CONTENTS

                                                            № 1, 2000

1. STATISTICAL  DESCRIPTION  OF  THE  RADIATIVE  STRENGTH  FUNCTIONS

V. A. Plujko,  S. N. Ezhov,  A. S. Mikulyak

            A closed-form thermodynamic pole approach is developed for average description of the E1 radiative strength functions using the microcanonical ensemble for initial states. A semiclassical description of the collective excitation damping in the method is based on modern physical notion on the relaxation processes in Fermi systems. It is shown that the model is able to cover a relatively wide energy interval, ranging from zeroth gamma-ray energy to values above GDR peak energy. It gives rather accurate means of simultaneous description of the g-decay and photoabsorption strength functions in the medium and heavy nuclei. For gamma-ray energies near neutron binding energies the calculations within the proposed model describe experimental data somewhat better for heavy nuclei with A >150 as compared to other closed-form approaches.

2. DIPOLE  EXCITATIONS  IN  AN  ASYMMETRIC  NUCLEAR  FERMI-GAS

V. I. Abrosimov,  O. I. Davidovskaya

            Dipole excitations of a neutron-proton finite Fermi gas are considered within a semiclassical approach based on the kinetic equation. The independent-particle dipole strength functions connected with the external fields, which are exploited in quantum random phase approximation approaches for studying the isoscalar and isovector resonances in nuclei, are found.

3. Elastic,  inelastic  scattering  and  one-nucleon  transfer  in  the  ¹¹В + ¹²С interaction  at  E_lab(¹²C) = 61 MeV  and  energy  dependence  of  optical potentials

A. T. Rudchik,  S. Y. Mezhevych,  V. A. Ziman,  O. A. Momotyuk,  G. V. Mokhnach,  V. K. Chernievsky, A. P. Ilyin

            The angular distributions for elastic and inelastic scattering of ¹²C ions  on ¹¹B nuclei at E_lab(¹²C) =  1 MeV for transitions to ground and low-exited states of ¹²C and ¹¹B were obtained. These experimental data and data at other energies were analyzed with the help of optical model and model of coupled channel reactions. Energy dependence of the parameters of optical potential for ¹²С + ¹¹В scattering was studied.

4. SOFT  DIPOLE  MODE  OF  NEUTRON-RICH  LIGHT  NUCLEI  IN  ASYMPTOTIC POTENTIAL  APPROXIMATION

G. F. Filippov,  Yu. A. Lashko,  L. P. Shvedov

            Completely antisymmetrized 1^- continuum wave functions as well as the ground state wave function for ⁶He have been constructed in asymptotic potential approximation. The behavior of two-channel S-matrix elements shows on the existence of 1^- resonant state just above the three-body decay threshold of ⁶He.

5. RESPONSE  OF  ELECTRONIC  SURFACE  IN  METAL  CLUSTERS  WITHIN  A  PHASE SPACE  APPROACH

V. I. Abrosimov,  V. M. Kolomietz, V. A. Plujko

            The surface vibrations of the valence electrons in spherical alkali-metal clusters are studied within a phase space approach which is based on the Landau-Vlasov kinetic equation. The linear response theory is used. The proposed method allows for the analysis of the contribution of the electron orbits with different angular momentum into the strength function. The strength function for the electronic surface vibrations is investigated. Applications to the dipole collective excitations in sodium clusters are presented. We reproduce both the surface and volume branches of the dipole resonance. The analysis is carried out for the electron-electron collision integral taking into account the retardation effects. Enhancement of the two-electrons scattering rate in two orders of magnitude due to the memory effects is shown.

6. ELASTIC  SCATTERING  OF  PROTONS  ON  ²⁰Ne NUCLEI  AND  THE  a-CLUSTER  MODEL  WITH  DISPERSION

Yu. A. Berezhnoy, V. P. Mikhailyuk

            The a-cluster model with dispersion is developed to the case of ²⁰Ne nucleus. The differential cross-section and the polarization observables of 800 MeV protons elastic scattering on ²⁰Ne nuclei are calculated on the basis of the a-cluster model with dispersion and the multiple diffraction scattering theory. The results obtained show that a-cluster in ²⁰Ne nucleus takes place incide the deformed core (16О nucleus) with most probability.

7. Investigation  of  the  t + a  system  in  a  Kinematically  complete  experiment  at  energy  Е_a = 27,2 MeV

O. K. Gorpinich,  O. M. Povoroznyk,  Y. S. Roznyuk,  B. G. Struzhko

            The ³H(a,da)n reaction was investigated in a kinematically complete experiment at energy Е_a = 27,2 MeV. Within the framework of model sequential decay the parameters of resonances for the ground and 2Р_1/2 excited states of a nucleus ⁵Не were obtained Е_r = 0,89 MeV, Г = 0,6 MeV and Е_r = 2,0 MeV, Г = 2,0 MeV.

