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Are the halo nuclei of 6He and 8He the reason they have relatively long half-lives, compared to the other unstable isotopes of helium? XinaNicole ( talk) 23:54, 29 May 2011 (UTC)
Helium-2 is a hypothetical isotope of helium which according to theoretical calculations would have existed if the strong force had been 2% greater. This atom would have two protons without any neutrons. Would 2He be a stable isotope, or would it beta-decay to 2H in such a hypothetical universe? And if it were stable, does that mean 2H would beta-decay to 2He, since generally only a single nuclide of a given atomic mass is stable? XinaNicole ( talk) 02:19, 8 June 2011 (UTC)
It would be nice to reference old proton-proton low-energy (a few MeV) scattering experiments which might have revealed the resonance, or ruled it out for certain half-life ranges and resonance widths. The only half-life that I saw was much less than 10^-9 seconds. It would also be quite interesting if the diproton resonance were different inside a nucleus from free space. Johnm307 ( talk) 04:12, 29 October 2020 (UTC)
Johnm307 ( talk) 13:56, 6 April 2021 (UTC)
Should 2He ( diproton) be included in the table of isotopes? Whoop whoop pull up Bitching Betty | Averted crashes 13:56, 27 July 2011 (UTC)
If I ever find old published papers on proton-proton low-energy (a few MeV) scattering experiments, I will edit this myself. The 2He resonance would have been one of the first discovered. Johnm307 ( talk) 05:01, 6 October 2021 (UTC)
The intro now claims (since 19 October 2011) that He-2 has a half-life of 3x10-27 sec. Where does this number come from, please? I will mark it "citation needed".
Such a short half-life would seem to violate the speed limit of the universe. The time to separate two protons by a nuclear diameter of 10-15m cannot be less than 10-15m / c = 3 x 10-24s, so the claimed half-life implies that the protons are separating at 1000 times the speed of light.
Also there is a measurement problem here. Extremely short half-lives cannot be measured directly, but are deduced from the width of some resonance. Here the width would be ħ / 10-27s = 107 J = 1 TeV. Real measured widths are much smaller than that.
If these simple arguments are incorrect for some reason, we need to see the evidence.
Also in the section on He-2, the last two paragraphs are not properly referenced. One cannot just say that "The best evidence of He-2 was found in 2008 at the Istituto Nazionale di Fisica Nucleare, in Italy." We need a journal reference with author names, journal title with volume and pages and article title, and if possible an on-line link. Same for the Japanese and Russian work in the next paragraph. Does the 3x10-27s value come from one of these papers?? I don't know and I can't check if you don't tell me where the papers are. More "citation needed" tags. Dirac66 ( talk) 14:37, 19 December 2011 (UTC)
Today 2H was added to the table as a supposed "daughter isotope" of 2He, as well as 2 1H which was already in the table. However if 2He to 2H really occurred, it would be a beta-plus decay (positron emission). This is difficult to believe since beta decay is a weak interaction which results in half-lives much, much longer than the 3 x 10-27 s claimed by the table for 2He. The two other beta-decay nuclei in the table are examples: 807 ms for 6He and 119 ms for 8He, compared to half-lives near 10-21 s for the neutron-emitting nuclei 5He, 7He, 9He and 10He. If 2He falls apart into two protons in 3 x 10-27 s (or even 10-21 s), it does not have time to beta-decay.
