Faculty of Physics
M.V.Lomonosov Moscow State University
Physics of nuclei and elementary particles

## Nucleon pairing in atomic nuclei

### B.S. Ishkhanov$^{1,2}$, M.E. Stepanov$^{1,2}$, T.Yu. Tretyakova$^2$

Moscow University Physics Bulletin 2014. 69. N 1. P. 1

The nucleon pairing effect that is analyzed in the present paper is one of the striking manifestations of nuclear dynamics. Nucleon pairing for different chains of nuclei dependent upon the number of protons or neutrons in the nucleus allows one to explain the emergence of a great number of positive-parity states, which form a ground state multiplet, in even-even nuclei in the excitation energy range E* < 4 MeV. The interaction of paired nucleons with vibrational and rotational degrees of freedom of a nucleus produces a wide variety of excitation spectra of positive-parity states in even-even nuclei.

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Theoretical and mathematical physics

## Formation of the distribution function of the aerosol-particle radii for the hydrolysis products of uranium hexafluoride in industrial premises

### S.P. Babenko$^1$, A.V. Badin$^2$

Moscow University Physics Bulletin 2014. 69. N 1. P. 21

We consider $\mathrm{UO_{2}F_{2}}$, and $\mathrm{HF}$ aerosol particles that formed in the air of industrial premises at a factory of the nuclear industry. The distribution function $g_{1}$ of the aerosol-particle radii at a given space-time point is analyzed. Some of the lognormal distribution functions that are related to a gas-dispersed environment of the working premise are considered. The deviation of $g_{1}$ from lognormal distribution functions is estimated. The related problems of calculating the average transmission coefficients of atoms of toxic substances (uranium or fluorine) in the human body during inhalation are discussed.

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## Monte Carlo modeling of metallic hydrogen: the phase transition and the equation of state

### A.A. Novoselov$^1$, O.V. Pavlovsky$^2$, M. V. Ulybyshev$^2$

Moscow University Physics Bulletin 2014. 69. N 1. P. 29

We conducted numerical modeling of atomic (metallic) hydrogen using the PIMC (path integral Monte Carlo) method. The temperature and density range in which the electron (proton) behavior is governed by quantum (classical) statistics was studied. The equations of state in the form of dependences of the internal energy and pressure on temperature and density were obtained in that region. These dependences allow one to reveal and study the phase transition between crystal and liquid phases.

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Physics of nuclei and elementary particles

## Photodisintegration of molybdenum isotopes

### B.S. Ishkhanov$^{1,2}$, I.M. Kapitonov$^1$, A.A. Kuznetsov$^2$, V.N. Orlin$^2$, H.D. Yoon$^1$

Moscow University Physics Bulletin 2014. 69. N 1. P. 37

The process of photodisintegration of molybdenum isotopes was studied using the induced activity method. The yields of isotopes produced as a result of photonuclear reactions on a natural mixture of molybdenum isotopes were determined at an electron accelerator energy of 67.7 MeV. A comparison of the experimental results with the theoretical calculation carried out using the combined model of photonucleon reactions shows that the model gives a fair description of the experimental yields of photonucleon reactions on all molybdenum isotopes except for $^{92}$Mo. The high yields of the proton channels of photonuclear reactions on the $^{92}$Mo isotope and low yields of the corresponding neutron channels are interpreted based on the shell structure of molybdenum isotopes.

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## Determination of the numerical value of the gravitational constant in the case of a complicated form of interacting bodies

### V.M. Shakhparonov

Moscow University Physics Bulletin 2014. 69. N 1. P. 47

An example of extending the functionality of methods for calculating the gravitational constant for the spherical shape of interacting bodies is presented. The results that were obtained using an apparatus in which the working body is in the form of quartz box are analyzed. A bad choice of the form and material of the working medium for a torsion balance in a vacuum chamber with non-equilibrium flows led to a systematic measurement error.

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## Turbulence-induced laser-beam distortions in phase space

### T.I. Arsenyan, N.A. Suhareva, A.P. Sukhorukov

Moscow University Physics Bulletin 2014. 69. N 1. P. 55

A consecutive analysis of spatial-temporal disturbances of a laser beam propagating through a turbulent media was carried out. Evolutionary equations for the intensity distributions were obtained for a channel with different types of regular and stochastic spatial dispersion. The relative simplicity and physical validity of the integral relationships allows one to build them in the control algorithm for jam-protection of open-space operating channels.

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## Charging potential of dielectrics and insulated conductors as a function of the angle of incidence of an electron beam

### E.N. Evstaf’eva$^1$, S.V. Zaitsev$^1$, E.I. Rau$^{1,2}$, A.A. Tatarintsev $^2$

Moscow University Physics Bulletin 2014. 69. N 1. P. 61

The cardinal characteristics of the charging of dielectric and ungrounded metal targets within radiation by medium-energy electrons (0.5–10 keV) have been studied theoretically and experimentally as a function of the angle of incidence of the electron beam. The coefficients of electron emissions and the second critical energy of primary (radiating) electrons, E$_{2C}$, have been determined as a function of the angle of incidence α when the targets are not being charged.

