What is Nuclei: Definition and 141 Discussions

The raphe nuclei (Greek: ῥαφή, "seam") are a moderate-size cluster of nuclei found in the brain stem. They have 5-HT1 receptors which are coupled with Gi/Go-protein-inhibiting adenyl cyclase. They function as autoreceptors in the brain and decrease the release of serotonin. The anxiolytic drug Buspirone acts as partial agonist against these receptors. Selective serotonin reuptake inhibitor (SSRI) antidepressants are believed to act in these nuclei, as well as at their targets.

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  1. Hak

    I Impossibility of constructing a particle consisting of only neutrons and proton-neutron interaction

    Why can't we construct a particle consisting of only neutrons? Why are there nuclei of ##_2^3He## (2 protons and 1 neutron) and ##_2^4He## (2 protons and 2 neutrons) but there is no ##_2^{50}He##? Maybe a first approach might be that neutrons and protons interact with each other not through the...
  2. Astronuc

    I Nuclei in the Cosmos Symposium

    I was looking for resources on stellar nucleosynthesis, and I found the following seminar, which has been going on since 1990. The 17th Symposium will be 17-22 Sep, 2023 in Daejeon, South Korea. https://www.jinaweb.org/events/17th-international-symposium-nuclei-cosmos...
  3. amyy

    A Does 15F Qualify as an sd Shell Nucleus?

    If we call a nucleus a sd shell nucleus, should its last proton and last neutron both lie in the sd shell or just one lies in the sd shell? For example, 15F, whose proton number is 9 and neutron number is 6. Then the last proton lies in the 1d5/2 orbit and the last neutron lies in the 1p3/2...
  4. guyvsdcsniper

    Finding the distance between two nuclei right after fission

    I am trying to solve part b of this problem. I know the particles are moving at first and are at rest right after fission per the question. Using the relativistic Kinetic Energy equation and the energy between two charges I believe I can solve for r, the radius between the two charges. I am a...
  5. Mayan Fung

    A Interaction between neutrons and nuclei during scattering

    When we learn about the scattering of a particle, the context is usually a charge shooting towards a Coulomb potential. With some assumptions, we can derive the scattering cross-section pretty reasonably. Therefore, the scattering cross-section of different elements in X-ray spectroscopy is...
  6. S

    I Are some cosmic rays iron nuclei?

    I had thought that cosmic rays were all protons, but this article says sometimes it's iron. https://getpocket.com/explore/item/let-s-colonize-titan
  7. Physicsman788

    How many undecayed nuclei will remain?

    Attempt at solution: 𝑁 = 500𝑒−5 = 3.3689735 undecayed nuclei remaining Edit: Sorry guys, I found it out its 500e-0.5x5
  8. S

    Applying least squares to measurement of nuclei masses and Q-value

    Consider the problem in the attached image. The difference between A and B is 0.0020(20). How does one use the least squares method, particularly in matrix form, to find the best value of the masses of A and B respectively, as well as the Q-value? Aren't more measurements needed for the masses...
  9. S

    I Magnitude limits for active galactic nuclei

    Milky Way centre cannot be seen because of Great Rift, but it is known as a loud radio source Sagittarius A since 1930s. What would be the absolute magnitude of Sagittarius A if it could be seen? Visual magnitude? Not all galaxies have loud centres. Large Magellanic Cloud does not show a sign...
  10. M

    I Why Is Octupole Deformation Measurable in Nuclei but Not Dipole Deformation?

    Hello! I don't know much about this, so maybe the answer to my questions follows directly from the math of it, but I was wondering if there is an answer providing more physics intuition to this, not just math: Why can a nucleus have an octupole deformation, as a ground state stationary state...
  11. K

    I Quadrupole deformation in nuclei

    Hello! I am confused about the definition of the quadrupole moment in nuclei. One definition I found, in Wong, says that the quadrupole moment of a nucleus is given (ignoring some numerical constant) by: $$<J,M=J|r^2Y_{20}|J,M=J>$$ so the expectation value of a second order spherical harmonic...
  12. K

    I Low-lying excited states in nuclei

    Hello! How are the parity and spin of excited states of nuclei measured experimentally. I imagine that the energy can be easily measured by exciting the nucleus (by colliding it with a nucleon or electron for example) and then measuring the emitted photons. But how can one infer the spin and...
  13. haushofer

    I Alpha decay: why Helium nuclei?