Once again we need sources for 2He, which is not listed in the Nubase or Nudat sources at the end of the article. I plan to just delete 2He from the table if sources are not provided soon. Dirac66 ( talk) 20:00, 2 January 2012 (UTC)
The source is Giovanni Raciti, et. al in Physical Review Letters, 16 May 2008. It is not the astrophysical decay of the diproton (which incidentally might happen far faster than it takes the protons to separate by any distance, since they never do, inasmuch as one proton turns to a neutron by emitting a W which itself decays before it has gone even 0.1 fm). Instead, the Italians used a beam of neon-20 ions against beryllium foil. Some neon nuclei were stripped of two neutrons to Ne-18, which exited the foil and impacted lead foil. The collision excited Ne-18 nucleus into a instability. One of the decay modes for excited Ne-18 is double proton emission plus O-16. These two protons don't come out randomly, but in a single lump in a single direction-- in other words, bound together for a (very very) short time. From the angle between the two product protons after their agglomerate He-2 does break down, you can tell how long it must have held together. That was the number these guys got. S B H arris 06:00, 4 January 2012 (UTC)
Under the subtitle "Helium-2 (diproton)," the contributor suddenly introduces the name “Bradford” - as if we should all know who he is. Bradford is not a ‘Newton’ or an ‘Einstein.’ If he is not previously motioned, than his credentials should be stated to give validity to the article. At the very least, his full name (or initials) should precede his surname - try searching “Bradford” in the ‘search box.’ Manixx2a ( talk) 23:46, 3 July 2012 (UTC)
http://hal.archives-ouvertes.fr/docs/00/17/56/14/PDF/rpp.pdf Two-proton radioactivity - Bertram Blank ‡ and Marek P loszajczak †
Other is from RIKEN (?): http://fy.chalmers.se/~f2bmz/papers/korsheninnikov_2003_7h.pdf doi:10.1103/PhysRevLett.90.082501 p 2: "corresponds to our expectation that the two protons from the reaction p ( 8He; pp ) 7H can undergo final state interaction being emitted as a virtual singlet state 2He. This method was used in the study of 5H in the reaction p ( 6He; pp ) 5H [1]. \n When detecting the two protons by the RIKEN telescope, we obtain kinematically complete information about these two protons and, due to energy and momentum conservation in the reaction p (8 He; pp ) 7H, we can unambiguously reconstruct a mass of the residual system 7H. Also, we detected tritons and neutrons from the breakup of 7H using a downstream detection system consisting of a dipole magnet and plastic scintillators. This part of setup was the same as in our previous experiment described in Ref. [7]." ` a5b ( talk) 00:52, 19 July 2013 (UTC)
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Generally accepted that hyperdense solar plasma (in stars) consists of intermingled electrons and nucei. At the energy and neutrino levels of solar plasma, "neutron decay" would equilibrate with neutron creation. D2 would probably turn to Deuterium by electron capture not positron emission like vacuum chamber experiments show, however Deuterium plus 1.9MeV(see neutron source wiki) is proton plus neutron (deuterium fissions). Or at solar plasma pressure is the reaction favoring Deuterium. If it does it means Deuterium >> Helium4 is a faster reaction. TaylorLeem ( talk) 19:05, 27 June 2020 (UTC)
Hello everyone!
I'm putting this message up to ask whether I should remove the row for helium-2 from the table, because it is currently not listed in AME2020. If the consensus is to retain the value, could someone please explain (if possible) where the current value comes from/how to calculate it? Also, while on the topic: what's the current scientific consensus and research regarding helium-2 at the moment?
(Sorry for the poor formatting)
MeasureWell ( talk) 07:22, 9 October 2021 (UTC)
If the daughter isotope of the rarer Helium-6 decay mode is Helium-4, isn't it double neutron decay? Similarly, if the daughter isotope of the rarest decay mode of Helium-8 is Helium-5, isn't it triple neutron decay? Why are these decay modes indicating simultaneous electron/proton emission with the beta decay symbol when the only difference between the parent and daughter nuclides across these decay modes is neutron count?
