Electron Shells Of Atoms Research Articles

Nuclear alpha-emission—I. consistent quantum–mechanical approach in terms of collective coordinates

Alpha emitting is treated as a particular case of the nucleus decay. The classical Hamiltonian of the nuclear system is constructed, accounting for the Coulomb inner-nuclear interaction and strong interaction approximated by the "Yukava plus exponent" potential. The effective quantization in terms of the collective variable T (elongation) is performed. The effective mass, adjacent to T, depends on T and is of tensor character; its tensor character, is shown, can manifest itself in the collisional experiment as the "dependence of the potential barrier height" on the incident particle energy. The numerical calculations for 210Po show that the mass tensor character is of principal value for the spectrum of the emitted alpha-particles. The possible consequences for the secondary processes in the atomic electron shell and for the electron-positron pair production are discussed.

Kramers mechanism of indirect spin-spin couplings of nuclei in crystals

Nuclear spin exchange in the ionic clusters [Tl4Cl]3+, situated in the cavities of cation-substituted chlorosodalite, was investigated by the203Tl and205Tl NMR method. It was shown that nuclear spin exchange in the ionic crystals is realized by analogy with the Kramers mechanism of indirect exchange of electron spins using the electron shells of the bridging atoms.

Stopping Power and the Concept of Effective Ion Charge at Low Energies

A new formalism for the calculation of the ion-matter interaction phenomenon was developed by incorporating the atomic electron shell structure. This formalism allows for discrimination among the electrons of the target atoms according to their average positions with respect to the shell structure of the projectile ion. By doing so, we are able to show a strong dependence of the ion energy loss on its electron shell distribution. Thus a detailed quantum mechanical description of the moving ion is necessary to predict its precise trajectory and energy loss inside matter. The concept of an "effective charge" in the context of the electron stopping power formalism is emphasized and extended.

Understanding fully developed turbulence: Some new ideas

The present paper is a contribution within the E(∞) Cantorian space theory. After a brief review of the historical development of length and time measurements, we consider conventional definitions and methods of calculation of vector and fractal dimensions. A definition of emptiness as zero entropy is discussed.Treating the `fabric' of space-time as non-permanent, we consider other possible ways of filling emptiness. This leads to a definition of range dimension (p), the properties of which are then discussed. p=1/2 and p=1/4 range dimensions are linked to p=1 (conventional) range dimensions in fluid environments using differential velocities and accelerations. Applications of p=2 range dimensions to quantum events are also considered, and eclectic evidence for the existence of range dimensions is presented.The bijection relationship, defining space-filling fractal dimension (dc,n) is extended to cover the range 1<n<4 vector dimensions, and a physical interpretation in terms of a characteristic length ratio (ln/l0) is developed. The n-dimensional term (ln/l0)n is then closely correlated to the ratio (l1/l0)dc,n. The bijection relationship is extended to other range dimensions.An approximate empirical relationship is now presented, which provides a basis for defining conventional (p=1) range dimensional space, by introducing Nn, the number of elements needed to set up 1–4 vector dimensions. Two other ways of obtaining approximately the same number of elements are also given, one of which leads to the concept of a p=2 range dimensional substrate for conventional (p=1) range dimensions. It is found that a single track in p=1 range dimensions needs nearly p=2 range dimensions to support it. The required value then falls as n increases, equaling approximately unity for n=3 vector dimensions. A second empirical equation defining the same value of Nn for 3<n<4 vector dimensions, based on space-filling fractal dimensions for p=2 range dimensions is also presented.A fractal form for conventional space is then defined, characterised by tiny elements of negative entropy (in log space). This definition is then readily amalgamated with dynamically generated space, and the latter is shown to correlate with the classical gas equation and Hooke's law for solids. Based on the new definition of space, a proof of both the well-known inverse square law and Hubble's astronomical law is given.A relationship between the number of events in p=1andp=2 range dimensions is next established, and the effect of `information loss' corresponding to the reduction in the required value of range dimension as vector dimension (n) increases is tentatively linked to wave functions, for n=4 vector dimensions. The corresponding `useful' information is then shown to be contained in the exponent field, which is of the form {2f(e−1)pdc,4}, where f≈1,p=2 range dimensions, and e (within the exponent!) equals the numerical value of the exponent. This field is then sub-divided to various extents, and the corresponding entropies are used to determine sets of distinguishable arrangements N. These sets are successfully compared with `magic' numbers in atomic and nuclear physics, and with preferred sodium atom groupings. A prediction of the number of occupied energy levels in atomic electron shell theory is successfully carried out.Finally, combining `useful' and `hidden' information the p=2 range dimension substrate is re-created by allowing matter to collapse and `drain away' from its p=2 range dimensional space base. Light propagation through space having p=2 range dimensions is then discussed.The paper concludes with a discussion of various ideas implicit in the text, though not necessarily directly obvious. The interdependence of fractal, range and vector dimensions is first considered, followed by a review of the universal application of range dimensions. The paper ends with a study of the fractal nature of space and its justification.

