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  • 1985-1989  (4)
  • 25.70.Jj  (3)
  • 25.85.Ca  (2)
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  • 1
    ISSN: 1434-601X
    Keywords: 23.60.+e ; 25.70.3f ; 25.85.Ca ; 27.9.+6
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We identified twoα-emitting isotopes of element 107 with masses of 261 and 262 respectively by parent-daughter correlations. For the isotope with mass 262 we found two transitions with (102±26) ms and (8.0±2.1) ms half-life, which we assign to the groundstate and to an isomeric transition, respectively. The half-life of the isotope with mass 261 is (11.8 −2.8 +5.3 ) ms. Spontaneous fission, which could be assigned to the decay of an isotope of element 107, was not detected in our experiments. This observation is in-line with our previous results, indicating a region of nuclei with strong microscopic stabilisation in the trans-actinides. Both new isotopes were produced by complete fusion of209Bi with54Cr. The production cross sections are (163±34) pb for262107 and (36 −14 +22 ) pb for261107.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-601X
    Keywords: 23.60.+ e ; 25.85.Ca ; 25.70.Jj
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In irradiations of207Pb and208Pb, respectively, with54Cr theα-decay of the isotopes259106,260106, and261106 could be observed for the first time. For260106 a spontaneous fission branch of (50 −20 +30 )% was observed. The isotopes were identified by genetic relationships of α-decay after separation in-flight with the velocity filter SHIP and implantation into a position-sensitive silicon surface-barrier detector. The measured partial fission halflife of the doubly even isotope260106 of (7.2 −2.7 +4.8 )ms exceeds the predicted values by at least a factor of 40. This result could be explained by the high shell corrections of the ground state mass, derived from the measured α-decay energies. The experimental results show evidence for an island of purely shell stabilized nuclei in the region of deformed isotopes beyond the actinides.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1434-601X
    Keywords: 23.60.+ e ; 25.70.Jj ; 27.9.+b
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The experiment having led to the discovery of first isotopes of element 108, as published previously in Short Notes to this Journal [1, 2] are described and discussed in a final paper. Two isotopes of element 108 were produced by complete fusion of207Pb and208Pb, respectively, with58Fe. Both isotopes areα-emitters. For the isotope with mass 265 threeα-decay sequences were observed. Theα-decay energy is (10.36±0.03) MeV, the half-life (1.8 −0.7 +2.2 ) ms. For the isotope with mass 264, which is the heaviest doubly even isotope known at present, the decay sequence of one atom was found. The measured half-life is (76 −36 +364 ) μs. Our experimental results point towards an enhanced stability of the heaviest elements against spontaneous fission, which was already observed for element 106.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 327 (1987), S. 217-224 
    ISSN: 1434-601X
    Keywords: 25.70.Jj
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The height and position of the fusion barrier for the real part of the interaction potential between two colliding nuclei are studied as a function of the Coulomb strength. The calculations are performed in the framework of the spherical constrained HF + BCS formalism using the frozen approximation. The effective Skyrme type force SKa is used. The model contains no free parameters. For the height of the fusion barrier good agreement is found with the values obtained using the empirical Bass potential that is known to reproduce well the data for many nuclear systems. In contrast, the recently observed apparent rise of the fusion barrier (‘extra-extra-push’) for very massive nuclear systems with a product of nuclear chargesZ 1 xZ 2 above 1600 cannot be reproduced. We also give estimations for the overlap of the mass densities of both colliding nuclei at the fusion barrier distance.
    Type of Medium: Electronic Resource
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