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The process of ionization that is due to the Migdal effect and which occurs in the elastic scattering of a heavy neutral particle, including a weakly interacting massive particle (WIMP), on a noble-gas atom in the case of its small recoil energy is considered. The mean number of primary and secondary electrons emitted in an individual event of such ionization is estimated, and the energy distributions of primary electrons are obtained. The calculations were performed for various noble-gas atoms with allowance for experimental data on their ionization by photons. [ABSTRACT FROM AUTHOR]

A method for improving the production of the radioisotope 123I in proton cyclotrons, which makes it possible to increase its technological yield by 2–3 times, is reported. For this purpose, it is proposed to introduce hydrogen into a target with 124Xe, which makes it possible to extract from it the 123I formed over the irradiation time on decay of the accumulated 123Xe. [ABSTRACT FROM AUTHOR]

Free-electron emission by stopping recoil atoms arising from particle–atom collisions in a noble-gas medium is numerically investigated using argon as an example. We demonstrate that, during propagation through matter of recoil atoms with energies over a few keV, vacancies in their internal L-shells arise via the Pauli mechanism with a probability on the order of 100%. As a result, over 30 free electrons are released upon a single interaction act in liquid or gaseous noble gas as a working medium of a particle detector. Thereby, the sensitivity of an argon-filled particle detector is significantly enhanced. In a xenon-filled detector, Pauli ionization sets in at higher recoil-atom energies of ≳100−200 keV and, therefore, is unlikely to boost the detector sensitivity to light-dark-matter particles, which are generally expected to produce recoil atoms with energies ≲10 keV. [ABSTRACT FROM AUTHOR]

A model water-filled porous medium is investigated using NMR techniques, and the results of these measurements are interpreted theoretically. A rigorous theoretical description of the near-surface layer, qualitatively introduced when interpreting the NMR data for porous materials, is formulated. Our results indicate that the thickness of the near-surface layer exceeds that quoted in the literature by several orders of magnitude. This result allows to obtain valuable information about the processes at the liquid-solid interface. [ABSTRACT FROM AUTHOR]

The process of atomic nucleus recoil under the elastic scattering of a neutral particle, a hypothetical dark matter particle (WIMP) in particular, is considered. In the case of a low-energy recoil of the nucleus, the relations between the probability of ionization of the recoil atom and the cross section of ionization of such an atom by a photon, as well as by an electron, are obtained. These expressions contain only one parameter, the values of which are calculated for different types of atoms, taking into account experimental data on ionization by photons and electrons. The probabilities of ionization of noble-gas recoil atoms are compared with the results of other theoretical studies, and it is emphasized that the proposed calculating model is quite reliable and its accuracy is determined by the error of the experimental cross sections that are used. [ABSTRACT FROM AUTHOR]

We have established the conditions for the absence of Alfvén ion-cyclotron instability in the formation and subsequent acceleration of ion rings by collapsing cylindrical plasma liners. [ABSTRACT FROM AUTHOR]

The conditions of suppressing the collective slowing-down of an ionic beam on electrons, which is caused by the excitation of electron plasma oscillations (beam instability) by ions, are found. In contrast to available explicit and implicit indications, a large spread of the energies only in an ionic beam is insufficient for this suppression. The acceleration of ions is shown to become stable when a sufficiently large spread of the electron velocities is simultaneously present. The beam instability of ions is suppressed by the Landau damping of the ion-excited plasma waves at electrons. The results obtained are used to analyze the possibility of ion acceleration by collapsed cylindrical plasma liners. [ABSTRACT FROM AUTHOR]

According to the Szilard–Chalmers effect, 99Mo recoil atoms can be obtained in nuclear reactions and recorded in a collector. Knowledge of the dependence of the yield of 99Mo atoms on the thickness of the molybdenum layer is necessary for their efficient collection. The yield of 99Mo recoil atoms from molybdenum nanolayers in the nuclear reaction 100Mo(p, x)99Mo was measured as a function of the thickness of the nanolayer. Nanolayers of metallic molybdenum were fabricated by magnetron sputtering on sapphire plates. The measurements were performed after the nanolayers were irradiated by 28 MeV protons in the U-150 cyclotron. The yield of 99Mo recoil atoms for 38–205 nm thick nanolayers was 65–8%. It was found that the maximum 99Mo yield obtains with molybdenum layer thickness 80 ± 5 nm. It was found that the free path of 99Mo recoil atoms in native metallic molybdenum is equal to 34 ± 9 nm. [ABSTRACT FROM AUTHOR]

The interaction between two slow atoms adsorbed on the surface is considered. It is shown that, similar to Efimov states of three particles, this system has a bound state at any sign of the scattering length. [ABSTRACT FROM AUTHOR]

The radionuclide 99Mo was produced and separated in the process of irradiating powdered mixtures of molybdenum compounds and buffer particles by 30 MeV protons. The separation is based on the Szilard-Chalmers effect wherein 99Mo recoil particles are fixed in inert buffer particles. Two types of targets were investigated by using mixtures: soluble molybdenum compound-insoluble buffer and insoluble molybdenum compound-soluble buffer. 99Mo yield equal to 20% with enrichment coefficient 18.3 was obtained by using a target consisting of a mixture of submicron 100MoO3 and Al2O3 particles; the 99Mo yield was equal to 20% and the enrichment coefficient 18.3. For a target with the composition 100MoS2 + KCl, making it possible to separate 99Mo recoil atoms directly into solution, the 99Mo yield was equal to 8.7% and the enrichment coefficient 30.7. [ABSTRACT FROM AUTHOR]