8. IMPROVED  EXPERIMENTAL  LIMIT  ON  THE  ELECTRON  STABILITY  AND  NON-PAULIAN  TRANSITIONS  IN  I  ATOM

P. Belli,  R. Bernabei,  C. J. Dai,  H. L. He,  G. Ignesti,  A. Incicchitti,  H. H. Kuang,  J. M. Ma,  F. Montecchia,  O. A. Ponkratenko,  D. Prosperi,  V. I. Tretyak,  Yu. G. Zdesenko

            The background measurements have been performed in the Gran Sasso National Laboratory of INFN with the help of the large mass (@100 kg) highly radiopure DAMA NaI(Tl) set up. Using statistics of 19511 kg·day, new  limit on the mean life  of the electron was established for "disappearance" channel: t_e(e^- ® n_en_en_e) > 4.2 (2.4)·10²⁴ y at 68 %(90 %) C.L.

9. The  concept  of  the  nuclear  reactor  with  subcritical  core,  neutron  field  control  using  gaseous  or  liquid  flows  of  fissile material

O. V. Nedelin,  V. M. Pavlovych,  S. A. Yatskevych

            The concept of research nuclear reactor with subcritical core of solid fuel which riches the critical state inserting part of the fuel in the form of gas or liquid containing the atoms of fissile material. Such design permits to create the superfast emergency protection and to obtain the satisfactory characteristics of the energy distribution in the core.

10. Determination  of  Functionals  of  Neutron  Flux  Influenced  on  Reactor  Pressure  Vessel  as  a  Statistical  Decision  Problem

V. L. Dyemokhin,  V. N. Bukanov

            Estimating of the neutron flux functionals by a Monte Carlo transport code is shown to be a statistical decision problem. Hence, to choose an estimator, to make a loss function, and to define a joint probability density function are required for the purpose to estimate correctly of the functionals.

11. semiconductor  detectors  for  spectroscopy  of  gamma-radiation

P. G. Litovchenko,  L. I. Barabash,  V. K. Dubovoy,  V. F. Lastovetsky,  T. I. Kibkalo,  N. N. Kolychev,  l. A. Polivtsev,  V. I. Kochkin,  A. P. Litovchenko,  S. P. Batyuta,  V. I. Varnina,  O. I. Fishchuk

            The development of noncooling semiconductor detectors of gamma-radiation on the base of silicon compensated by lithium was carried out. The testing of detectors on sources gamma-radiation ¹³⁷Cs and ⁶⁰Co indicated that their registration efficiency was 2 – 3 %, sensitivity ~ 0,03 imp/s/Bk. Energy resolution of gamma-detectors was 25 - 31 kеV.

12. The  development  of  the  periodical  distribution  of  point  defects  in binary  semiconductors

 V. V. Mykhaylovskyy

             An instability of the stationary uniform distribution of point defects in irradiated binary semiconductors is considered. This instability arises due to elastic interaction of point defects created by radiation. It was shown that the periodical distribution of point defects have to be must developed in some cases. The area of existence and the parameters of this periodical distribution were estimated for GaAs.

13. Modification  of  the  carbon  stripper  foils  nanostructure  with  the  aim  of  radiation  resistance  improvement

А. V. Vasin,  E. N. Mozhzhukhin,  G. N. Kozeratskaya,  A. V.  Rusavsky,  Y. I. Totsky

            The problem of the radiation resistance of the carbon stripper foils is considered. The short historical review and original experimental results of the authors are given. It is considered the correlation of radiation resistance of carbon foils and distribution of the graphitelike nanocrysallites orientations. Raman scattering and atom force microscopy were used for investigation of the carbon films deposited by dc-magnetron sputtering. It is established that the intensity of the ion bombardment during deposition process is a basic technological parameter determining the primary orientation of the graphitelike nanocrystalites.

14. OPTICAL  SOLITONS  IN  MONOMODE  FIBERS

T. A. Davydova,  Yu. A. Zaliznyak

            The evolution of envelope solitons in the framework of generalized nonlinear Schroedinger equation including high-order dispersive effects and of nonlinearity saturation is considered. In terms of Lyapunov method it was shown that model equation have stable soliton solutions in the form of chirped solitons. New exact chirped soliton solution is presented. The dynamics of wave-packets in the vicinity of exact solution was studied using the direct variational approach.