Effect of atomic size on the minimum X-ray absorption coefficient in the six-beam Borrmann diffraction

The effect of the finite size of atomic electron shells on the minimum X-ray absorption of the six-beam (0 0 0, 2 2 0, 2 4 2, 0 4 4, 2 2 4, 2 0 2) Borrmann diffraction is discussed. An X-ray wave field calculation shows that the minimum photoelectric absorption in Ge by the L electrons located at a distance of r = 0.086 A ̊ from the centres of the atoms is about 2 cm −1, one hundred times higher than the absorption coefficient of 0.02 cm −1 at r = 0. We explain the absorption of the six-beam Borrmann diffraction observed experimentally using this result. Our analysis also predicts that the multiple-beam Borrmann effects should be less observable in Si and in diamond.

Nuclear excitation in the positron-atomic electron annihilation involving the intermediate nuclear states

A theoretical analysis of the excitation of the isomeric and low-lying states of nuclei by annihilation of positrons with atomic-shell electrons is presented. Resonant and inelastic excitations via intermediate nuclear states are considered. The calculation of the resonant cross section of annihilation excitation of the isomeric level of 115In gives sigma FI( epsilon +res) approximately=2.3*10-26 cm2 in agreement with experimental data.

Thomas-fermi approach to the theory of optical constants in the XUV range

The theory of many-electron atoms and ions and their interaction with XUV radiation is one of the fundamental aspects of X-ray laser physics. The topic of this paper is the theory of optical constants of many-electron atoms in the XUV which define the dielectric susceptibility of materials in this wavelength range. We use the statistical description of atomic electrons and, as a starting point, develop the rigorous theory of the dynamical response of a Thomas-Fermi atom. The equations obtained are used with proper boundary conditions to find the dynamical polarizability and photoabsorption of many-electron atoms. The results are employed for an analysis of existing experimental data on optical constants of Ar and Si. A procedure is suggested to include into the theory the effects of atomic electron shell structure. This leads to more reasonable results and better agreement with experiment. In particular, the effect of the Cooper minimum in the atomic photoionization cross-section can be described.

Laser-assisted internal conversion.

A general formula for the coefficient of internal conversion in an intense laser field, which is valid for all atomic electron shells, is deduced in a simple nonrelativistic model. For special shells, for which internal conversion without the laser is energetically forbidden but which have an energy defect relatively small compared to the laser photon energy, the presence of the laser radiation is essential. Cases such as the 4s(1/2 shell internal conversion of the E1 transition of the isomeric state $^{183}\mathrm{W}^{\mathrm{m}}$ (${E}_{\ensuremath{\gamma}}$=544 eV, \ensuremath{\tau}=5.3 s, J${=(11/2}^{+}$) and the 5d(3/2, 5d(5/2 shell internal conversions of the E3 transition of the isomeric state $^{235}\mathrm{U}^{\mathrm{m}}$ (${E}_{\ensuremath{\gamma}}$=73.5 eV, \ensuremath{\tau}=26 min, J${=(1/2}^{+}$) are numerically investigated in the small momentum approximation.

Some regularities in proton stopping cross sections

The results of recent measurements of the stopping cross sections of protons and He ions are analyzed. The dependence of the maximum value of the stopping cross section, as well as of the energy at which the maximum is reached, on the atomic number of the target atoms is shown to be in correlation with the order of sequential filling of the electron shells of the stopping medium atoms. In the case of noble-gas atoms, a correlation is observed between the position of the maximum and the value of the orbital velocities of the electrons in the filled p-shells. The results obtained may be used to help in making an optimal selection among the methods for giving a semiempirical description of the stopping cross sections and to substantially improve the accuracy of such a description.

