83 research outputs found
Spontaneous heavy cluster emission rates using microscopic potentials
The nuclear cluster radioactivities have been studied theoretically in the
framework of a microscopic superasymmetric fission model (MSAFM). The nuclear
interaction potentials required for binary cold fission processes are
calculated by folding in the density distribution functions of the two
fragments with a realistic effective interaction. The microscopic nuclear
potential thus obtained has been used to calculate the action integral within
the WKB approximation. The calculated half lives of the present MSAFM
calculations are found to be in good agreement over a wide range of observed
experimental data.Comment: 4 pages, 4 figure
Role of effective interaction in nuclear disintegration processes
A simple superasymmetric fission model using microscopically calculated
nuclear potentials has shown itself to be outstandingly successful in
describing highly asymmetric spontaneous disintegration of nuclei into two
composite nuclear fragments. The nuclear interaction potentials required to
describe these nuclear decay processes have been calculated by double folding
the density distribution functions of the two fragments with a realistic
effective interaction. The microscopic nucleus-nucleus potential thus obtained,
along with the Coulomb interaction potential and the minimum centrifugal
barrier required for the spin-parity conservation, has been used successfully
for the lifetime calculations of these nuclear disintegration processes.Comment: 7 page
Complex fission phenomena
Complex fission phenomena are studied in a unified way. Very general
reflection asymmetrical equilibrium (saddle point) nuclear shapes are obtained
by solving an integro-differential equation without being necessary to specify
a certain parametrization. The mass asymmetry in binary cold fission of Th and
U isotopes is explained as the result of adding a phenomenological shell
correction to the liquid drop model deformation energy. Applications to binary,
ternary, and quaternary fission are outlined.Comment: 28 pages, 17 figure
Semi-spheroidal Quantum Harmonic Oscillator
A new single-particle shell model is derived by solving the Schr\"odinger
equation for a semi-spheroidal potential well. Only the negative parity states
of the component of the wave function are allowed, so that new magic
numbers are obtained for oblate semi-spheroids, semi-sphere and prolate
semi-spheroids. The semi-spherical magic numbers are identical with those
obtained at the oblate spheroidal superdeformed shape: 2, 6, 14, 26, 44, 68,
100, 140, ... The superdeformed prolate magic numbers of the semi-spheroidal
shape are identical with those obtained at the spherical shape of the
spheroidal harmonic oscillator: 2, 8, 20, 40, 70, 112, 168 ...Comment: 4 pages, 3 figures, 1 tabl
Cluster radioactivity in very heavy nuclei: a new perspective
Exotic cluster decay of very heavy nuclei is studied using the microscopic
nuclear potentials obtained by folding density dependent M3Y effective
interaction with the densities of the cluster and the daughter nuclei. The
microscopic nuclear potential, Coulomb interaction and the centrifugal barrier
arising out of spin-parity conservation are used to obtain the potential
between the cluster and the daughter nuclei. Half life values are calculated in
the WKB framework and the preformation factors are extracted. The latter values
are seen to have only a very weak dependence on the mass of the emitted
cluster.Comment: 4 pages including 2 table
Nuclear Half-Lives for Alpha Radioactivity of Elements with 100 Z 130
Theoretical estimates for the half lives of about 1700 isotopes of heavy
elements with Z from 100 to 130 are tabulated using theoretical Q-values. The
quantum mechanical tunneling probabilities are calculated within a WKB
framework using microscopic nuclear potentials. The microscopic nucleus-nucleus
potentials are obtained by folding the densities of interacting nuclei with a
density dependent M3Y (DDM3Y) effective nucleon-nucleon interaction. The
alpha-decay half lives calculated in this formalism using the experimental
Q-values were found to be in good agreement over a wide range of experimental
data spanning about twenty orders of magnitude. The theoretical Q-values used
for the present calculations are extracted from three different mass estimates
viz. Myers-Swiatecki [MS], Muntian-Hofmann-Patyk-Sobiczewski [M] and
Koura-Tachibana-Uno-Yamada [KUTY].Comment: 57 pages, 2 tables, 1 figur
On the alpha activity of natural tungsten isotopes
The indication for the alpha decay of 180-W with a half-life
T1/2=1.1+0.8-0.4(stat)+-0.3(syst)x10^18 yr has been observed for the first time
with the help of the super-low background 116-CdWO_4 crystal scintillators. In
conservative approach the lower limit on half-life of 180-W has been
established as T1/2>0.7x10^18 yr at 90% C.L. Besides, new T1/2 bounds were set
for alpha decay of 182-W, 183-W, 184-W and 186-W at the level of 10^20 yr.Comment: 16 pages, 8 figures, accepted in Phys. Rev.
The analysis of predictability of alpha-decay half-life formulae and the alpha partial half-lives of some exotic nuclei
The predictabilities of the three alpha-decay half-life formulae, the Royer
GLDM, the Viola-Seaborg and the Sobiczewski-Parkhomenko formulae, have been
evaluated by developing a method based on the ansatz of standard experimental
benchmarking. The coefficients of each formula were re-derived using the
reliable data of the alpha-standards nuclei. The modified formulae that
resulted were used to evaluate the accuracies of the formulae towards the
prediction of half-lives of a set of nuclides with well-studied alpha-
spectroscopic data as well as a set of exotic alpha-emitters. Further, a simple
linear optimization of the modified formulae allowed adjustments for the
insufficient statistics of the primary data set without changing the modified
formulae. While the three modified formulae showed equivalent results for all
the medium heavy nuclei except the odd-odd, the modified GLDM showed relatively
the best figures of merit for the odd-odd and superheavy nuclides.Comment: 16 pages, 4 tables, 2 figure
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