Molecular-orbital X-rays and their anisotropies in heavy-ion collisions in solids and gases

Molecular-orbital spectra and anisotropies were measured in Cl+NaCl, Cl+KCl, Cl +Ti, and Cl+Ar collisions at bombarding energies between 0.5 and 2.6MeV/a.m.u. The results suggest that at low bombarding energies MO x-rays in the KCl and NaCl targets are partly produced by a two-collision process. Qualitative differences between the anisotropies of gas- and solid-target induced MO x-ray spectra underline this result. Also, new information on the bombarding-energy dependency of anisotropies at higher projectile velocities has been obtained, confirming previous observations in low-Z systems.     

The determination of subshell photoionization cross-sections in some solids and gases using photoelectron spectroscopy

Relative subshell photoionization cross-sections have been measured directly for solid samples of Sodium Fluoride and Sodium Chloride by the technique     

A high resolution ESCA instrument with X-ray monochromator for gases and solids

A new ESCA instrument with a fine-focussing X-ray monochromator, a high power electron gun, a rotating anode and a computerized multi-detector system is described. The instrument is suitable for the study of both solids and gases. The improved performance of the instrument is illustrated by a number of new spectra. Thus, spectra of gold, neon, methane, air, trifluoroacetate, thiophene and carbonyl sulphide, carbon monoxide, nitrogen, benzene and trithiapentalene are reported.     

A high resolution ESCA instrument with X-ray monochromator for gases and solids

A new ESCA instrument with a fine-focussing X-ray monochromator, a high power electron gun, a rotating anode and a computerized multi-detector system is described. The instrument is suitable for the study of both solids and gases. The improved performance of the instrument is illustrated by a number of new spectra. Thus, spectra of gold, neon, methane, air, trifluoroacetate, thiophene and carbonyl sulphide, carbon monoxide, nitrogen, benzene and trithiapentalene are reported.     

Use of a hollow cathode for determining gases in solids by the isotope balancing method

A method for the spectral isotopic determination of gases in solids has been developed. The technique involves the use of a discharge tube of the hot hollow-cathode type with two graphite cathodes. Melting of the specimen for the purpose of isotope balancing takes place in one of the cathodes and excitation of the gas luminescence before and after equalization of the isotope composition takes place in the other. A special device makes it possible to introduce the specimen into the isotope balancing zone without interfering with the vacuum. The mode of source operation and the conditions of isotope balancing and spectrum excitation are investigated.     

Integrated approach to the electronic interaction of swift heavy ions with solids and gases

The two most prominent processes of ion-matter interaction are the energy loss and charge exchange, whereby the first depends on the charge state of the ion as determined by the latter. However, up to now there has existed no closed calculation of these two major processes. We herewith present, within an integrated approach, a Monte Carlo calculation which intrinsically entails target ionization/excitation, as well as charge exchange and projectile ionization/excitation on equal footing, especially extended to the situation of ion-solid interaction.     

The physical interaction of gases with crystalline solids: III. Heat capacity and the localized-to-mobile transition

Computed heat capacities for a system of isolated atoms adsorbed on either the exposed (100) or the (111) face of a face-centered-cubic crystal are reported here. Classical statistical mechanics was used to calculate the heat capacities from a gas-solid interaction potential that was assumed to be given by a sum of pair-wise Lennard-Jones (12?6) energies over all the atoms of the solid. Results of this work are compared with a similar calculation due to Hill, who utilized a much cruder representation of the gas-solid energy. The present calculations yield heat capacities that go through a maximum in all systems considered; the temperatures of the maxima occur very near to $\text{V}{}_0\text{5k}$, where V₀ is the barrier to translation (in agreement with Hill's conclusion), but the heights of the maxima vary from system to system (in disagreement with Hill's findings). Reasons for the differences between this calculation (and one due to Van Dongen) and that of Hill are discussed.     

Nucleation of solids in solids: ferrites and martensites

When a solid such as iron is cooled across a structural transition, its final microstructure depends sensitively on the cooling rate and the depth of quench. For instance, an infinitesimally slow cooling or a shallow quench results in an equilibrium "ferrite," while a rapid cooling or a deep quench gives rise to a metastable twinned "martensite." In this paper, we arrive at a single formalism which qualitatively describes the transformation to both a ferrite and a martensite. Fundamental to this understanding is our identification of the crucial dynamical role played by nonelastic degrees of freedom in determining the final microstructure of the product solid.     

