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This is a theoretical study of argon plasma under conditions, where Ne- and Na-like ionization stages are dominant. Balance equations are generalized to treat 37 3l states of Ne-like ion and 37 adjacent series of Rydberg states of Na-like ion simultaneously. This allows us to include in the kinetics a diffusion-like motion of the state of the system Ne-like ion plus one electron through the multitude of excited levels spread over an energy region of 50 eV. The populations Ni - i (i = (1, ..., 37)) of the Ne-like ion states are introduced explicitly; those of adjacent 37 Rydberg series are accounted for through continuous functions Ni(e). These functions describe the population distribution within each Rydberg series dependent on the Rydberg electron enegy e. The elementary processes of the collisionalradiative model connecting all Ne- and Na-like states, as well as processes of redistribution of populations inside each Rydberg series, are accounted for. The rate coefficients for all processes within the Ne-like residue have been calculated previously, using a detailed many-body relativistic theory. The dielectric capture cross sections and autoionization probabilities are presented as analytical continuation of the collisional excitation cross sections. The excited-excited states transitions are included. The rest of the processes are treated in a simple semiclassical approximation. The Lotz formula is generalized by unambiguous analytical continuation to cover the case of bound-bound transitions between Rydberg states of Na-like ions. The radiation reabsorption in a long plasma cylinder is included through Biberman-Holstein coefficients for all transitions. The inclusion of Na-like states, accounting for diffusion-like processes, increases the population inversion for the lasing candidates by at least a factor of two for a wide range of plasma conditions. This is important for the ionization equilibrium too. Besides, the functions Ni(e) bear diagnostic information. Detailed calculations have been done for the homogeneous steady-state Maxwellian plasma. The role of transient processes in the population inversion creation is under discussion.

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.

Numerical calculations of the inner-shells atomic ionization probabilities and of the electron?positron pair production probabilities (in the bare nucleus) are carried out. The spectra of the ejected electrons as well as the spectra of the produced positrons have fine quasi-periodical structures (~ 3000 eV) scaled by the inverse length of the De-Brogle wave of the ?-particle. Another, large scale type, structurization is governed by the inverse length of the De-Brogle wave of the free electron or positron. The structure of the emitted light particles spectra is shown to be very sensitive to the model of the nucleus decay.

The energies and the widths of the Stark resonances for the hydrogen atom are calculated using a new approach. It is based on the operator form of the perturbation theory of the Schrodinger equation. The method includes the physically reasonable distorted-waves approximation in the frame of the formally exact quantum-mechanical procedure. The zero-order Hamiltonian possessing only stationary states is determined only by its spectrum without specifying its explicit form. The method of calculation of the perturbation theory matrix elements is described.

The values of energies and autoionization widths of 4f13 j6s(J12)ns, np (J) Tm states are presented. These values are calculated by the relativistic perturbation theory with zero-order model approximation. The contribution of effects of the first non-vanishing order (first perturbation theory order for the energies and second order for the autoionization widths) is formally calculated exactly. The effects of higher perturbation theory orders are effectively accounted for. The states superposition is reduced to diagonalization of the secular energy matrix of the states with the same j, n, l and J. Two types of autoionization decay are possible for the states investigated: Beutler-Fano decay and reorientation decay. The reorientation decay has been proved to be the main decay channel when it is due to the monopole interaction of the ejecting Rydberg electron with the atomic residue. Some possibilities of observation of the states studied and measurement of their autoionization widths are proposed.

The numerical calculation of the electron-positron pair production cross-section is carried out. The positron energy spectrum has narrow peaks and dips related to resonance states of the compound superheavy nucleus. The contribution of the spontaneous channel to these irregularities proved to be insignificant in our model. The process takes place mainly at the internuclear separations about 40 fm. The more complicated system with residual atomic shells can be treated in the same way. It is shown that the positron and electron spectra appearing in this system must be modulated by the NS'-resonances.

The electron-positron pair production in collisions between two heavy nuclei with near-threshold energy is considered. A consistent quantum-mechanical approach to the electron-nuclear system as a whole is developed, account being taken of the relativistic nature of the electron subsystem. The motion of the electron and nuclear subsystems is regarded as being independent in the zero-order approximation. The high-order corrections coupling of the two subsystems are accounted for effectively. The model potential of the whole system accounts for the finite size of nuclei and possible resonances of the superheavy compound nucleus formed from the original nuclei. The zero-order potential of the electron subsystem satisfies the following conditions: (1) its spectrum qualitatively coincides with the spectrum of the potential of the electric field of the compound nucleus including the diving of the bound atomic state into the negative continuum at super-critical total nuclear subsystem charge Z, (2) the "no-particle" state of the system is stationary relative to the spontaneous pair production in the zero-order approximation, (3) the perturbation is small at any internuclear separation and vanishes at asymptotically large separations. Resonance phenomena in the nuclear subsystem lead to the structurization of the positron spectrum produced. The fine structurization reflecting details of the compound nucleus spectrum is the characteristic feature of the system with a rather shallow potential pocket (< 1 MeV). The article deals with this effect.

