Structure of Giant Nuclear Molecules

Hess, P. O.; Greiner, Walter; Pinkston, W.T.

doi:10.1103/physrevlett.53.1535

Cited by 26 publications

(31 citation statements)

References 9 publications

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“…The influence of higher order terms is discussed. 21.10.Dr; 21.10.Ft Evidence for the "sticking together" of very heavy nuclei in sub-Coulomb collisions has been found two years ago and continues to accumulate [1,2]: the sharp structures in the energy spectra of emitted positrons find a natural explanation [3] in terms of the long life times of 10 -2~ to 10-19S resulting from the sticking. The experiments [1] support the emission of the positrons from the centre-of-mass of the composite system, independent of this theoretical interpretation.…”

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confidence: 98%

The binding energy of 184 476 X in the droplet model

et al. 1985

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The positron spectrum emitted in the U-U-reaction at subthreshold energy could be interpreted in terms of the formation of a giant nucleus if the binding of the latter is 100 MeV stronger than predicted by the usual droplet model parametrisation. We analyse the extrapolation to giant nuclei by accounting properly for the error propagation when the parameters are fitted to measured binding energies and radii. The influence of higher order terms is discussed. 21.10.Dr; 21.10.Ft Evidence for the "sticking together" of very heavy nuclei in sub-Coulomb collisions has been found two years ago and continues to accumulate [1,2]: the sharp structures in the energy spectra of emitted positrons find a natural explanation [3] in terms of the long life times of 10 -2~ to 10-19S resulting from the sticking. The experiments [1] support the emission of the positrons from the centre-of-mass of the composite system, independent of this theoretical interpretation. However, details of the formation of the molecular system are not yet understood. Since the energy of the emitted positrons is related to the energy of the lsl/z-electron state which, in turn, is a function of the two-centre distance R between the molecular constituents, the distance R can be derived from the positron-peak energy. For the system U-Cm, the resulting distance R--~16 fm is in excellent agreement with the prediction of a pocket in the nucleus-nucleus potential [4]. The interpretation of the U-U data, however, demands a value of R _~ 11 fm for the molecular distance which is much smaller than that of the predicted pocket, lying again at 16 fm (in fact, this distance is even smaller than twice the half-density radius of U). In addition, the line structure of the positron spectrum suggests that giant nuclei are possibly formed and that these nuclei are only slightly deformed or are even of spherical form. At present, it is unclear how the Uranium nuclei can come so close together, because the repulsive Coulomb potential cannot be overcome by the beam energy of only 5.7 MeV/u. A possible explanation might be given by the assumption that the binding energy of the ~6X-system be lower than predicted by the conventional droplet model parametrisation: the corresponding lowering of the potential would allow the nuclei to come closer together; this is indicated schematically in Fig. 1. There are several possible reasons for such a reduction in the interaction potential. It could be that the extremely large nuclear charge of the compound system may push the protons much farther out from the centre than one expects from an extrapolation from known nuclei. This possibility has been investigated by J. Fink [5] within a density functional model. Although there is a considerable reduction of proton density near the centre, even leading to bubble nuclei near Z ~400, the net result for the binding energy shows no reduction compared to the standard liquid drop model: the gain in Coulomb energy PACS:

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The binding energy of 184 476 X in the droplet model

et al. 1985

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“…A phenomenological, model for the system of three clusters; with the light fragment in the middle has been proposed by Hess et al [19]. This model was a straight forward extension of reference [20] presented for two clusters. The existence of the collective modes of the tri-nuclear molecular states 96 Sr + 10 Be + 146 Ba, 108 Mo + 10 Be + 134 Te and 112 Ru + 10 Be + 130 Sn with a halflife larger than 10 −12 s have been studied [19][20][21].…”

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confidence: 99%

“…The cold fission of 252 Cf and 262 Rf accompanied by clusters such as α-particles, 10 Be, 14 C, 20 O, etc, were studied by Poenaru et al [12]. They observed minimum barrier height when the fragments are associated with the doubly magic 132 Sn.…”

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Pre-existence probability for the ternary fission of Cf isotopes

Kokila

Balasubramaniam

2020

J. Phys. G: Nucl. Part. Phys.

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The pre-existence probability for the spontaneous ternary breakup of neutron deficient to neutron rich parent nuclei of Cf isotopes from 242Cf to 256Cf with different third fragments such as 4He, and N = Z and N ≠ Z clusters like 12,14C, 16,20O, 20,24Ne, and 48,50Ca is studied here. A simple analytical formula is used to calculate the pre-existence probability. The ternary breakup combinations are computed by the charge minimization procedure. For 4He as the third fragment, the inclusion of deformation shifts the most probable distribution of 252Cf parent system from 132Sn to 140Xe which is as per the experimental observations. An enhancement in the relative yield is observed when the distance between the main fission fragment is reduced. In the spherical calculations for A 3 = 12C and 14C, the yield distribution is identical and the heavy group remains as 132Sn but for the deformed calculations with A 3 = 14C, the light group remains the same as 114Ru for neutron-rich parent nuclei. For O and Ne clusters, with the increase in neutron number of parent system, the asymmetric yield distribution changes to symmetric one. For heavier clusters, 48Ca and 50Ca, the favorable fragmentation is observed as Sn + Ni, which is in agreement with experimental predictions.

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“…In this context also /~-decay processes via K-electron capture could be excluded due to their extremely long decay times [17]. The nuclear physics properties of the giant nuclear systems were studied in various papers [18][19][20]. However, up to now there is no final theoretical explanation of these enigmatical positron structures which explains all observed features.…”

Section: Introductionmentioning

confidence: 99%

Conversion processes in superheavy and giant atoms

Schlüter

Müller

Soff

et al. 1986

Z. Physik A - Atomic Nuclei

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Conversion of bound state electrons and internal e § e--pair creation in superheavy and giant atoms are investigated. We consider various nuclear transitions of multipolarities EO, EL and ML (L> 1) in superheavy atoms with Z> 109. We are concerned in particular with the pecularities of conversion processes in supercritical systems. Our theoretical studies are confronted with the prominent peak structures observed in positron spectra of very heavy collision systems.

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Structure of Giant Nuclear Molecules

Cited by 26 publications

References 9 publications

The binding energy of 184 476 X in the droplet model

The binding energy of 184 476 X in the droplet model

Pre-existence probability for the ternary fission of Cf isotopes

Conversion processes in superheavy and giant atoms

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