    Dear all, in my teaching of nuclear physics at high school level I noticed that I never really wondered about why alpha decay consists of helium nuclei. So I consulted a lot of lecture notes online, but couldn't find a satisfying answer. The texts I used in the past are "concepts of modern...
  14. Zahid Iftikhar

    I Stability of Nuclei: Why Don't Nuclei Split at Thermal Energies?

    Hi I need help from PF scholars to figure out one difficulty in understanding stability of nucleus. Nuclei remain unaffected during chemical reactions taking place even at very high temperatures and pressures. But their binding energy figures are not that high. Such chemical reactions have heat...
  15. G

    NMR: Why do "identical" nuclei not couple with each other?

    Hello there, Spin–spin coupling is encountered in the majority of NMR spectra. However, it does only occur when the two interacting nuclei are non-"identical". But why is the coupling not occurring between "identical" nuclei? I have been wondering about this because I could not think of a...
  16. G

    B Strong nuclei force and extra dimensions

    Sorry for my speculative question, i just wondered, is there any sensible theory that thinks strong nuclei force is so weak in the distance, because it isn't three dimensional? Again i don't intend to say my speculations are facts, but i think the above question needs a bit explanation. I would...
  17. F

    Why do nuclei form in the first place if the protons repel each other?

    Now that I think about this some more, nucleons can get close together if they are traveling at a very high speed. So maybe when the Earth first formed, stuff was moving fast (or at high temperature/pressure) and this forced nucleons together into nuclei? I don't really know what I'm talking...
  18. Geofleur

    I The fate of neutron rich nuclei

    I've been trying to understand why adding neutrons to a nucleus will eventually destabilize it; I would like to know if the following explanation is correct: The neutron has a slightly higher mass than the proton. But higher mass translates into higher energy because ## E = mc^2 ##. However...
  19. S

    I Distribution of nucleons in the nuclei

    What does this diagram tell us about the distribution of nucleons in the nuclei? - The diagram is from Krane Introductory Nuclear Physics I know that nucleons don't congregate around a central part of a nucleus, but instead have a constant distribution throughout. i.e. The number of nucleons...
  20. S

    A Size of nuclei wave function in a crystal

    I need to know what is the typical extention of the (spatial) wavefunction of an atomic nucleus in a crystal, in particular I am interested to the case of a Germanium cristal. Please together with the actual number of the size of the nuclei wavefunctions, let me know the references (articles or...
  21. Jimtaff

    I Do we make atoms of Oganneson etc or are they nuclei?

    When the heaviest elements such as element 118 (Oganesson) are created, the production is described as a a collision of an ion projectile (eg calcium-48) with a target atom (eg californium 249). Does this collision result in an atom of oganesson before the decay to 116 (Livermorium) or is it...
  22. T

    Show that three new found nuclei are unstable

    Homework Statement Question: Three new nuclei are claimed to have been discovered: ##\left(i\right)\:^{26}_9F\:,\:\left(ii\right)\:^{63}_{32}Ge,\:\left(iii\right)^{94}_{47}Ag## For each nucleus, what about it enables you to say it must be unstable Homework EquationsThe Attempt at a Solution...
  23. Vectronix

    B Do atomic nuclei transfer momentum to electron orbitals?