The rates of autoionisation decay of the 4fj13,6s12/(J12)npj (J) Tm states have been calculated. Two qualitatively different channels of autoionisation decay have been considered: 4f52/136s12/npj to 4f72/136s 12/+ in l (Beutler-Fano decay) and 4fj13, 6s(J12)npj to 4fj13,6s12/(J'12)+ in l (reorientation decay). The first process is accomplished with an energy transfer to the Rydberg electron of delta E approximately 8500 cm-1. This channel is opened at n>or=7. The second low-energy decay ( delta E approximately 250 cm-1) is opened at n>or=25. The reorientation decay proceeds without change of the atomic residue electron configuration. The change of the relative rates of radiation and autoionisation decay along the Rydberg series has been investigated. It has been shown that for the system under consideration the radiation decay is at least one order of magnitude lower than the autoionisation one. In most of the cases considered the reorientation autoionisation is the main decay channel, when it is opened.

For pt.I see ibid., vol.10, p.1001 (1977). A formally exact perturbation expansion with a model zeroth-order approximation has been applied to the semi-relativistic equation for a many-electron system. The energy levels of Mo and Zr ions with two electrons or two vacancies above the 1s22s22p63s23p63d10 core have been calculated. It is shown that the experimental spectra for systems with two quasi-particles above the core may be used to investigate more complex spectra, with three or more quasi-particles.

Asymptotically precise calculations have been carried out with n to infinity , for the Rydberg states 4f136sns of the Tm atom, the 4f146sns, 4f146snp states of the Yb atom and the Lu+ ion, the 4f14ns, 4f14np, 4f14nd states of the Yb+ and Lu2+ ions and the 4f146s2ns, 4f146s2np, 4f146s2nd states of the Lu atom. The Lu atom and Yb+ and Lu2+ ions are considered as a system with one electron above the core of the closed shells 4f146s2 or 4f14. The Yb atom and Lu+ ion are regarded as a system with two electrons above the core. The Tm atom is considered as a system with 4f-1 vacancy and the 6s, ns electrons above the 4f14 core. In calculating energies with one electron above the core the energy is extrapolated as a function of the principal quantum number n by the model potential technique. The potential constructed at this stage is used as a zero-order approximation in calculating states with two and three quasiparticles (vacancies and electrons) above the core. The corrections for the energies of the states of two- and three-quasiparticle systems are calculated with the use of the perturbation theory. The first order has been allowed for completely. In the higher orders effective allowances have been made for the corrections which with n to infinity make contributions of approximately 1/n3. Consideration is given to the non-Coulomb features of Rydberg spectra not vanishing within n to infinity .

A theoretical analysis is made of the method of selective ionization of atoms based on selective resonance excitation by laser radiation to quantum states near the ionization threshold and subsequent autoionization decay of the excited states under the influence of an external electric field. The autoionization of atoms in static and pulsed electric fields is considered. Calculation formulas are obtained for the probability of autoionization of a hydrogenlike atom and corrections are computed for the influence of the electron shells. Numerical estimates are obtained for the autoionization of the n = 7–12 states of the Rb atom in an electric field.

The transition probabilities and radiation widths of the 4f136snRlR(nR=10-50, lR=0; 1) Rydberg states of the Tm atom have been calculated in the electric dipole approximation. Special attention has been paid to the manifestation of non-Coulombic properties of the Rydberg states considered. The calculation has been carried out using relativistic perturbation theory with a model zero-order approximation. The formalism of the energy approach to the atomic processes theory has been used. The contributions of the one- and two-quasiparticle effects to the complex energy matrix have evidently been taken into account. The three-quasiparticle effects have been effectively accounted for.

A model potential relativistic method is used to calculate the energies of the lower levels with configurations 4s4p, 4p2, 4s4d, 4p4d in the Zn I isoelectronic series for nuclear charges Z=36-50. The calculation is made in the first order of perturbation theory with the effective inclusion of higher corrections. The role of various correlation effects is evaluated: core polarisation due to outer electrons, superposition of configurations, mutual screening of the outer electrons. As a zeroth approximation the authors obtain the wavefunctions of the outer electron in the field of the core model potential; the model potential parameter being determined from the empirical energy levels of Cu-like ions. An extrapolation procedure for model potential parameters is used for the calculation of energy levels of Cu-like ions. Energy levels 4lj and 5lj of Cu-like ions for Z=36-60 are given with an accuracy of about 0.1%. The accuracy of the energies of Zn-like ions is within 1%.