The main processes determining the distribution function of nonrelativistic stopping electrons in a material are analyzed. It is established that electrons change direction of their motion mainly because of scattering on nuclei of the material at small angles. This property of the Coulomb interaction is used to fasten numerical computations of the parameters of stopping electrons. [ABSTRACT FROM AUTHOR]

The quantum–classical Monte Carlo cascade calculation model for the muonic (non-hadronic) hydrogen atom has been modified for exotic pK − and $p\bar p$ atoms with strong interaction. The radiative and collision transitions were taken into account only because in such a case of “heavy” atoms the effects of exotic molecule formation are not essential. The radiative cascade was considered within the framework of quantum mechanics whereas the collisions of exotic atoms in excited states with hydrogen were described by methods of classical mechanics. The yields for the K-series X-rays in pK − and $p\bar p$ atoms have been calculated and compared with the experimental data. [ABSTRACT FROM AUTHOR]

The phenomenological vector model of water is used to clarify the nature of the percolation phase transition in hydration water films around the surface of immersed bodies, which is found in molecular dynamic calculations. The transition is explained by the emergence of ordering in the directions of projections of water dipole moments on the body surface at the lower critical temperature, i.e. by the formation of ferroelectric water film. The evaluation of this temperature is given, which is consistent with numerical calculations. [ABSTRACT FROM AUTHOR]

The motion of a system of interacting nonlinear charged oscillators is investigated numerically. Because of nonlinearity, the total collective electric field gives rise to a phasing effect—correlations in the phases of the oscillators. The consequence is superradiation—the enhanced spontaneous short-term emission of the energy stored in the oscillators. It is shown that the oscillations of the oscillators become stochastic because of the dipole-dipole interaction between them and their nearest neighbors. As a result, as the density of the oscillators increases, distant collective correlations are suppressed, superradiation ceases to be generated, and radiation is shielded in the medium. The phenomena considered in the present paper can play an important role in cyclotron emission from a plasma and thus should be taken into account in emission calculations. The process whereby the energy of the transverse electron motion in electron cooling devices decreases is analyzed as an example. This process occurs as a result of the development of cyclotron maser instability and has the nature of superradiation. The onset of correlations between individual electrons moving in their Larmor circles is the initial, linear stage of instability developing in the plasma. Superradiation is the final, nonlinear instability stage. [ABSTRACT FROM AUTHOR]

Kinetic equations are derived for the positron velocity distribution in storage rings with electron cooling. Both drag force and components of the velocity diffusion tensor are calculated. The mechanism of approach to a steady-state positron velocity distribution via electron cooling is discussed. It is shown that the resulting steady-state positron distribution is very close to the electron distribution when the magnetic field is sufficiently strong. [ABSTRACT FROM AUTHOR]

A phase transition is discussed that can occur in a plasma with substantially different transverse and longitudinal temperatures of electrons moving in a magnetic field, T⊥/T|| > 1. The Debye cloud surrounding an ion sharply contracts as T|| decreases or the magnetic field increases. The effect of larger radiative electron–ion recombination cross sections compared with their theoretical values is explained; this effect is observed in storage rings with electron cooling systems (coolers). The role played by the phase transition in the crystallization of ion beams is discussed. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

It is found that the plastic deformation of lightly doped crystalline silicon samples (N < 6×10[sup 16]cm[sup –3]) with a low compensation (K∼3×10[sup –2]) gives rise to nonohmic conduction σ[sub M] in electric fields that differs radically from conventional hopping conduction via the ground states of impurities (σ[sub 3]). The values of σ[sub M] can exceed values of σ[sub 3] by a factor of 10[sup 3]–10[sup 5]. The value of σ[sub M] and its dependence on the electric (E) and magnetic (H) fields can be controlled by varying the density of dislocations and the mode of thermal sample treatment. A strong anisotropy of σ[sub M] is observed in samples with oriented dislocations: the conductivities along and across dislocations can differ by a factor of 10[sup 4]. The results are explained by the occurrence of conduction via the H[sup –]-like states of impurities concentrated in the vicinity of dislocations. The levels of these states lie between the upper and the lower impurity Hubbard bands. © 2002 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The majority of deexcited hadronic atoms (hX) (h = K[sup -], &pmacr;, ... and X = p, d, t) are accelerated up to energies of about 100 eV due to Coulomb transitions. The diffusion model of Stark transitions is developed. The resulting nuclear capture rate is higher than that in Bethe-Leon theory by a factor not less than five. Thus, only nonaccelerated atoms can survive. Therefore, the yield Y of K[sub α] x rays is significantly less (by a factor of about ten) than that calculated in standard cascade models and is approximately equal to 0.2% and 1.0% for (K[sup -]p) atoms at hydrogen densities of N= 2 x 10[sup 21] and 5 x 10[sup 20] atom/cm³, respectively. The scheme of a more accurate calculation of Y is also presented. [ABSTRACT FROM AUTHOR]

The possibility of cyclotron maser cooling of the transverse motion of electrons in a beam with the oblate velocity distribution characteristic of the setups with electron cooling has been analyzed. [ABSTRACT FROM AUTHOR]

A response by L. I. Men'shikov to a letter to the editor about his article related to the distribution of electrons.