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121.
The correlations between the various parameters in the thermal neutron induced fission of 235U accompanied by long-range α-particles (LRA) have been measured employing a back-to-back gridded ionization chamber. Semiconductor detectors were placed symmetrically along the electric field direction of the chamber behind the thin windows of the collector plates for the measurement of the LRA energies. A distinguishing feature of the present method is that the angle between the fission fragments and the electric field direction (hence the direction of α-particle emission) is also determined electronically by the analysis of the coincident collector and grid pulses of the ionization chamber. About 5 × 105 LRA-accompanied fission events and about 2 × 106 binary fission events were recorded and analyzed to obtain a number of correlations of interest between the fragment mass, total kinetic energy, LRA energy and fragment-LRA angle. These experimental results are presented and discussed with regard to the emission mechanism of the LRA. 相似文献
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125.
A method is proposed to deduce the shell correction energy corresponding to the fission transition state shape of nuclei in
the mass region around 200, from an analysis of the first chance fission values of the ratio of fission to neutron widths,
(Γ
f
/Γ
n
)1. The method is applied to the typical case of the fissioning nucleus212Po, formed by alpha bombardment of208Pb. For the calculation of the neutron width, the level densities of the daughter nucleus after neutron emission were obtained
from a numerical calculation starting from shell model single particle energy level scheme. It is shown that with the use
of standard Fermi gas expression for the level densities of the fission transition state nucleus in the calculation of the
fission width, an apparent energy dependence of the fission barrier height is required to fit the experimental data. This
energy dependence, which arises from the excitation energy dependence of shell effects on level densities, can be used to
deduce the shell correction energy at the fission transition state point. It is found that in the case of212Po, the energy of the actual transition state point is higher than the energy of the liquid drop model (LDM) saddle point
by (3 ± 1) MeV, implying significant positive shell correction energy at the fission transition state. Further, the liquid
drop model value of level density parametera is found to be a few per cent smaller for the saddle point shape as compared to its spherical shape. 相似文献
126.
127.
Rita Kapoor 《Pramana》1980,14(3):209-217
Using the continuum theory of linear elasticity, the Huang diffuse scattering from interstitials in an hcp lattice has been
calculated to distinguish between the possible interstitial configurations. The symmetry of the lattice permits four such
configurations. In each case, the Huang diffuse scattering is averaged over all possible equivalent orientations (assumed
to be equally populated) of the defect configuration. The limitations of Huang diffuse scattering in discriminating between
defect configurations having the same long-range symmetry are discussed, considering the specia I cases of Mg and Zn. 相似文献
128.
129.
Kapoor MP Sinha AK Seelan S Inagaki S Tsubota S Yoshida H Haruta M 《Chemical communications (Cambridge, England)》2002,(23):2902-2903
Gold nanoparticles supported on highly hydrophobic ethane bridged Ti incorporated mesoporous organosilica are reported for enhanced vapor phase epoxidation of propene using H2 and O2. 相似文献
130.