Creating Excited States of Nuclei Without Neutrons: Is it Possible?

In summary, the conversation discusses the possibility of creating excited states of a nucleus without using neutrons. The use of microwaves and magnetic fields to excite nuclei is mentioned, as well as the Zeeman effect and Mossbauer spectrum. The existence of nuclear isomers with small energy gaps is also discussed, with some examples such as Th-229m and U236. It is suggested that these states could potentially be populated using a laser, but not with a microwave due to the large difference in energy.
  • #1
x_engineer
55
8
Can one go about creating excited states of a nucleus without using neutrons?

For example, Aluminium 26 exists in a ground state that has a half-life of about 70000 years, and decays by beta particle emission. It can also exist in an excited state that decays with a half-life of about 6.3 seconds (Wikipedia). Unfortunately this emits a positron with the decay, or captures an electron. Is there a beta emitter with these characterisitics?
 
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  • #2
If you can get a gamma of the exact right energy to excite the nucleus to the state you want you should be able to hit it with that.
 
  • #3
Actually I was wondering if there was a mechanism to excite it without using something like that. I know that microwave radiation can pump energy into a nucleus under some circumstances (e.g. when the energy levels are broadened into bands under the influence of a magnetic field)

I guess the real question is how strong a magnetic field do you need to broaden an energy level to the point where the ground state levels are connected by a ladder of much smaller steps.

Gamma rays are too uncontrollable to be efficient in small systems. So are neutrons. Protons and electrons are tough to use but preferable because you can constrain uncertainty along some dimensions by trading off against other dimensions.
 
  • #4
NO, you cannot excite a nucleus with microwaves! The energy of microwaves is many magnitudes too small. Are you seriously wanting to create a nuclear isomer in your kitchen??

Isomers are not produced by exciting the ground state, they're produced in the same reaction that originally made the nuclide, ground state and excited state both being produced at the same time.
 
  • #5
You can create an excited state of a nucleus with microwaves and magnetic fields - that is what NMR technology is about. Of course the excitation is tiny and does not fundamentally change the nucleus, and is just reemitted a little later.

The Zeeman effect splits electronic states of an atom. If you put the atoms in a lattice (even without a magnetic field!), the electronic levels broaden and form a band instead of a sharp line. I was wondering if there was a similar mechanism with nucleii.

If you look at http://atom.kaeri.re.kr/ton/nuc12.html and check out U236 you see a metastable state at "0.000MeV" which has a half-life of 121ns compared to the ground state with a half-life of 23420000 years, and both disintegrate via spontaneous fission. Since they use three decimal places I assume the separation between those states is under 500eV. It is an even-even nucleus so magnetism is not going to work to bridge the gap. But a 500eV X-ray might. How small is the gap actually?

Np237 is similar, but the first excited state is at 2.8MeV. I found some others with differences as little as 75keV. Al26 has a gap of 228keV. Interestingly, there are some where the excited state has a longer half-life than the ground state!

The ones that decay by IT back to the ground state are uninteresting (to me at least).
 
  • #6
NMR is totally different, that is just about the energy difference between nuclei whose magnetic dipole moment is aligned with the magnetic field and those which aren't. I.e. the nucleus is just rotated in space. It isn't an "excited state" of the nucleus.

There IS a nuclear Zeeman effect, it is associated with the Mossbauer effect, but the shifts in the energy levels of the nucleus are very small. Check out this Mossbauer spectrum for Fe-57, the splitting is of the order of 10^-7 eV: http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/ironze.html.

Hmm, ok so it seems there are some low energy nuclear transitions based on this effect. Check out http://en.wikipedia.org/wiki/Isotopes_of_thorium, it talks of a nuclear isomer with an excitation energy of ~7.6 eV. Looking at the reference for this measurement they say it is due to the energy splitting of the ground state doublet. Pretty cool.
 
  • #7
I wasn't aware of this unique state, Th-229m, which apparently has a remarkably low excitation energy of 7.6 eV. But even this is still in the ultraviolet range, shorter than visible light. The Wikipedia article suggests it might prove possible to populate the state by means of a laser.

You're thinking of doing this with a microwave? An energy of 7.6 eV corresponds to a wavelength of about 160 nm, whereas commercial microwave ovens operate at 2.45 GHz, with a wavelength of 122 mm, six orders of magnitude lower.
 

1. Can excited states of nuclei be created without the presence of neutrons?

Yes, it is possible to create excited states of nuclei without neutrons. This can be achieved through various methods such as bombarding the nuclei with high energy particles or through nuclear reactions.

2. What are the advantages of creating excited states of nuclei without neutrons?

Creating excited states of nuclei without neutrons can provide valuable insights into the fundamental properties of nuclei and their interactions. It can also help in the development of new technologies and applications in fields such as medicine and energy production.

3. Are there any challenges in creating excited states of nuclei without neutrons?

Yes, there are several challenges in creating excited states of nuclei without neutrons. These include the need for high energy and precise control in the nuclear reactions, as well as the difficulty in isolating and detecting these excited states.

4. How is the stability of the excited states of nuclei without neutrons determined?

The stability of excited states of nuclei without neutrons is determined by their half-lives, which is the amount of time it takes for half of the excited nuclei to decay into a more stable state. Shorter half-lives indicate less stable excited states.

5. What are the potential applications of creating excited states of nuclei without neutrons?

The creation of excited states of nuclei without neutrons has potential applications in fields such as nuclear medicine, where these excited states can be used in imaging and therapy, as well as in nuclear energy production and nuclear waste management.

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