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Nuclear physics is complicated and the calculations are difficult, so a lot of what we know is based on observation more than calculations.
originally posted by: pteridine
a reply to: Dineutron
This is one part (of many) that puzzles me. "A possible idea is to find a suitable nuclear species that has dineutrons floating near or on the surface of a core nucleus"
Does this imply a nucleus composed of a particle soup? It would seem that with everything else in the atomic world having a structure that the nucleus should have one also.
Physicists in the US claim to have witnessed, for the first time, the emission of a neutron pair in the decay of an atomic nucleus. Such “dineutron” decay could extend our understanding of the strong force, which is responsible for holding nuclei together, and the processes taking place in neutron stars...
The obvious place to begin searching for dineutron decay is in nuclei that contain too many neutrons – that is, those nuclei that would want to lose at least two neutrons in order to become more stable. Such neutron-rich nuclei tend to decay one neutron at a time, rather than two at once. But not all nuclei opt for a step-by-step decay: beryllium-16 does not readily emit a single neutron because that would leave a nucleus of beryllium-15, which is more unstable.
Spyrou’s group examined beryllium-16 for dineutron decay. They created the isotope at the National Superconducting Cyclotron Laboratory at Michigan State University by removing a single proton from a boron-17 beam. Immediately, the resultant beryllium-16 decayed into two neutrons. After examining the energy and position information for all three particles – the two neutrons and the remaining beryllium-14 nucleus – the researchers calculated that the two neutrons were emitted together and in the same direction.
Spyrou says that the direction is important for labelling the process as dineutron decay. If the neutrons had been left the nucleus separately, she says, the angle between them would have been almost random.
“Ferreting out “true events
Bob Charity, a chemist specializing in nuclear structure and reactions at Washington University in St Louis, US, thinks the results are impressive. “A single neutron may interact with one part of a detector and in the process scatter and then interact with another part, making it hard to differentiate a single-neutron event from a true two-neutron event,” he says. “The experimental effort…should be praised for ferreting out the two-neutron events from this background of ‘fake’ two-neutron events.”
However, some scientists, including Charity, are sceptical that the dineutron should be considered a well-defined entity. Since the emitted neutrons are already correlated inside the beryllium nucleus’s halo, these scientists say, they are likely to be correlated outside, too – but that does not mean the neutrons are truly bound together.
“I am not convinced that what they see is a new type of particle,” Marek Pfützner told physicsworld.com. Pfützner is a nuclear physicist at the University of Warsaw in Poland and believes that the concept of a dineutron is “a very simplified way to describe the data, which is used a when more detailed and rigorous description is missing”.
I don't think anybody can tell you with certainty what the nuclear structure is. We have different models and they have different strengths and weaknesses but as far as I know, none of the models are accurate enough to explain all observations.
originally posted by: pteridine
a reply to: Arbitrageur
Would having a defined nuclear structure help or hinder this observation? It would seem that with a nucleus soup of particles, having both neutrons with the same energy and vector would dictate the existence of a dineutron. With a structured nucleus, this becomes less compelling.
The dineutron, containing two neutrons, was unambiguously observed in 2012 in the decay of beryllium-16.[8][9]It is not a bound particle, but had been proposed as an extremely short-lived resonance state produced by nuclear reactions involving tritium. It has been suggested to have a transitory existence in nuclear reactions produced by helions (helium 3 nuclei, completely ionised) that result in the formation of a proton and a nucleus having the same atomic number as the target nucleus but a mass number two units greater. The dineutron hypothesis had been used in nuclear reactions with exotic nuclei for a long time.[10] Several applications of the dineutron in nuclear reactions can be found in review papers.[11] Its existence has been proven to be relevant for nuclear structure of exotic nuclei.[12] A system made up of only two neutrons is not bound, though the attraction between them is very nearly enough to make them so.
What is important I think is that there isn't enough binding energy between two neutrons to really bind them together, but, there is almost enough. So maybe it's the "almost enough" which helps keep the neutrons together as they are ejected until they are detected, in what has been proposed as "an extremely short-lived resonance state".
I have no idea what you're trying to say with your sentence fragment and three links. Perhaps the reason few seem to talk about Pauling's model specifically is because "Pauling promised that the quantum mechanical calculations enabled by his polyspheron theory were essentially the same as those that had been made using various other models in the past."
originally posted by: Dineutron
What is important I think is that there isn't enough binding energy between two neutrons to really bind them together, but, there is almost enough. So maybe it's the "almost enough" which helps keep the neutrons together as they are ejected until they are detected, in what has been proposed as "an extremely short-lived resonance state".
In the spheron model of the nucleus (Linus Pauling) :
scarc.library.oregonstate.edu...
Spheron model:
www.pnas.org...
en.wikipedia.org...
In an effort to assure the scientific rank and file that he was not seeking to upend their entire understanding of nuclear physics, Pauling promised that the quantum mechanical calculations enabled by his polyspheron theory were essentially the same as those that had been made using various other models in the past.
Perhaps unwittingly, this assurance left many colleagues within the field wondering why Pauling was bothering to develop this theory at all. For many physicists, Pauling’s work seemed redundant, or perhaps merely an attempt to change the names of existing terms to new ones that fit more elegantly into Pauling’s conceptual framework of atomic structure.
originally posted by: Arbitrageur
I don't think anybody can tell you with certainty what the nuclear structure is. We have different models and they have different strengths and weaknesses but as far as I know, none of the models are accurate enough to explain all observations.
originally posted by: pteridine
a reply to: Arbitrageur
Would having a defined nuclear structure help or hinder this observation? It would seem that with a nucleus soup of particles, having both neutrons with the same energy and vector would dictate the existence of a dineutron. With a structured nucleus, this becomes less compelling.
What is important I think is that there isn't enough binding energy between two neutrons to really bind them together, but, there is almost enough. So maybe it's the "almost enough" which helps keep the neutrons together as they are ejected until they are detected, in what has been proposed as "an extremely short-lived resonance state".
Neutronium
The dineutron, containing two neutrons, was unambiguously observed in 2012 in the decay of beryllium-16.[8][9]It is not a bound particle, but had been proposed as an extremely short-lived resonance state produced by nuclear reactions involving tritium. It has been suggested to have a transitory existence in nuclear reactions produced by helions (helium 3 nuclei, completely ionised) that result in the formation of a proton and a nucleus having the same atomic number as the target nucleus but a mass number two units greater. The dineutron hypothesis had been used in nuclear reactions with exotic nuclei for a long time.[10] Several applications of the dineutron in nuclear reactions can be found in review papers.[11] Its existence has been proven to be relevant for nuclear structure of exotic nuclei.[12] A system made up of only two neutrons is not bound, though the attraction between them is very nearly enough to make them so.
Maybe. There was a proposed resonance mode, but I don't really understand that, and I'm not sure if that proposed method is confirmed.
originally posted by: pteridine
If there is not enough binding energy available to produce a stable particle, is there enough for one neutron to drag another along?
In the case of beryllium-16 decaying into beryllium-14, the reason it does so is because beryllium-15 is even more unstable than beryllium-16. So you could be right about that in the case of beryllium 16 decay into beryllium 15, in fact I couldn't find any mention of that decay mode. It seems beryllium-15 and beryllium-16 both decay to beryllium-14.
This would imply that the drag along energy is greater than that binding the neutron to the nucleus.
originally posted by: mbkennel
a reply to: BASSPLYR
I think it was referring to gravitational waves with the same frequency as x-rays would have in electromagnetism.
But how on earth would a HFGW generator work with actual physics known to experimental reality, and how would it have any engineering useful capability given the extremely small value of G vs any other force?