15. the  experimental  observation  of  the  transillumination  of  a  plasma  wave  barrier  by  the  electrons  oscillating  in  it

D. B. Palets,  L. I. Romanyuk

            Previously theoretically predicted effect of transillumination of a plasma barrier for electromagnetic and electron plasma waves with plasma electrons trapped and oscillating within the barrier potential well is observed experimentally.

16. Arising  of  Rayleigh-Taylor  instability  at  the  surface  of  discharge  channel  in  water  and  its  saturation  mechanisms

L. M. Voitenko,  A. V. Kononov,  P. V. Porytsky,  P. D. Starchik

            There were observed perturbations at the channel surface of the pulse discharges in water. The approximate hydrodynamic model of the surface perturbations was developed. It was demonstrated that the perturbations arise due to Rayleigh-Taylor type instability. Mechanisms of instability saturation were considered.

17. Influence  of  low  doses  of  ionizing  radiation  on  the  reproductive  indices  and  physiological  development  of  experimental  animals  in  several  generations

V. M. Indyk,  Ya. I. Serkiz,  A. I. Lipska,  I. P. Drozd,  I. Yu. Nikitina

            It was found out that permanent irradiation in low-level doses at the Chernobyl exclusion zone have unfavourable influence on the reproductive function, postnatal development of some subsequent generations of antenatally irradiated experimental rats and breaked the chromosome structure in bone marrow cells. There are some arguments in witness of this: a decrease of birth rats and the number of newborn rats in bred per rat-mother, an increase in death of babyrats, a reduction of the mass of one-month rats, a retardation of certain physiological markers of development, an increase of the cases of anatomical anomalies. The chromosome aberration frequency in bone marrow cells of Chornobyl-living animals increased.

18. About  chemical  and  biological  stimulation  of  bioleaching  of  ⁹⁰ Sr  from  different  types  of  soil

E. P. Buravlev,  V. V. Trishin,  O. V. Svyatun,  In. S. Kim,  V. N. Ivanov, A. N. Berlizov

            The results of investigation carried out in the frame of international cooperation between the NASU and KOSEF on the creation of effective methods of purification of radioactively polluted soil were performed .The influence of methanogenic, sulfate-reducing, nitrifying and thiobacilli and also their joint activity with different chemical ingredients on bioleaching of ⁹⁰Sr from typical South Korea red soil, artificially radioactively polluted by⁹⁰ Sr, and technogenically polluted by the radionuclides from influenced zone of ChNPP was studied. The presence of the largest effect of thiobacilli on soil was shown.

19. PECULIARITIES  OF  ¹³⁷Cs  BIOGEOCHEMISTRY  IN  ECOSYSTEMS  OF  FOREST  SPHAGNOUS  BOGS:  APPROACH  TO  CREATION  OF  CONCEPTUAL  SCHEME  OF  THE  MODEL

A. A.Orlov,  A. B. Kalish

            The conceptual scheme of the model describing the ¹³⁷Cs cycling in ecosystems of sphagnous bogs was adduced. Compartments of forest-bog ecosystem were united into five main blocks: peat, tree canopy, moss (sphagnous) layer, understorey vegetation, bog water. Radioecological peculiarities of elements of this ecosystem were shown as well as the vertical profile of sphagnous-peat cover. The functional connection among vegetation macroblocks, peat and bog water realises due to special block of mycorrhiza.

20. The  INFLUENCE  of  SOIL  Micromycetes  ON  THE  ACCUMULATION  OF  ¹³⁷Cs  BY  cabbage  and  clover

T. N. Lashko,  A. P. Lashko,  A. I. Vasilevskaya,  N. N. Zhdanova,  T. I. Redchitz

            The results of field experiments for studding of the influence of soil micobiota on the accumulation of ¹³⁷Cs by agricultural plants from the soils of nord (fuel) trace are presented.  Data for two cultures (cabbage and clover) and for two strains of soil micromycetes have been obtained. These data show that in some cases soil micobiota can have dominant influence on the transfer of radionuclides into agricultural plants.

21. OPTIMIZATION  OF  RADIOCHEMICAL  TECHNIQUE  FOR  TRANSURANIUM  ELEMENT  CONTENT  DETERMINATION  IN  ENVIRONMENTAL  SAMPLES

A. N. Berlizov,  V. V. Tryshyn

            Optimization of technique for transuranium element content determination in environmental samples under presence of background component, which is proportional to tracer activity, is considered. Expressions for calculating of tracer solution activity and measuring time optimal values, needed for achieving required precision of the analysis, as well as low limit of detection are obtained. It is shown, that presence of uncertainty in the above background component sets principal limit on the value of minimal activity, which can be measured.