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Nomy-the wanderer
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Why fissions are mostly asymmetric rather than symmetric??
You mean something like 14 MeV? Well, certainly as the energy increases, the proportion of more symmetric fissions increases.Nomy-the wanderer said:First of all thanks for the reply...
I meant energies a lot higher than 1 Mev, with increasing energies the probability for symmetric fission gets higher...
Well, looking at the initiating event - one neutron 'hits' the U-235 nucleus - it is asymmetric! Even the U-235 is asymmetric because it has an odd number of neutrons.But can we get deeper, i mean what are these effects that leads to that fact??
Astronuc said:You mean something like 14 MeV? Well, certainly as the energy increases, the proportion of more symmetric fissions increases.
Well, looking at the initiating event - one neutron 'hits' the U-235 nucleus - it is asymmetric! Even the U-235 is asymmetric because it has an odd number of neutrons.
The most symmetric the reaction could be is if the neutron 'hits' the nucleus dead-on-center, but still the U-235 maintains some asymmetry. However, the probability of a precisely dead-on-center collision is quite small. Even then, there is the spin of the neutron which would necessarily make an interaction asymmetric.
In the center. :uhh: The center of mass, which may shift according to whatever resonances the nucleus is experiencing. Remember, there is a finite probability of 'spontaneous' fission.Where's that center??
Possibly. I'd have to dig around to find some expermental results which would verify that the 'shell model' is consistent with the distribution of fission products.Does the shell model explain this??
Because it has a preferred direction.OR why would the neutron spin make it necessarily asymmetric??
Astronuc said:In the center. :uhh: The center of mass, which may shift according to whatever resonances the nucleus is experiencing. Remember, there is a finite probability of 'spontaneous' fission.
Astronuc said:Because it has a preferred direction.
Thinking on the classic scale, if one has a spinning top and it collides as a result of translational motion, it scatters with a preferred direction (which is asymmetric) by virtue of the spin (angular momentum).
No - it is unlikely that a neutron would hit on-center. Also, think of Rutherford scattering of alpha particles or Compton scattering of gamma or X-rays, it is rare to get a perfect recoil in the incident direction and that indicates the relatively low probability of a particle colliding on a perfect on-center strike.Nomy-the wanderer said::rofl: yeah i know the center is the center, but i meant i can't pin point that center, and hence maybe i can't aim for a symmetric fission.
I was under the impression that the collision dynamics between the neutron and the nucleus had an insignificant effect on the way in which the nucleus fissions. This is because the kinetic energy of a thermal neutron is much less than the binding energy of that neutron upon capture by the nucleus. Am I wrong on that?Astronuc said:No - it is unlikely that a neutron would hit on-center. Also, think of Rutherford scattering of alpha particles or Compton scattering of gamma or X-rays, it is rare to get a perfect recoil in the incident direction and that indicates the relatively low probability of a particle colliding on a perfect on-center strike.
Well, certainly yes for thermal neutrons, and there are three outcomes, absorption with fission, absorption activation (gamma-emission) and scattering.Andrew Mason said:I was under the impression that the collision dynamics between the neutron and the nucleus had an insignificant effect on the way in which the nucleus fissions. This is because the kinetic energy of a thermal neutron is much less than the binding energy of that neutron upon capture by the nucleus. Am I wrong on that?
This is a very good question, and an interesting one.Astronuc said:Well, certainly yes for thermal neutrons, and there are three outcomes, absorption with fission, absorption activation (gamma-emission) and scattering.
The aborption of a thermal neutron, or any neutron, is asymmetric since it 'enters' (interacts) at a particular location at the nucleus.
I was thinking mainly of fast neutrons, which result in more symmetric fissions as is evidenced by the proportion of the f.p. spectrum near Z=46, i.e. midway between Z=36 and 56, which are common f.p.s
However, even spontaneous fissions are asymmetric which would indicated that internal resonances are asymmetric. Really what I was trying to explain is that there is essentially no way to achieve symmetry.
Asymmetric fission is a process in which an atomic nucleus splits into two unequal fragments rather than splitting symmetrically into two equal fragments. This process is typically observed in heavy atomic nuclei.
The asymmetry in fission is caused by the uneven distribution of protons and neutrons within the atomic nucleus. This uneven distribution leads to unequal forces acting on the nucleus, resulting in an unequal split during fission.
Asymmetric fission can result in the release of large amounts of energy, as well as the production of radioactive isotopes and radiation. It can also lead to the formation of new elements and isotopes.
Yes, asymmetric fission can occur naturally in certain heavy elements, such as uranium and plutonium. It is also a common process in nuclear reactors and nuclear weapons.
Scientists study asymmetric fission through various experiments, such as bombarding heavy nuclei with high-energy particles or using heavy ion accelerators. They also use theoretical models and computer simulations to better understand the process.