    Do protons' inherent gyroscopic nature produce progressive ripples in the electromagnetic field? If so, then is there an ensemble of transverse electromagnetic undulations arising from the proton's angular momentum that contribute to electronic orbital energy in, say, a hydrogen atom? If these...
  24. J

    I Binding Energy: Exploring How Nucleons Become Heavier

    So we have a nucleus. Let's say its a helium nucleus. If I want to split this nucleus into its constituent nucleons, I must do work against the strong force which is holding it together. Now that I have done the work, the particles are no longer bound. I have done work against the strong force...
  25. T

    Nulcear fission, two daughter nuclei

    Homework Statement An unstable nucleus with mass M is in an excited state with excitation energy E* and undergoes spontaneous fission into two daughter nuclei "1" and "2" and zero fast neutrons. What will be the kinetic energy KE (in MeV) of the daughter nucleus "1"? M = 233.9493amu E* =...
  26. S

    B Explaination of beta + decay in layman language

    QUESTION: I read in book that in beta + decay proton decays to neutron But i can't understand how it is possible if proton mass is less than neutron mass.I read on net but it says 'quarks' and 'd u p' things which i don't study about currently. Also why it only happen inside nucleus?What...
  27. H Tomasz Grzybowski

    A Mechanism of α decay - truth about structure of nuclei

    α decay probably implies that heavy enough nuclei which undergo this decay, consist relatively loosely bound α particles and extra neutrons. I haven't found any theory which views nuclei in this way. I value truth in science, and would like to know it, also regarding stucture of nuclei and...
  28. D

    B Incurring hysteresis between protons in nuclei only....

    I'm curious if there is any documented effect along these lines, via EM waves. Hypothetically, all objects have a resonant frequency which will cause them to vibrate when matched. As an example, stone has a resonant frequency per type, its molecules also, atoms also, and I personally theorize...
  29. A

    A All experimental data for Super heavy nuclei

    dear physicists I need all the half life experimental data available so far, for SHNs, I mean Z=104 - 118 (T1/2) can you help me? where do I get access to this data?
  30. P

    B How do Neutrons and U235 Nuclei get out of the fuel rod

    I understand that there are fuel rods, water control rods. I also understand that fuel rods are metal tubes filled with special U235 pellets. Finally, I understand that water slows the neutrons down enough to collide. How do the neutrons and U235 nuclei get out of the metal encased fuel rod...
  31. Kevin McHugh

    I Exploring Half Lives of Pions in Nuclei

    Do they exist in nature, i.e. in high Z nuclei, or are they only created in scattering experiments? Are the half lives increased in bound states? Why do positive pions get trapped in the potential well as well as negative pions?
  32. B

    Semi-empirical mass formula: most stable isobar for odd A

    Homework Statement Using the Semi-empirical Mass Formula show that for fixed odd atomic mass number, A, the most stable isobar has a neutron to proton ratio given by N/Z = 1 + aCA2/3/(2aA) Homework Equations B(A,Z) = aV A − aS A2/3 − aCZ2A-1/3 − aA(Z − N)2/A + pairing term The Attempt at a...
  33. D

    What is the Relative Concentration of Helium at 3 Minutes After the Big Bang?

    Homework Statement the relative concentration by mass of helium at 3 minutes after the big bang is 2-5 parts per 100,000. If you had 1 kilogram of the normal matter from the universe at a time 3 minutes after the big bang, how much of it would be normal helium nuclei? Homework EquationsThe...
  34. T

    B Nuclear Decay with time (half-life,initial activity/ nuclei)

    Hi! I just keep having a hard time looking for the formula stating the relationship between half life, the initial number of unstable nuclei and the initial activity, can someone help me on that ? To be more specific, here is a problem which can be solved using that formula: "A substance has a...
  35. D

    I Confirming Nuclei Deformation: Theory & Experimental Considerations

    Literature survey on Nuclei deformation I found theoretical calculations and prediction however I could not find experimental considerations. 1. How nuclei deformation confirmed? 2. Is it possible to consider deformation modulus constant that equivalent to Yang Modulus in mechanics? Are there...
  36. looseleaf

    A Entanglement between nuclei via fission

    Hi everybody! Wasn't sure whether to post this here or in Quantum Mechanics, decided I would start here. I was wondering how the entanglement structure between the nucleons of two nuclei would evolve during a fission event. Correct me if I'm wrong but wouldn't the two sets of nucleons...
  37. P