'Stripping' of the atom in bremsstrahlung

In this letter the 'stripping' of atomic electron shells in the process of fast-electron bremsstrahlung (BS) is considered.

On the mechanism of formation of ion-excited KLnX-ray satellites of the third period atoms of molecules

On the basis of data in the literature and calculations carried out by the present authors of the KLn X-ray transitions in Si, S and Cl atoms of heavy ion-excited molecules, the main factors determining the formation of such spectra for the third period elements have been clarified. It has been demonstrated that in analysing the experimental values of KLn line energies it is necessary to take into account the effects of atomic and extra-atomic relaxation, multiplet effects and the possible ionisation of the outer electron shells of target atoms. A simple technique of treating X-ray satellites of multiple ionisation has been developed and tested. This technique allows one to determine from experimental spectra the contribution of extra-atomic relaxation effects to the chemical shifts of KLn lines. These data can be used for analysing the tendencies of changes in the electron polarisability of the substance.

Shake-up processes accompanying electron transitions in atoms

Elementary processes in many-electron atoms—radiative and Auger transitions, photoionization, ionization by electron impact, etc.—are usually accompanied by relaxation of the electron shells. The conditions under which such an inherently many-electron problem can be solved in the shake-up approximation are examined, and the shake-up processes occurring as a result of electron transitions are described from a unified point of view. The features that are common both to this form of excitation and to the shake-up of atomic electrons following nuclear transformations are pointed out, and the distinguishing features are also noted. The various electron shake-up processes considered are the radiative Auger effect, the two-electron-one-photon transition, double ionization, spectral line broadening, the post-collision interaction, Auger decay stimulated by collision with a fast electron, and three-electron Auger transitions (the double and half Auger effects). These processes are classified according to the type of electron transition causing the shake-up, and the experimental data and methods of theoretical description are reviewed. Other effects of a similar nature that could accompany transitions in the electron shells of atoms are also mentioned. A derivation of the shake-up approximation is given, and it is pointed out that this approximation is to a large extent analogous to the distorted-waves approximation in scattering theory. It is shown that the shake-up approximation is rather effective for obtaining estimates of the probabilities of the various effects.

RADIATION-INDUCED DEFECTS FORMATION IN CHALCOGENIDE GLASSES

ilign-energy (2;,ev) electron irradiation may produce excess density of valence-alternation pairs (VAY1s) in chalco- genide glasses. Relativistic electron energy losses and non- equilibrium density of radiation-induced shiftudefects in vitreous As S and As2Seg are calculated. Zadiation-induced defects formatgo2 scheme is proposed and compared with posit- ron annihilation data. It is shown that radiation-induced de- fects may cause essential changes in electrical and optical properties of chalcogenide glasses. Zelativistic electron (C. 5 < E < lO?.Tev) irradiation lead to ef - fective structural changes in chalcogenide glasses, becouse high- energy electrons are capable to cause both atomic electron shells ionisation and shiftu defects formation. As calculation show practically each atom is ionised during 2 :Lev electron irra diation in vitreous As S and As2Se3. Znergy losses in these materi- 2 3 als amount to -dE/dx= 0.35.,~ev/nlrn and 0. 49A;-ev/m,respectively. Obvio- usly, deep shell electrons ionisation may not cause irradiated glass matrix structural cha~des. tiowever,high-energy electrons ionise only atonric valeme electrons to the conduction band after energy losses in some caskade -1rocesses. In this case chemical bonds are broken, binding peculiarities are affected and new structural defects are formed. Ve suppose that ioiiising effect of electron irradiation re- sults in excess density of the existing charge defects C; and C; ac- cording to the scheme:

Mössbauer Study of the 3d5 Shell Deformation of Fe3+ Ions in MnFe2O4

AbstractThe deformation of the 3d5 electron shell of iron atoms in an MnFe2O4 spinel is investigated by means of Mössbauer effect measurements with 60 kOe and without an external magnetic field at 4.2 K. An analysis of ME spectra is carried out using neutron spectroscopy data. It is found that the 3d5 shell deformation observed by neutron spectroscopy brings about the quadrupole splitting 23d = −0.040 mm/s. A change of the charge density at 3d5 electron shell is calculated to be about 0.3%. A dipole magnetic contribution to the effective field on iron ions in octahedral sites, HD, is estimated as +17.6 kOe. The magnitude of all other hyperfine interaction parameters of 57Fe nuclei are also given.

