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Elusive di-proton revealedElusive di-proton revealed!


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(From New Scientist magazine, 04 November 2000.)

 

After a 40-year search, physicists have finally caught a glimpse of a rare form of radioactivity in which a nucleus spits out two protons at the same time.

 

The researchers believe the protons emerge stuck together as a pair--a unique configuration that will give a an important insight into the strong nuclear force that glues the particles in nuclei together. "This might provide us with a new way of looking at how nucleons interact," says Philip Woods, a nuclear physicist at the University of Edinburgh.

 

There are only a few ways in which unstable nuclei can transform themselves. They can either split apart or chuck out one of a small repertoire of particles, such as a neutron or a helium-4 nucleus--two protons and two neutrons. Decades ago, nuclear theorists predicted that this list should include di-proton decay, where two protons fly away stuck together as a helium-2 nucleus. But researchers could never be sure they were seeing such decays.

 

Physicists hope that by studying di- proton decay they will learn about the arrangement of protons inside the nucleus and how they escape as a pair. "It could tell us something about the strength of the pairing interaction in the strong nuclear force," says Bertram Blank of the Centre for Nuclear Studies in Bordeaux-Gradignan, France. "Right now we know very little about this."

 

Researchers have known since the 1980s that decaying radioactive nuclei emit two protons. But they could not confirm whether they came out at the same time, or just very quickly one after the other. Now a team using the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory in Tennessee has found a way to make sequential emission impossible.

 

They did this by firing a beam of fluorine-17 atoms at a thin plastic surface rich in hydrogen atoms. The fluorine grabs hydrogen from the plastic and is converted into neon-18, which then decays to oxygen-16. If the neon-18 is in a particular excited state, it is energetically impossible for it to decay by emitting only one proton. "That's the clever part," says team member Alfredo Galindo-Uribarri. "There's no intermediate step of the ladder." So the atoms are forced to emit two protons at once to become oxygen-16.

 

There is still a possibility that the protons could be leaving simultaneously but separately in a process called democratic emission (see below). Since these protons probably weren't "living together" inside the nucleus, says Galindo-Uribarri, they would tell us little about the strong nuclear force. But his colleague Jorge Gomez del Campo has few doubts. "I'm convinced we're seeing helium-2 emission."

 

Galindo-Uribarri says they'll need a bigger detector--due to be up and running early next year--to decide for sure. The team has submitted a paper to Physical Review Letters.

 

Nicola Jones

 

From New Scientist magazine, 04 November 2000.

 

 

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Thank you for the information!

 

I can't imagine how Helium-2 can be emitted unless it's extremely short-lived. I think this because:

 

1) Helium-2 is not listed as an existing isotope of Helium (Helium-3 and Helium-4 are listed) meaning that this is not found normally in nature and if this was a by-product of radioactive decay with any length to its lifetime we would of detected it before this.

 

2) The strong force must overpower the electromagnetic force to hold two protons together and the distance the two protons must be from each other would have to be super close. The electromagnetic force is an inverse square force whereas the strong force is a combination of inverse fifth and inverse tenth force which gives the possibility for the isotope; but electromagnetism is so much stronger than the other forces just on a basic level that these particles must get extremely close before electromagnetism can be overwhelmed.

 

I understand why some are skeptical.

 

------------------

 

Victor Sciortino

 

 

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  • 13 years later...

New information as in 2014:

 

"Another evidence of 2He was found in 2008 at the Istituto Nazionale di Fisica Nucleare, in Italy. A beam of 20Ne ions was collided into a foil of beryllium. In this collision some of the neon ended up as 18Ne nuclei. These same nuclei then collided with a foil of lead. The second collision had the effect of exciting the 18Ne nucleus into a highly unstable condition. As in the earlier experiment at Oak Ridge, the 18Ne nucleus decayed into an 16O nucleus, plus two protons detected exiting from the same direction. The new experiment showed that the two protons were initially ejected together, correlated in a quasibound 1S configuration, before decaying into separate protons much less than a billionth of a second later."

 

Source: Isotopes of helium - Wikipedia, the free encyclopedia

 

 

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New information as in 2014:"Another evidence of 2He was found in 2008 at the Istituto Nazionale di Fisica Nucleare, in Italy. A beam of 20Ne ions was collided into a foil of beryllium. In this collision some of the neon ended up as 18Ne nuclei. These same nuclei then collided with a foil of lead. The second collision had the effect of exciting the 18Ne nucleus into a highly unstable condition. As in the earlier experiment at Oak Ridge, the 18Ne nucleus decayed into an 16O nucleus, plus two protons detected exiting from the same direction. The new experiment showed that the two protons were initially ejected together, correlated in a quasibound 1S configuration, before decaying into separate protons much less than a billionth of a second later."

 

Source: Isotopes of helium - Wikipedia, the free encyclopedia

servantx, you are truly prone to digging up some old threads! I've done the same on occasion, though :)

 

 

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Doesn't molecular orbital theory already account for 2He?Why is this news?

No. In quantum physics molecular valence is part of QED. But this is inside the nucleus and involves QCD...quarks, confinement and, yes, electrodynamics when we consider the Coulomb Force between the protons. In any case its much more complex than QED. Two protons in a bound state absent a neutron or two is a tough situation to explain. Electrodynamically they should blow apart at very high velocity as in a nuclear fission. In standard electroweak theory one proton should beta decay to a neutron as in P-P solar fusion.

 

I did some research yesterday and there are very few free articles on di-proton research. Most of the papers are dated in the 1960's and a few more in the 1990's but not much thereafter.

 

 

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In standard electroweak theory one proton should beta decay to a neutron .

I would think it is the Neutron that more often decays to the less massed Proton, perhaps with electron and associated gamma.

 

Proton decay - Wikipedia, the free encyclopedia

 

This all sounds like "theory" to me, that can only occur with fusion, I cant seem to find it as part of the "standard" electroweak theory.

 

" Hans Bethe proposed that one of the protons could beta decay into a neutron via the weak interaction during the brief moment of fusion"

 

Proton–proton chain reaction - Wikipedia, the free encyclopedia

 

More detail on the theory at fusion:

 

Hydrogen Energy for Beginners - Google Books

 

Write yourself in. Figment

 

"Decay" to a more massive particle, sounded counter intuitive to me. I would think massive energy needs to be involved, such as the fusion.

 

 

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