No abstract available

[en] The resonance integral of neutron capture on ²⁴⁴Pu is measured by the cadmium ratio method and comparing with a gold sample. The obtained value 40.0+-3.0 b agrees well with the results of investigations carried out earlier

[en] Results of research on the synthesis and investigation of properties of heavy nuclei in the bottom of the Periodic chart of elements carried out by the FLNR (Dubna) - LLNL (Livermore) collaboration are presented. These results have led to the observation of a new region of nuclear stability near the closed deformed shells Z=108, N=162 predicted by the macro-microscopic theory. The research has been carried out at the FLNR (JINR) with beams from the U=400 heavy ion accelerator using the Dubna gas-filled separator of recoils. The heaviest isotopes Z=104, 106, 108 and 110 have been synthesized in hot fusion reactions of ²³⁸U, ²⁴⁴Pu and ²⁴⁸Cm nuclei with ions of ²²Ne and ³⁴S. Their radioactive properties point to a substantial increase of stability with respect to spontaneous fission in the whole known region of nuclei of transfermium elements with N=158. The vartial half-life for the ²⁶²104 nucleus with respect to spontaneous fission has been experimentally determined: T_sf=1.2_0.5^+1.0 s. All other isotopes with Z≥106 undergo mostly the α-decay. The experimental systematics of the α-decay energies Qa(N) for all the known isotopes with Z=98-110 determines the status and strength of structural effects near closed deformed neutron shells N=152 and N=102. It is demonstrated that the calculated values of nuclei near shells N=162 are in a good agreement with the experiment. The discovery of a new region of nuclei stability near closed deformed shells allows to make more accurate assessments regarding the properties of heavier nuclides up to Z=120 and N=190. For them a much stronger effect from spherical shells Z--l 14 and N=180-184 is predicted, which opens a possibility of further progress into the region of superheavy elements. The prospects of making superheavy nuclei and the advantages of using different types of fusion reactions are discussed

[en] The experiments in both high- and low-energy physics are planned so that physically interesting effects mathematically are rare (or small probability) events, compared to others, whose probabilities are not small. Correspondingly, the purpose of the paper was the development of the formalism for the treatment of rare events, which could be an inevitable alternative to methods requiring too much of a priori information about the studied effect, in a situation when such an information is absent, but, instead, information is available, e.g. from the calibration measurements. The main topics of the paper were: (1) To what extent the methods of Poisson time-event streams are suitable for the goal declared? (2) What information can be extracted from the calibration measurement which registered zero interesting events? The method described is illustrated by the analysis of data registered in the experiment on the synthesis of the element 114

[en] In bombardments of ²⁴⁴Pu with ³⁴S we discovered the α-decaying nuclide ²⁷³110. We conducted an extensive off-line search of the raw data for event sequences which fit the expected pattern of implantation in a position-sensitive detector and subsequent decay of ²⁷³110 and its descendants. We observed one three-member sequence of genetically linked α decays, resulting in E_α=11.35 MeV, a half-life of 0.3_-0.2^+1.3 ms, and a production cross section of about 0.4 pb for ²⁷³110. Other possible ²⁷³110 event chains were also observed. The measured α-particle energy for the N=163 nuclide ²⁷³110 provides direct evidence for a neutron shell closure at N=162. copyright 1996 The American Physical Society

[en] Dmitri Mendeleev in 1869, proposed the periodic table of 63 elements in 1869, based on the premise that the properties of various elements are periodic functions of their atomic masses. Since then the periodic table has undergone drastic changes, not only in terms of the basis of classification of elements, based on their atomic number (1913), but also in terms of the addition of 55 new elements. The major milestones in this journey of evolution of periodic table have been in the decade of 1940s, when the actinide elements were discovered in the world war-II era as well as during the subsequent years till recently with the discovery of so called 'Super Heavy Elements'. In the present a historical account of the journey of periodic table has been given, including the various new concepts (viz., actinide concept) that led to the modern periodic table as well as the latest discoveries of the so called super heavy elements and the future prospects for the extension of the periodic table. (author)

[en] Macro-microscopic theory of nuclear structure predicts a substantial increase in the stability of deformed nuclei near Z = 108 and N = 162. Nuclei near this region can be produced in hot fusion reactions with the neutron-rich targets ²⁴⁴Pu and ²⁴⁸Cm. Cross sections for production and fission rate of actinide and transactinide nuclei in heavy ion reactions were determined experimentally. It has been found that the radioactive properties of two newly discovered isotopes of element 106 confirm directly the theoretical predictions of enhanced stability for the N = 162 subshell. Prospects for synthesizing isotopes of elements with Z > 106 are discussed

[en] Complete text of publication follows. In the bombardment of a ²⁴⁴Pu target with ⁴⁸Ca ions, we observed two identical decay sequences of genetically linked events, each consisting of an implanted heavy atom, two subsequent a-decays, and terminated by a spontaneous fission. The measured a-energies and corresponding half-lives of the sequential chain members were: E_a = 9.84 MeV (T_1/2 = 1.9 s) and 9.17 MeV (T_1/2 = 9.8 s); for the spontaneous fission (T_1/2 = 7.5 s), the total energies deposited in the detector array were 213 and 221 MeV. The decay properties of the synthesized nuclei are consistent with the consecutive a-decays originating from the parent even-even nucleus ²⁸⁸114, produced in the 4n-evaporation channel with a cross section of about 1 pb. ²⁸⁸114 and ²⁸⁴112 are the heaviest known a-decaying even-even nuclides, following the production of ²⁶⁰Sg and ²⁶⁶Sg (Z = 106) and the observation of one a-decay of ²⁶⁴Hs (Z = 108). The observed radioactive properties of ²⁸⁸114 and the daughter nuclides match the decay scenario predicted by the macroscopic-microscopic theory. (author)

[en] The hunt for searching the limits of mass and charge in nuclear landscape has been a topical issues among nuclear physics community from the last twenty years during which a remarkable experimental progress in the study of structural and decay properties of superheavy nuclides has been achieved. Currently, the shortest life time that still enables the identification of evaporation residue (ER) is about 10 microseconds. The current frontier in superheavy nuclides is at Z=118 but the possibility of still heavier superheavies to form an island of stability on the nuclear chart is conceivable. Thus until now SHN with Z less or equal to 118 have been synthesized in the laboratory with no evidence on the production of nuclei with Z > 118 obtained so far, except for an attempt to produce Z = 120 superheavy nuclei through the "2"4"4Pu + "5"8Fe reaction

No abstract available