As far as I'm aware, the proper format for other isotope lists is Xn, where X is number of emitted neutrons ( see Isotopes of Hydrogen) - deuteron and triton emission aren't shorthand for 2n and 3n decay modes, they're a separate decay type entirely (unless I'm misunderstanding something, they're more like alpha emission; they're referring to the emission of entire deuterium and tritium nuclei). InkTide ( talk) 12:21, 6 April 2023 (UTC)
The article can be found here. 2A04:CEC0:10EE:D636:ADA9:C82B:7392:6BE ( talk) 11:08, 7 February 2024 (UTC)
Since the decay mode of 6Be is 2p, could the two protons be considered as 2He in an instant? 2A01:E34:EC74:7170:C92D:3550:651:9FE3 ( talk) 16:47, 5 May 2024 (UTC)
![]() | This ![]() It is of interest to the following WikiProjects: | |||||||||||||
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Are the halo nuclei of 6He and 8He the reason they have relatively long half-lives, compared to the other unstable isotopes of helium? XinaNicole ( talk) 23:54, 29 May 2011 (UTC)
Helium-2 is a hypothetical isotope of helium which according to theoretical calculations would have existed if the strong force had been 2% greater. This atom would have two protons without any neutrons. Would 2He be a stable isotope, or would it beta-decay to 2H in such a hypothetical universe? And if it were stable, does that mean 2H would beta-decay to 2He, since generally only a single nuclide of a given atomic mass is stable? XinaNicole ( talk) 02:19, 8 June 2011 (UTC)
It would be nice to reference old proton-proton low-energy (a few MeV) scattering experiments which might have revealed the resonance, or ruled it out for certain half-life ranges and resonance widths. The only half-life that I saw was much less than 10^-9 seconds. It would also be quite interesting if the diproton resonance were different inside a nucleus from free space. Johnm307 ( talk) 04:12, 29 October 2020 (UTC)
Johnm307 ( talk) 13:56, 6 April 2021 (UTC)
Should 2He ( diproton) be included in the table of isotopes? Whoop whoop pull up Bitching Betty | Averted crashes 13:56, 27 July 2011 (UTC)
If I ever find old published papers on proton-proton low-energy (a few MeV) scattering experiments, I will edit this myself. The 2He resonance would have been one of the first discovered. Johnm307 ( talk) 05:01, 6 October 2021 (UTC)
The intro now claims (since 19 October 2011) that He-2 has a half-life of 3x10-27 sec. Where does this number come from, please? I will mark it "citation needed".
Such a short half-life would seem to violate the speed limit of the universe. The time to separate two protons by a nuclear diameter of 10-15m cannot be less than 10-15m / c = 3 x 10-24s, so the claimed half-life implies that the protons are separating at 1000 times the speed of light.
Also there is a measurement problem here. Extremely short half-lives cannot be measured directly, but are deduced from the width of some resonance. Here the width would be ħ / 10-27s = 107 J = 1 TeV. Real measured widths are much smaller than that.
If these simple arguments are incorrect for some reason, we need to see the evidence.
Also in the section on He-2, the last two paragraphs are not properly referenced. One cannot just say that "The best evidence of He-2 was found in 2008 at the Istituto Nazionale di Fisica Nucleare, in Italy." We need a journal reference with author names, journal title with volume and pages and article title, and if possible an on-line link. Same for the Japanese and Russian work in the next paragraph. Does the 3x10-27s value come from one of these papers?? I don't know and I can't check if you don't tell me where the papers are. More "citation needed" tags. Dirac66 ( talk) 14:37, 19 December 2011 (UTC)
Today 2H was added to the table as a supposed "daughter isotope" of 2He, as well as 2 1H which was already in the table. However if 2He to 2H really occurred, it would be a beta-plus decay (positron emission). This is difficult to believe since beta decay is a weak interaction which results in half-lives much, much longer than the 3 x 10-27 s claimed by the table for 2He. The two other beta-decay nuclei in the table are examples: 807 ms for 6He and 119 ms for 8He, compared to half-lives near 10-21 s for the neutron-emitting nuclei 5He, 7He, 9He and 10He. If 2He falls apart into two protons in 3 x 10-27 s (or even 10-21 s), it does not have time to beta-decay.
