissociation limit D(1s) + D(2l)., QC 20100916

The calculation of the intersubband absorption in a modulation-doped V-shaped-quantum-wire (V-QWR) is presented. The method is based on self-consistent solving of the single band Schrödinger equation in a nonparabolic approximation. Our calculation shows that the absorption spectrum is anisotropic and has two absorption peaks at 19meV and 115 meV depending on light polarization., QC 20141202

In lateral quantum dots, the combined effect of both Dresselhaus and Bychkov-Rashba spin-orbit coupling is equivalent to an effective magnetic field ±BSO which has the opposite sign for sz=±1/2 spin electrons. When the external magnetic field is perpendicular to the planar structure, the field BSO generates an additional splitting for electron states as compared to the spin splitting in the in-plane field orientation. The anisotropy of spin splitting has been measured and then analyzed in terms of spin-orbit coupling in several AlGaAs/GaAs quantum dots by means of resonant tunneling spectroscopy. From the measured values and sign of the anisotropy we are able to determine the dominating spin-orbit coupling mechanism. © 2005 The American Physical Society.

The rotational spectrum of 2-methylpyridine (alpha-picoline, CH3C5H4N) in the two lowest levels of methyl internal rotation (m = 0, +/-1) has been recorded in the frequency range from 2 to 15 GHz using a molecular beam Fourier transform microwave spectrometer. The high resolution and sensitivity of this spectroscopic technique allowed resolution of hyperfine structures due to N-14 nuclear quadrupole coupling with high accuracy and detection of the spectra of the N-15- and all C-13-isotopomers. These investigations considerably extend the results from an earlier study on the normal species (DREIZLER, H., RUDOLPH, H. D., and MADER, H., 1970, Z. Naturforsch., 25a, 25); improved rotational and centrifugal distortion constants as well as all components of the N-14 quadrupole coupling tensor have been obtained. Analysis of the spectra of the isotopomers yielded the N-14 quadrupole coupling constants X,c and chi(aa) - chi(bb) (for the C-13 species), the potential parameter V-3 for the barrier hindering the internal rotation of the methyl group, and, in particular, r(o), r(s), r(m)((1)) and r(m)((2)) structural parameters for the molecule. In addition to the microwave studies on the monomer, we have also investigated the rotational spectrum of the weakly bound dimer of normal 2-methylpyridine with Ar. The results obtained for the quadrupole coupling constants and the hindering potential for the internal methyl rotation show that the corresponding parameters are not significantly, or only slightly, changed in the complex., QC 20101130

Two recently proposed low-energy azafullerene C48N12 isomers have been theoretically characterized using x-ray spectroscopies. The x-ray photoelectron spectroscopy, the near-edge absorption fine structure, the x-ray emission spectroscopy, and the ultraviolet photoelectron spectroscopy for both isomers have been predicted at the gradient-corrected density functional theory level. These spectroscopies together give a comprehensive insight of the electronic structure on the core, valence, and unoccupied orbitals. They have also provided a convincing way for identifying the isomer structures., QC 20100929

The problem of adequate electronic model for doped manganites like La1-xSrxMnO3 remains controversial. There are many thermodynamic and local microscopic quantities that cannot be explained by the conventional double-exchange model with dominantly Mn3d location of doped holes. In such a situation we argue a necessity to discuss all possible candidate states with different valent structure of manganese and oxygen atoms, as well as different valent states of octahedral MnO6 centers. In frames of rather conventional cluster approach, crystal field and the ligand field model we address different types of MnO6 centers, different types of d-d, and charge-transfer (CT) transitions. We draw special attention to the so-called CT states related to strong intra-center charge fluctuations. As we conjecture, namely these could become active valent states for doped manganites. We discuss some electric and magnetic properties of the electron MnO610-, and hole MnO68- centers with unconventional 6A1g-6T1u and 4A2g-4T2u valent manifolds, respectively. We propose two idealized theoretical models for hole system in doped manganites. The first one implies an overall oxygen localization for the doped holes occupying the non-bonding O2p orbitals. The second assumes a doping induced formation of the electron-hole Bose liquid, or a system of the electron MnO610-, and hole MnO68- centers. In a sense, this scenario resembles a well known disproportionation reaction. In both cases one might expect non-trivial magnetic behavior with strong ferromagnetic fluctuations due to anomalously strong ferromagnetic coupling of non-bonding O2p holes with Mn3d electrons. © 2002 Elsevier Science B.V. All rights reserved.

We present resonant x-ray Raman scattering results on Sr2CuO2Cl2, a model compound for high- Tc superconductors. We demonstrate that the dd excitations can be observed and show that the polarization dependence can be used to identify the dd excitations. We find the transition from the dx2−y2 ground state to the dxy excited state at 1.35 eV and to the degenerate dxz and dyz excited states at 1.7 eV. From analysis of the polarization dependence we conclude that the d3z2−r2 orbital energy is at 1.5 eV and not in the midinfrared (0.5 eV) as recently suggested. We use recent theoretical arguments to show that the d3z2−r2 excitation is accompanied by a local spin flip resulting in a shift upwards of 0.2 eV due to the exchange interaction with the neighboring spins. ©1998 American Physical Society.

The Hartree-Fock states of the many-electron atomic system can be unstable with respect to a static or dynamic shift of the electron shells. An appropriate non-rigid shell model for atomic clusters is developed. It permits to formulate a convenient approach to the semiempirical description of the different correlation effects and to reveal some new effects.

We present an atom interferometer based on the interference of three partial matter waves in three different internal and external states. Coherent laser excitation acts as a beamsplitter to create a superposition state of the ground state and two Zeeman sublevels of the metastable state of magnesium atoms. The interference pattern of the output ports shows high contrast and the characteristics of three-beam interferences as known from optical interferometry. In comparison to two-beam interferometry a reduction of the fringe width of (32±8)% is observed. This offers various possibilities for improved measurements of quantum-mechanical phases due to the internal atomic-state sensitive coupling of external potentials. This is demonstrated for the interaction of magnesium atoms with an external magnetic field. © 1997 The American Physical Society.

The energy-dependant cross sections of the impact-excited intramolecular vibrations in an epitaxial C60(111) film have been measured by High Resolution Electron Energy Loss Spectroscopy (HREELS). A Negative Ion Resonance (NIR) behaviour is evidenced by a dramatic cross-section enhancement at a primary energy of ∼2.9 eV together with some fine structures on the high energy side. Through comparison with experimental results on the unoccupied states and on the electronic excitations of solid C60, these NIR structures can be correlated to a temporary trapping of the probing electron in the LUMO+3-derived state in the framework of an 'electronic excitation associated' NIR process. © 1995.

A review of experimental research performed on installations of GYRAC-type based on the synchrotron gyromagnetic autoresonance (SGA) phenomenon is presented. It is shown that the SGA-regime can be used to obtain relativistic plasma as well as a controlled bunch of relativistic electrons. GYRAC-produced plasma is of interest for applied plasma physics as a source of particles and different kinds of radiation (synchrotron radiation and bremsstrahlung).

Current views on Dirac's creative heritage and on his role in the formation and development of quantum physics and in shaping the physical picture of the world are discussed. Dirac's fundamental ideas in later life (1948-1984) and their current development are given considerable attention. © 2003 Uspekhi Fizicheskikh Nauk, Russian Academy of Sciences.