A formally exact perturbation theory with a model potential is developed as a zeroth approximation for atomic systems. A potential of zeroth approximation for a complex system with an arbitrary number of electrons in an open shell and an arbitrary number of vacancies in the core is constructed semiempirically using experimental data for the simplest spectra of one-electron states in an open shell. A field form of perturbation theory is used to calculate energy corrections. Diagrams of the first two orders are considered and an effective summation is performed of diagrams describing major interactions in the system. Energies of all positive Fe ions with open shells n=3 and 4 and one vacancy (1s, 2s, 2p or 3p) are calculated.

The relativistic perturbation theory is applied to the solution of the many-electron Dirac equation. The theoretical consideration is accomplished for some Mg-like ions: S V, Ca IX, Ti XI and Fe XV; the energies of all the states 1s2 2s2 2p6 3l1j1, 3l2j2 are calculated. The Ne-like spectra are calculated for the ions with Z = 16-26; all the states of configurations 1s2 2s2 2p5 3s, 3p, 3d and 1s2 2s2p6 3s, 3p, 3d are considered. The Dirac equation with the central one-particle model potential Vc(r) is accepted as a zeroth approximation; the model potential imitates the core potential of the closed shells. The empirical information about the energy structures of one electron above the core or one vacancy inside the core is used here to construct the zeroth approximation. The perturbation theory first order correction is calculated exactly, the high order contributions are accounted for effectively. Two main types of high order corrections are investigated: "polarization" interaction of two "above core" particles and effect of the mutual screening of these particles.

The first calculation of the ground state of the two-dimensional excitonic molecule has been performed. The authors have used the transformation of the coordinates of four bodies with equal masses which excludes the motion of the centre of mass, and allows the isolation of one weakly interacting quasiparticle and a core of two strongly interacting quasiparticles in an effective three-body problem. Since the core problem is exactly solved and the form of the variational wavefunction of the system takes into account the essential part of the exchange interactions, satisfactory values are obtained for the binding energy of the two- and three-dimensional biexcitons even when using rather simple trial functions. The binding energy is E2=0.12 au for a two-dimensional biexciton and E3=0.013 au for a three-dimensional biexciton.

The Kalpha and Kbeta radiation from Fe, Ni and Ti plasmas in a low inductive spark has been investigated both experimentally and theoretically. A high-dispersion and high-resolution Johann crystal spectrograph has been used for the measurements. The theoretical analysis is based on relativistic perturbation theory with a zero-order model approximation. Some Kalpha and Kbeta spectra features are qualitatively explained and some Kbeta lines are identified for the first time. It has been shown that the observed time and space integrated spectrum is due mainly to the low M-shell ions. The calculation shows that this qualitatively explains the long-wavelength Kalpha plasma radiation shift relative to the solid state Kalpha line. The Kalpha radiation from high ions would be shifted to the opposite side.

Wavelengths of 4-5 and 4-4 transitions have been measured experimentally for the Cu-like ions Ag XIX-Sn XXII (Z = 47-50). The Relativistic Model Potential Method has been used for extrapolation and interpolation of the 4lj and 5lj energy levels in the range Z = 36-80. Two versions of calculations were made. In the first one the experimenal energies for Z = 36, 42, 56, 62 were used as references; these results are in good agreement with the new experimental data are used to obtain more accurate calculated values for large Z.

The highly excited 4f72/136s12/(J')npj(J) Tm states lying near the first two ionisation limits of the atom were investigated. The automatic laser setup used contained three dye lasers pumped by a nitrogen one. The states' energies were measured with an accuracy of +or-0.1 cm-1. Two excitation schemes were realised. In the first one, the states with J'=3 were excited; the states of this type with n>or approximately=28 are autoionisation states. In the second excitation scheme, the bound Rydberg states with J'=4 were excited. Identification of the observed levels was performed using the calculation of the spectrum made using relativistic perturbation theory with zero-order model approximation. Unambiguous classification was obtained for the following three series: 4f72/136s12/(3)np32/(9/2) (n=26-65), 4f72/136s12/(4)np32/(11/2) (n=29-57) and 4f72/136s12/(4)np12/(7/2) (n=28-36). For n>27, three shorter series were observed too, for which alternative classifications are possible at the present stage. The experimental results are in very good agreement with the theoretical results, particularly for large values of the principal quantum number n. A peculiar grouping of the states belonging to the different series was observed varying with the variation of n. This confirms the non-Coulombic properties of the highly excited spectrum of the atom considered.

A comparative analysis is made of the parameters of electrooptic light modulators utilizing the Pockels and Franz?Keldysh effects, and designed for the use in integrated optics systems made of gallium arsenide. It is shown that the use of a Franz?Keldysh modulator in integrated optics systems makes it possible to reduce considerably (by more than one order of magnitude) the modulator dimensions and, consequently, reduce the control power and increase the pass band of the modulation frequency. The results are given of an experimental investigation of a macroscopic analog of a film Franz?Keldysh modulator fabricated from high-resistivity gallium arsenide. It is shown that the depth of modulation can reach 60?90% in control fields up to 5?104 V/cm applied to a modulator 150 ? long.