Once again we need sources for 2He, which is not listed in the Nubase or Nudat sources at the end of the article. I plan to just delete 2He from the table if sources are not provided soon. Dirac66 ( talk) 20:00, 2 January 2012 (UTC)
The source is Giovanni Raciti, et. al in Physical Review Letters, 16 May 2008. It is not the astrophysical decay of the diproton (which incidentally might happen far faster than it takes the protons to separate by any distance, since they never do, inasmuch as one proton turns to a neutron by emitting a W which itself decays before it has gone even 0.1 fm). Instead, the Italians used a beam of neon-20 ions against beryllium foil. Some neon nuclei were stripped of two neutrons to Ne-18, which exited the foil and impacted lead foil. The collision excited Ne-18 nucleus into a instability. One of the decay modes for excited Ne-18 is double proton emission plus O-16. These two protons don't come out randomly, but in a single lump in a single direction-- in other words, bound together for a (very very) short time. From the angle between the two product protons after their agglomerate He-2 does break down, you can tell how long it must have held together. That was the number these guys got. S B H arris 06:00, 4 January 2012 (UTC)
Under the subtitle "Helium-2 (diproton)," the contributor suddenly introduces the name “Bradford” - as if we should all know who he is. Bradford is not a ‘Newton’ or an ‘Einstein.’ If he is not previously motioned, than his credentials should be stated to give validity to the article. At the very least, his full name (or initials) should precede his surname - try searching “Bradford” in the ‘search box.’ Manixx2a ( talk) 23:46, 3 July 2012 (UTC)
http://hal.archives-ouvertes.fr/docs/00/17/56/14/PDF/rpp.pdf Two-proton radioactivity - Bertram Blank ‡ and Marek P loszajczak †
Other is from RIKEN (?): http://fy.chalmers.se/~f2bmz/papers/korsheninnikov_2003_7h.pdf doi:10.1103/PhysRevLett.90.082501 p 2: "corresponds to our expectation that the two protons from the reaction p ( 8He; pp ) 7H can undergo final state interaction being emitted as a virtual singlet state 2He. This method was used in the study of 5H in the reaction p ( 6He; pp ) 5H [1]. \n When detecting the two protons by the RIKEN telescope, we obtain kinematically complete information about these two protons and, due to energy and momentum conservation in the reaction p (8 He; pp ) 7H, we can unambiguously reconstruct a mass of the residual system 7H. Also, we detected tritons and neutrons from the breakup of 7H using a downstream detection system consisting of a dipole magnet and plastic scintillators. This part of setup was the same as in our previous experiment described in Ref. [7]." ` a5b ( talk) 00:52, 19 July 2013 (UTC)
Hello fellow Wikipedians,
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(last update: 5 June 2024).
Cheers.— InternetArchiveBot ( Report bug) 14:14, 15 April 2017 (UTC)
Generally accepted that hyperdense solar plasma (in stars) consists of intermingled electrons and nucei. At the energy and neutrino levels of solar plasma, "neutron decay" would equilibrate with neutron creation. D2 would probably turn to Deuterium by electron capture not positron emission like vacuum chamber experiments show, however Deuterium plus 1.9MeV(see neutron source wiki) is proton plus neutron (deuterium fissions). Or at solar plasma pressure is the reaction favoring Deuterium. If it does it means Deuterium >> Helium4 is a faster reaction. TaylorLeem ( talk) 19:05, 27 June 2020 (UTC)
Hello everyone!
I'm putting this message up to ask whether I should remove the row for helium-2 from the table, because it is currently not listed in AME2020. If the consensus is to retain the value, could someone please explain (if possible) where the current value comes from/how to calculate it? Also, while on the topic: what's the current scientific consensus and research regarding helium-2 at the moment?
(Sorry for the poor formatting)
MeasureWell ( talk) 07:22, 9 October 2021 (UTC)
If the daughter isotope of the rarer Helium-6 decay mode is Helium-4, isn't it double neutron decay? Similarly, if the daughter isotope of the rarest decay mode of Helium-8 is Helium-5, isn't it triple neutron decay? Why are these decay modes indicating simultaneous electron/proton emission with the beta decay symbol when the only difference between the parent and daughter nuclides across these decay modes is neutron count?
As far as I'm aware, the proper format for other isotope lists is Xn, where X is number of emitted neutrons ( see Isotopes of Hydrogen) - deuteron and triton emission aren't shorthand for 2n and 3n decay modes, they're a separate decay type entirely (unless I'm misunderstanding something, they're more like alpha emission; they're referring to the emission of entire deuterium and tritium nuclei). InkTide ( talk) 12:21, 6 April 2023 (UTC)
The article can be found here. 2A04:CEC0:10EE:D636:ADA9:C82B:7392:6BE ( talk) 11:08, 7 February 2024 (UTC)
Since the decay mode of 6Be is 2p, could the two protons be considered as 2He in an instant? 2A01:E34:EC74:7170:C92D:3550:651:9FE3 ( talk) 16:47, 5 May 2024 (UTC)