Isotope Dependence of Superheavy Nucleus Formation Cross Section

2006 ◽  
Vol 23 (6) ◽  
pp. 1437-1440 ◽  
Author(s):  
Liu Zu-Hua ◽  
Bao Jing-Dong
Keyword(s):  
Cross Section ◽  
Superheavy Nucleus ◽  
Formation Cross Section ◽  
Nucleus Formation

scholarly journals Multiband coupling and nuclear softness in optical model calculations for even-even and odd-A actinides

2020 ◽  
Vol 239 ◽  
pp. 03003
Author(s):  
Dmitry Martyanov ◽  
Efrem Soukhovitskiĩ ◽  
Roberto Capote ◽  
José M. Quesada ◽  
Satoshi Chiba
Keyword(s):  
Cross Section ◽  
Compound Nucleus ◽  
Optical Model ◽  
Incident Neutron ◽  
Model Calculations ◽  
Formation Cross Section ◽  
Nucleus Formation ◽  
Coupled Channels ◽  
Compound Nucleus Formation ◽  
The Impact

A new dispersive multiband coupled channels optical model with soft-rotator “effective” deformations is proposed to describe nucleon scattering on even-even and odd-A actinides. The impact of the introduction of axial and non-axial dynamical deformations that describe nuclear softness is discussed. Softness and multiband coupling are shown to change compound-nucleus formation cross section by up to ≈ 10% for incident neutron energies below 1 MeV.

COMPOUND NUCLEUS FORMATION IN NITROGEN–OXYGEN AND OXYGEN–OXYGEN REACTIONS

1962 ◽  
Vol 40 (1) ◽  
pp. 139-149
Author(s):  
W. A. Cartledge
Keyword(s):  
Cross Section ◽  
Compound Nucleus ◽  
Center Of Mass ◽  
Branching Ratio ◽  
Nuclear Interaction ◽  
Experimental Cross Section ◽  
Interaction Radius ◽  
Nucleus Formation ◽  
Experimental Cross ◽  
Compound Nucleus Formation

The experimental cross section for the reaction O16(N14,2p)Al28 is compared with the predictions of the square-well model of compound nucleus formation over the range 6.3 to 12 Mev (center of mass energy). The branching ratio is estimated from the experimental cross section for the comparison reaction Si29(p,2p)Al28 over the same range of excitation in the compound nucleus P30*. It is found that the branching ratio probably increases from about 10% to 20%, which requires the nuclear interaction radius for N14 + O16 to decrease from about 8.5 to 7.5 fermis as the energy is increased over this range.Because of the similarity in mass and observed charge distributions in N14 and O16, the interaction radius for compound nucleus formation in a collision between two oxygen nuclei is probably also similar and in the range 8.0 to 9.1 fermis at energies far below the Coulomb barrier. A consequence of this result is that oxygen ions, which may be present in the cores of sufficiently developed red giant stars, will be destroyed by O16 + O16 collisions in about 105 years and 1 year respectively, at temperatures in the vicinity of 13.0 and 18.5 × 108 °K.

The Scattering of Positrons by Helium: Total Cross Sections up to 270 eV

1975 ◽  
Vol 53 (10) ◽  
pp. 962-967 ◽  
Author(s):  
B. Jaduszliwer ◽  
A. Nakashima ◽  
D. A. L. Paul
Keyword(s):  
Energy Range ◽  
Cross Section ◽  
Cross Sections ◽  
Born Approximation ◽  
Reasonable Agreement ◽  
Experimental Results ◽  
Formation Cross Section ◽  
Sum Rule ◽  
Total Cross Sections ◽  
High Energies

The total cross sections for the scattering of positrons by helium have been measured by the method of transmission in the 16 to 270 eV energy range. The experimental results are higher than those of Canter et al. but are in reasonable agreement with recent results of Griffith et al., and at high energies tend towards Born approximation calculations. The integral of the cross section over positron momentum is smaller than the sum rule estimate made by Bransden et al. A tentative value of (0.034 ± 0.017)πa02 is assigned to the positronium formation cross section at threshold.

scholarly journals X-ray photolysis of CH3COCH3 ice: implications for the radiation effects of compact objects towards astrophysical ices

2020 ◽  
Vol 498 (1) ◽  
pp. 689-701 ◽  
Author(s):  
G A Carvalho ◽  
S Pilling
Keyword(s):  
Cross Section ◽  
Time Scales ◽  
Chemical Equilibrium ◽  
Radiation Effects ◽  
Broad Band ◽  
Compact Objects ◽  
X Rays ◽  
Formation Cross Section ◽  
X Ray ◽  
Molecular Abundances

ABSTRACT In this study, we employed broad-band X-rays (6–2000 eV) to irradiate the frozen acetone CH3COCH3, at the temperature of 12 K, with different photon fluences up to 2.7 × 1018 photons cm−2. Here, we consider acetone as a representative complex organic molecule (COM) present on interstellar ice grains. The experiments were conduced at the Brazilian Synchrotron facility (LNLS/CNPEN) employing infrared spectroscopy (FTIR) to monitor chemical changes induced by radiation in the ice sample. We determined the effective destruction cross-section of the acetone molecule and the effective formation cross-section for daughter species. Chemical equilibrium, obtained for fluence 2 × 1018 photons cm−2, and molecular abundances at this stage were determined, which also includes the estimates for the abundance of unknown molecules, produced but not detected, in the ice. Time-scales for ices, at hypothetical snow line distances, to reach chemical equilibrium around several compact and main-sequence X-ray sources are given. We estimate time-scales of 18 d, 3.6 and 1.8 months, 1.4 × 109–6 × 1011 yr, 600 and 1.2 × 107 yr, and 107 yr, for the Sun at 5 au, for O/B stars at 5 au, for white dwarfs at 1 LY, for the Crab pulsar at 2.25 LY, for Vela pulsar at 2.25 LY, and for Sagittarius A* at 3 LY, respectively. This study improves our current understanding about radiation effects on the chemistry of frozen material, in particular, focusing for the first time, the effects of X-rays produced by compact objects in their eventual surrounding ices.

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