The physical interaction of gases with crystalline solids: I. Gas-solid energies and properties of isolated adsorbed atoms

It is shown that the potential energy of a gas atom interacting with a solid having a surface made up of single type of exposed lattice plane can be expressed as a Fourier series in the position variables in the plane parallel to the surface. Assuming that the total interaction is a pair-wise sum of gas atom-solid atom terms, an analytic expression for the Fourier coefficients is obtained for inverse power law interactions that is a generalization of an earlier result of Hove and Krumhansl. Gas-solid potentials calculated for several surface lattices by direct summation are compared with those given by the truncated Fourier series, and it is concluded that a satisfactory representation of the energy is obtained even when the number of terms included is small. The truncated series is then utilized to calculate Henry's Law adsorption constants and average energies for an isolated adsorbed atom. These results are compared with calculations based on completely localized and perfectly mobile adsorption models.     

Detonation in gases

We review recent progress in gaseous detonation experiment, modeling, and simulation. We focus on the propagating detonation wave as a fundamental combustion process. The picture that is emerging is that although all propagating detonations are unstable, there is a wide range of behavior with one extreme being nearly laminar but unsteady periodic flow and the other chaotic instability with highly turbulent flow. We discuss the implications of this for detonation propagation and dynamic behavior such as diffraction, initiation, and quenching or failure.     

Photoinjection of hydrogen in solids

The process of the injection of hydrogen in various solids by means of illumination was investigated. The mechanism of the process and the influence of various parameters on its efficiency have been investigated. This process has been studied for solids in which the photoinjection of hydrogen leads to drastic changes of the electrical, optical, structural, chemical, and other parameters. The objectives and possible areas of research of the phenomenon are discussed. Paper presented at the 5th Euroconference on Solid State Ionics, Benalmádena, Spain, Sept. 13–20, 1998.     

Magnetoplastic effects in solids

This paper is an overview of the studies into the effect of weak magnetic fields on the structure and mechanical properties of nonmagnetic solids of various nature (ionic, covalent, molecular, and metallic crystals, polymers, etc.). The various effects and aftereffects initiated by static, pulsed, and microwave magnetic fields that have been discovered over the past 15 years are classified and critically analyzed. The thermodynamic and kinetic aspects of the magnetic-field sensitivity of real solids with structural defects containing paramagnetic centers (electrons, holes, radicals, excitons, etc.) are discussed. Possible mechanisms for the effect of a weak magnetic field on the defect structure of crystals are considered. Special attention is given to the most developed chemical-physical theory of spin-dependent reactions between mobile particles and unpaired electrons. Interpretation of magnetoplastic effects is proposed in terms of the spin, electron, molecular, and dislocation dynamics of the complex multistage processes initiated by a magnetic field in a system of metastable structural defects.     

Resonance CARS in solids

Summary Solid-state resonance CARS spectroscopy is applied to investigate the vibronic properties of polydiacetylene chains and of the permanganate ion. Results are presented for single crystals of the symmetrically substituted diacetylene FBS where few polymer chains are embedded in the host lattice built by the monomers and for the permanganate ion doped in potassium perchlorate single crystals. Particularly, spectra of the C=C and the C≡C stretching vibrations of the polymer chains and of the fully symmetric ν₁-breathing mode of the permanganate ion, recorded for different pump laser frequencies, have been investigated. For the polydiacetylenes a theoretical model is introduced which describes the excitation and line profiles. The model is based on a crude Born-Oppenheimer approximation. The electronic wave functions are calculated by means of an LCAO-MO method in the Hückel approach. The Franck-Condon integrals are calculated under the assumption of harmonic potential functions. The simulation of the CARS spectra is based on results of calculations of absorption and resonance Raman spectra obtained from the diacetylene single crystals. Paper presented at the “XI European CARS Workshop?, Florence, Italy, 23–25 March, 1992.     

固体灾变性破坏现象

固体灾变性破坏现象多年来一直备受关注,由于其复杂性,固体灾变性破坏问题一直是力学中的典型难题之一.文章结合岩石类介质的实验观测,讨论了非均匀脆性介质灾变性破坏现象的复杂性,介绍了发展有关统计理论的初步尝试和所面临的难题,并探讨了预测灾变性破坏的可能方案.     

Positronium atom in solids

The angular distribution of annihilation 's in quartz shows that the half-width of the narrow component of the correlation curves depends on the state of aggregation (whether the substance is a single crystal, a powder, or a glass). Before annihilation, the positronium atoms may be captured by defects (vacancies, pores, or regions of reduced electron density); if this is true, the half-width of the narrow component and the long positron lifetime depend on the characteristics of the defects or traps. The sizes of the defects in certain solids (quartz glass; powdered beryllium, magnesium, and aluminum oxides; and polytetrafluoroethylene) are evaluated from the experimental half-width of the narrow component and the long positron lifetime.Translated from Izvestiya VUZ. Fizika, No. 5, pp. 59–64, May, 1971.     

Universal decoherence in solids

Symmetry implications for the decoherence of quantum oscillations of a two-state system in a solid are studied. When the oscillation frequency is small compared to the Debye frequency, the universal lower bound on the decoherence due to the atomic environment is derived in terms of the macroscopic parameters of the solid, with no unknown interaction constants.