365 research outputs found
Microscopic study of 240Pu, mean-field and beyond
The influence of exact angular-momentum projection and configuration mixing
on properties of a heavy, well-deformed nucleus is discussed for the example of
Pu240. Starting from a self-consistent model using Skyrme interactions, we
analyze the resulting modifications of the deformation energy, the fission
barrier height, the excitation energy of the superdeformed minimum associated
with the fission isomer, the structure of the lowest rotational bands with
normal deformation and superdeformation, and the corresponding quadrupole
moments and transition moments. We present results obtained with the Skyrme
interactions SLy4 and SLy6, which have slightly different surface tensions.Comment: 7 pages REVTEX4, 4 figures. accepted for publication in Phys. Rev.
Gender roles on social networking sites: Investigating reciprocal relationships between Dutch adolescents' hypermasculinity and hyperfemininity and sexy online self-presentations
Adolescents' Sexual Media Use and Willingness to Engage in Casual Sex: Differential Relations and Underlying Processes
Sexually explicit Internet material and adolescents' sexual performance orientation: The mediating roles of enjoyment and perceived utility
The contrasting fission potential-energy structure of actinides and mercury isotopes
Fission-fragment mass distributions are asymmetric in fission of typical
actinide nuclei for nucleon number in the range
and proton number in the range . For somewhat
lighter systems it has been observed that fission mass distributions are
usually symmetric. However, a recent experiment showed that fission of
Hg following electron capture on Tl is asymmetric. We calculate
potential-energy surfaces for a typical actinide nucleus and for 12 even
isotopes in the range Hg--Hg, to investigate the similarities
and differences of actinide compared to mercury potential surfaces and to what
extent fission-fragment properties, in particular shell structure, relate to
the structure of the static potential-energy surfaces. Potential-energy
surfaces are calculated in the macroscopic-microscopic approach as functions of
fiveshape coordinates for more than five million shapes. The structure of the
surfaces are investigated by use of an immersion technique. We determine
properties of minima, saddle points, valleys, and ridges between valleys in the
5D shape-coordinate space. Along the mercury isotope chain the barrier heights
and the ridge heights and persistence with elongation vary significantly and
show no obvious connection to possible fragment shell structure, in contrast to
the actinide region, where there is a deep asymmetric valley extending from the
saddle point to scission. The mechanism of asymmetric fission must be very
different in the lighter proton-rich mercury isotopes compared to the actinide
region and is apparently unrelated to fragment shell structure. Isotopes
lighter than Hg have the saddle point blocked from a deep symmetric
valley by a significant ridge. The ridge vanishes for the heavier Hg isotopes,
for which we would expect a qualitatively different asymmetry of the fragments.Comment: 8 pages, 9 figure
Characterization of a Plain Broadband Textile PIFA
Bandwidth characteristic of a wearable antenna is one of the major factors in determining its usability on the human body. In this work, a planar inverted-F antenna (PIFA) structure is proposed to achieve a large bandwidth to avoid serious antenna reflection coefficient detuning when placed in proximity of the body. The proposed structure is designed based on a simple structure, in order to provide practicality in application and maintain fabrication simplicity. Two different types of conductive textiles, namely Pure Copper Polyester Taffeta Fabric (PCPTF) and ShieldIt, are used in order to proof its concept, in comparison with a metallic antenna made from copper foil. The design is spaced and fabricated using a 6 mm thick fleece fabric. To cater for potential fabrication and material measurement inaccuracies, both antennas' performance are also investigated and analyzed with varying physical and material parameters. From this investigation, it is found that the proposed structure's extended bandwidth enabled the antenna to function with satisfactory on-body reflection coefficients, despite unavoidable gain and efficiency reduction
Fusion of radioactive Sn with Ni
Evaporation residue and fission cross sections of radioactive Sn on
Ni were measured near the Coulomb barrier. A large sub-barrier fusion
enhancement was observed. Coupled-channel calculations including inelastic
excitation of the projectile and target, and neutron transfer are in good
agreement with the measured fusion excitation function. When the change in
nuclear size and shift in barrier height are accounted for, there is no extra
fusion enhancement in Sn+Ni with respect to stable Sn+Ni.
A systematic comparison of evaporation residue cross sections for the fusion of
even Sn and Sn with Ni is presented.Comment: 9 pages, 11 figure
Calculations of Branching Ratios for Radiative-Capture, One-Proton, and Two-Neutron Channels in the Fusion Reaction Bi+Zn
We discuss the possibility of the non-one-neutron emission channels in the
cold fusion reaction Zn + Bi to produce the element Z=113. For
this purpose, we calculate the evaporation-residue cross sections of
one-proton, radiative-capture, and two-neutron emissions relative to the
one-neutron emission in the reaction Zn + Bi. To estimate the
upper bounds of those quantities, we vary model parameters in the calculations,
such as the level-density parameter and the height of the fission barrier. We
conclude that the highest possibility is for the 2n reaction channel, and its
upper bounds are 2.4 and at most less than 7.9% with unrealistic parameter
values, under the actual experimental conditions of [J. Phys. Soc. Jpn. {\bf
73} (2004) 2593].Comment: 6 pages, 4 figure
The interaction of 11Li with 208Pb
Background: 11Li is one of the most studied halo nuclei. The fusion of 11Li
with 208Pb has been the subject of a number of theoretical studies with widely
differing predictions, ranging over four orders of magnitude, for the fusion
excitation function.
Purpose: To measure the excitation function for the 11Li + 208Pb reaction.
Methods: A stacked foil/degrader assembly of 208Pb targets was irradiated
with a 11Li beam producing center of target beam energies from above barrier to
near barrier energies (40 to 29 MeV). The intensity of the 11Li beam (chopped)
was 1250 p/s and the beam on-target time was 34 hours. The alpha-decay of the
stopped evaporation residues was detected in a alpha-detector array at each
beam energy in the beam-off period (the beam was on for <= 5 ns and then off
for 170 ns).
Results: The 215At evaporation residues were associated with the fusion of
11Li with 208Pb. The 213,214At evaporation residues were formed by the breakup
of 11Li into 9Li + 2n, with the 9Li fusing with 208Pb. The 214At evaporation
residue appears to result from a "quasi-breakup" process.
Conclusions: Most of 11Li + 208Pb interactions lead to breakup with a small
fraction (<= 11%) leading to complete fusion.Comment: 25 pages, 11 figure
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