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Optics and spectroscopy. Laser physics

## Investigation of the temperature dependence for the spectra of supercooled water in the middle infrared

### A.V. Khakhalin$^{1,2}$, A.V. Koroleva$^1$

Moscow University Physics Bulletin 2014. 69. N 1. P. 66

The temperature dependence of the bending ν$_2$, combination ν$_2$ +ν$_L$, and stretching (ν$_1$, ν$_3$, 2ν$_2$) absorption bands in the infrared spectra of supercooled water with a temperature-change step Δt from 2 to 2.5$^0$C was studied using an advanced infrared Fourier spectrometer. It was found that the frequency of the maximum of the stretching absorption band (2700–3700 cm$^{-1}$) decreases with the reduction of the water temperature from -0.5 to -5.0$^0$C. The frequency of the maximum of the combination absorption band (2130 cm$^{-1}$) increases with the reduction of the water temperature in a range from -3.0 to -5.0$^0$C. The frequency of the maximum of the absorption band of bending oscillation (1640 cm$^{-1}$) is invariable with a reduction of the water temperature from -0.5 to -5.0$^0$C.

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Condensed matter physics

## The nonlinear optical properties of nanotubes with spiral defects in a longitudinal magnetic field

### V.Ch. Zhukovskii$^1$, V.D. Krevchik$^2$, M.B. Semenov$^2$, A.V. Razumov$^2$

Moscow University Physics Bulletin 2014. 69. N 1. P. 72

It is demonstrated that the anisotropic transfer of photon momentum to an electronic subsystem results in induction of a photon-drag EMF in a standing electromagnetic wave along the axis of a nanotube with a spiral defect, which confirms the assumption found in the literature that the occurrence of such an effect in the presence of an external magnetic field is possible not only in 2-D systems but also in nanotubes with a spiral symmetry. One of the potential mechanisms of inducing the EMF connected with the spatial asymmetry of the electron-phonon interaction in a nanotube with a spiral defect is considered. This mechanism allows for such an EMF to occur upon heating the electron system by the Joule heat of the photon-drag current that flows through the nanotube.

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## Investigation of the structural state of potassium polytitanate replaced by iron

### M.S. Krivenkov, A.I. Komiak, A.A. Novakova

Moscow University Physics Bulletin 2014. 69. N 1. P. 82

Investigations were carried out for iron ion-substituted potassium polytitanates (PPTs). The mechanism of iron incorporation into the interlayer space of the PPTs, the chemical purity of the polytitanate powders, and the particle morphology were studied. The replacement of potassium ions in the polytitanate structure was experimentally observed and the degree of this substitution was numerically evaluated at different stages of preparation. It was shown that the iron incorporation into the interlayer space of polytitanate was accompanied by the formation of lepidocrocite, which follows from data of Moessbauer spectroscopy. It was found that in the iron ions incorporation process used in the experiment polytitanate particles agglomerate, which may be associated with the formation of lepidocrocite.

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Chemical physics, physical kinetics, and plasma physics

## Radial inhomogenity of plasma parameters in a low-pressure inductive RF discharge

### E.A. Kralkina, P.A. Nekliudova, V.B. Pavlov, K.V. Vavilin, V.P. Tarakanov

Moscow University Physics Bulletin 2014. 69. N 1. P. 86

This work is devoted to systematic investigation into the radial dependence of the plasma parameters of a low-pressure inductive radio-frequency (RF) discharge on pressure within a wide range of 0.8–1 Torr. Experimental results that were obtained under the considered pressures make it possible to analyze the patterns of the changes in plasma parameters upon both a nonlocal mode of discharge and a transition from a nonlocal to local mode of the RF power input. Discharges in helium, neon, argon, and krypton were considered. Experimental data were compared to the results of the numerical simulation of the inductive RF discharge using the particle-in-cell (PIC) method.

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## The impact of the Ramsauer effect on the frequency of elastic collisions in inductive RF discharges in inert gases

### E.A. Kralkina, P.A. Nekliudova, V.B. Pavlov, K.V. Vavilin

Moscow University Physics Bulletin 2014. 69. N 1. P. 92

This paper presents the results of investigating the power absorption mechanism of an inductive RF discharge plasma. Dependences of the frequency of elastic electron collisions with inert gas atoms (helium, neon, argon, and krypton) on the pressure are given. In the frequency range of •10$^6$–3•10$^7$ s$^{-1}$, an equivalent plasma resistance and the power input into the plasma are determined by the values of collision frequency and electron density within a skin layer and do not depend on the type of gas within the limits of experimental error. Upon reaching the electron temperature of -1 eV, the energy of the main part of electrons lies in the range of Ramsauer’s minimum for elastic cross section. This leads to a decreasing elastic-collision frequency in heavy inert gases as compared to helium.

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## Development of nanosecond combined volume discharge with plasma electrodes in an air flow

### N.O. Arkhipov, I.A. Znamenskaya, I.V. Mursenkova, I.Yu. Ostapenko, N.N. Sysoev

Moscow University Physics Bulletin 2014. 69. N 1. P. 96

The space-time characteristics of a nanosecond combined volume discharge with preionization from a plasma sheet with a nanosecond duration in air (∼200 ns) are investigated. The integral discharge radiation, radiation spectrum, and discharge current under conditions within the discharge volume, including gas-dynamic flow with a planar shock wave, are analyzed. It is shown that the volume discharge glow is homogeneous in the master phase. The glow in the area of the shock-wave front increases and its duration may be more than 2 μs.

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