451 research outputs found
A classical two-body Hamiltonian model and its mean field approximation
We extend a recent billiard model of the nuclear N-body Hamiltonian to
consider a finite two-body interaction. This permits a treatment of the
Hamiltonian by a mean field theory, and also allows the possibility to model
reactions between nuclei. The density and the mean field potential can be
accurately described by a scaling function which shows the qualitative features
of the liquid drop picture of the nucleus.Comment: 9 pages, 2 PS-figures, uses psfig.st
The rotating, charged or gravitating liquid drop, and problems in nuclear physics and astronomy
Ambiguities in statistical calculations of nuclear fragmentation
The concept of freeze out volume used in many statistical approaches for
disassembly of hot nuclei leads to ambiguities. The fragmentation pattern and
the momentum distribution (temperature) of the emanated fragments are
determined by the phase space at the freeze-out volume where the interaction
among the fragments is supposedly frozen out. However, to get coherence with
the experimental momentum distribution of the charged particles, one introduces
Coulomb acceleration beyond this freeze-out. To be consistent, we investigate
the effect of the attractive nuclear force beyond this volume and find that the
possible recombination of the fragments alters the physical observables
significantly casting doubt on the consistency of the statistical model.Comment: 11 pages+3 figure
Nuclear Ground-State Masses and Deformations
We tabulate the atomic mass excesses and nuclear ground-state deformations of
8979 nuclei ranging from O to . The calculations are based on the
finite-range droplet macroscopic model and the folded-Yukawa single-particle
microscopic model. Relative to our 1981 mass table the current results are
obtained with an improved macroscopic model, an improved pairing model with a
new form for the effective-interaction pairing gap, and minimization of the
ground-state energy with respect to additional shape degrees of freedom. The
values of only 9 constants are determined directly from a least-squares
adjustment to the ground-state masses of 1654 nuclei ranging from O to
106 and to 28 fission-barrier heights. The error of the mass model is
0.669~MeV for the entire region of nuclei considered, but is only 0.448~MeV for
the region above .Comment: 50 pages plus 20 PostScript figures and 160-page table obtainable by
anonymous ftp from t2.lanl.gov in directory masses, LA-UR-93-308
Fusion hindrance and roles of shell effects in superheavy mass region
We present the first attempt of systematically investigating the effects of
shell correction energy for a dynamical process, which includes fusion,
fusion-fission and quasi-fission processes. In the superheavy mass region, for
the fusion process, shell correction energy plays a very important role and
enhances the fusion probability when the colliding partner has a strong shell
structure. By analyzing the trajectory in three-dimensional coordinate space
with the Langevin equation, we reveal the mechanism of the enhancement of the
fusion probability caused by `cold fusion valleys'. The temperature dependence
of shell correction energy is considered.Comment: 31 pages, 23 figures, Accepted for publication in Nuclear Physics
True ternary fission of superheavy nuclei
We found that a true ternary fission with formation of a heavy third fragment
(a new type of radioactivity) is quite possible for superheavy nuclei due to
the strong shell effects leading to a three-body clusterization with the two
doubly magic tin-like cores. The simplest way to discover this phenomenon in
the decay of excited superheavy nuclei is a detection of two tin-like clusters
with appropriate kinematics in low-energy collisions of medium mass nuclei with
actinide targets. The three-body quasi-fission process could be even more
pronounced for giant nuclear systems formed in collisions of heavy actinide
nuclei. In this case a three-body clusterization might be proved experimentally
by detection of two coincident lead-like fragments in low-energy U+U
collisions.Comment: 4 pages, 7 figure
Is binary sequential decay compatible with the fragmentation of nuclei at high energy?
We use a binary sequential decay model in order to describe the fragmentation
of a nucleus induced by the high energy collisions of protons with Au nuclei.
Overall agreement between measured and calculated physical observables is
obtained. We evaluate and analyse the decay times obtained with two different
parametrisations of the decay rates and discuss the applicability of the model
to high energy fragmentation.Comment: 6 pages, 4 eps figures. Small changes at the end of the text. More
arguments are given in the discussion of the time scale of the proces
Theory of fusion hindrance and synthesis of the superheavy elements
The two-step model for fusion reactions of massive systems is briefly
reviewed.By the use of fusion probabilities obtained by the model and of
survival probabilities obtained by the new statistical code, we predict residue
cross sections for 48Ca+actinide systems leading to superheavy elements with
Z=114, 116 and 118.Comment: 7 pages, 4 figures, Halong Bay meeting proceedin
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