The influence of atomic electron shell structure on the characteristics of two-electron-one-photon transitions

The probabilities for two-electron-one-photon transitions to K and L shells with two vacancies have been calculated in the present paper on the basis of many-body perturbation theory for atoms and ions for a wide range of variation of the atomic number Z. All possible dipole correlated transitions of L and M electrons are considered and the influence of the number of L and M vacancies on their characteristics is investigated. The branching ratios of the one- and two-electron transitions: 1s-1-2p-1 and 1s-2-2s-12p-1, 2s-1-3p-1 and 2s-2-3s-13p-1 as well as 2p-1-3s-1 and 2p-2-3s-13p-1 have been calculated. The results obtained show that the branching ratio of one- and two-electron transitions of M electrons to the L shell with two 2s vacancies is strongly dependent on the population of the M1 subshell. And in the case of the 2p-2-3s-23p-1 transition the value of the ratio changes considerably with the number of vacancies not only in the M2,3 but also in the L2,3 subshells. The result is a strong sensitivity of the Z dependence of the characteristics of two-electron-one-photon transitions observed in ion-atom collisions to changes in the structure of the electron shells of colliding atomic systems.

Theoretical justification of Madelung's rule

Provides theoretical and physical meaning to the sequence of filling electron shells of neutral atoms in the periodic table dictated by Madelung's rule.

Collision-induced I(52P1/2–52P3/2) radiative transition

An investigation was made of the dependences of the initial I(52P1/2)→I(52P3/2)+hν (λ = 1315nm) luminescence signal on the pressure and nature of the buffer gases. Atoms of I in the 52P1/2 state were formed, in initial concentrations of (0.5–3)×1016cm−3, as a result of photolysis of CF3I (0.01 atm) by the fourth harmonic of a Q-switched neodymium laser (E~0.6 J,τ ~2×10−3 sec). The I(52P1/2) luminescence was recorded by a germanium photodiode whose time constant was (3–4)×10−7 sec. When CF3I was diluted with Ar, Xe, and SF6 buffer gases, the intensity of the luminescence of the I(52P1/2) atoms increased because of an increase in the probability of the 52P1/2→52P3/2 transition as a result of collisions of the iodine atoms with the atoms or molecules of the buffer gases. The dependence of the probability of the investigated transition on the nature and pressure of the buffer gases was determined in the pressure range ~0–1 atm. Estimates were obtained of the oscillator strengths corresponding to the matrix elements of the induced electric dipole moment due to the deformation of the electron shells of the iodine atoms in collisions.

The interplay of nuclear and chemical physics

A review is given of the interplay of ideas and methods used in the study of the structure of matter at the four main conceptual levels of chemistry and physics, i.e., elementary particles, nuclei, atoms, and molecules. Examples are quoted of achievements in the study of radioactivity, including the formation and properties of the heaviest elements and new atoms in which the proton or electron is replaced by a different elementary particle. Emphasis is placed on the importance of hyperfine interactions between the nucleus and the atomic shell electrons, and between inner and valence shells, which form the basis of most modern experimental methods in chemical physics. The possible interrelation between dissymetry in the bioorganic world and the nonconservation of parity in weak interactions is discussed in the light of experimental work in this field. This suggests that one of the main problems in chemical and biochemical physics is the acquisition of dynamic structural data on the properties of molecules, i.e., the establishment of a connection between changes in the electron structure of molecules and their functional motion.

On the problem of the existence of collective oscillations in atoms

The existence of collective oscillations in the electron shells of atoms is discussed. By solving numerically the equations for the effective interaction in the random phase approximation with exchange, it is shown that, at least for atoms of the noble gases, there are no collective levels in the excitation spectrum. Nevertheless, the many-electron correlations play an important role, so that there is a significant difference between the effective and the Coulomb interaction.

How We Prepare Eighth-and Ninth-Graders for the Study of Organic Chemistry

Now that an entirely new syllabus is being used for the high-school course in inorganic chemistry, pupils are proving to be theoretically better prepared for embarking on the study of organic chemistry, above all because of their more thorough knowledge of the periodic law and the periodic system of elements, learned on the basis of the electron theory. They have a clear conception of atomic structure and of how this structure affects the properties of elements. They are able to see the chemical bond as the product of a specific interaction between the electron shells of atoms, and they understand valence. Finally, they are able to explain the properties of matter in terms of charge size, atomic and ionic radii, the type of chemical bond, and the type of crystal lattice.