    I Shell Model: Filling Up Nuclei

    I'm a bit confused about how things fill up in the shell model. Here is my understanding: the potential we are working with is the net potential due to the other nucleons that a proton or neutron feels throughout the nucleus; it is a combination of a square and harmonic oscillator potential...
  38. Garlic

    Electron capture in fully ionised nuclei

    Hello everyone, What happens if an isotope that normally decays through EC has no electrons at all? For example how does 7Be4+ decay?
  39. X

    Elastic collision between alpha particle and gold Nuclei

    Homework Statement When an alpha particle collides elastically with a nucleus, the nucleus recoils. Suppose a 3.94 MeV alpha particle has a head-on elastic collision with a gold nucleus that is initially at rest. What is the kinetic energy of (a) the recoiling nucleus and (b) the rebounding...
  40. A

    Large nuclei to proton ratios reduce repulsion in a nucleus

    Hi, I am new here. I am just reading over my notes for stable and unstable nuclei and I came across this sentence: 'Large nuclei require a higher neutron proton ratio as this adds more nuclear attraction without adding repulsion'. I was wondering why the large ratio would reduce repulsion? Thank...
  41. jlefevre76

    Simulating Heavy Nuclei Reactions with Software: A Beginner's Guide

    Hey, is there software out there capable of simulating heavy nuclei? For instance, U235 or other fissile materials? When I say simulating, I mean using all the appropriate equations (nuclear strong force fields represented, Schrodinger equations represented, etc). Mainly, I would want one that...
  42. avito009

    Popular misconception -- When the deuterium nuclei fuses to form a helium nucleus

    I am no Einstein but I would like to expand my knowledge and share it. When two deuterium atoms fuse together they become a helium nuclei. Now deuterium nuclei contains 1 proton and 1 neutron. When the deuterium nuclei fuses to form a helium nuclei. Helium nuclei contains 2 protons, and 2...
  43. P

    Electron capture and heavy nuclei

    Hi, is it true that the heavy atoms decaying only by electron capture should have globally a half-life shorter than ligher nuclei (decaying also only by electron capture)? This assumption comes from the fact heavy atoms have inner electron "closer" to their nucleus than the lighter ones and so a...
  44. S

    Proton–lithium-7 fusion - energy of the two He nuclei?

    In articles on aneutronic fusion, the reaction Proton–lithium-7 is mentioned as a possibility. Now I wonder; what is the kinetic energy of the 2 He nuclei? How much is gamma rays? Proton–lithium-7 fusion p + 7Li → 4He + 4He + 17.2 MeV
  45. Albo1125

    Using the derivative of the formula of the number of nuclei

    Hi all, I have a question concerning the derivative of the formula of the number of nuclei. I hope I've posted this in the right section, I'm new here :P. Anyway, in the question, the given values are: At a certain time t, there is an amount of radioactive Br-82. The activity A is 7.4*1014 Bq...
  46. M

    Elastic scattering of WIMPs off nuclei

    Hello, My problem is as follows I've tried differentiating to find the maximum and I've tried plotting E against m_{\chi} for a range of values and this did not suggest a maximum at m_N = m_{\chi}. Could someone explain why it is the case that the energy transfer is maximum when these masses...
  47. A

    Stability in Nuclei: How Mass Energy Helps

    How does the nucleons losing some of its mass energy help in making it more stable?
  48. gennarakis

    Find the mass number A of the most stable nuclei given Z

    Homework Statement Knowing the Z (number of protons) of an element, how can I find N (number of neutrons) or A (mass number) of the element? Homework Equations I tried to use the semi-empirical mass formula EB = ανΑ - αsA2/3 - αcZ2/A1/3 - αΑ(Α-2Ζ)2/Α - δ(Α,Ζ) for this. The Attempt at a...
  49. M

    Different values of g factor (gyromagnetic ratio) of nuclei

    Hi, last week I read Rabi's paper "The Molcular Beam Resonance Method". This paper contains the basic idea of the oscillation which we call "Rabi Oscillation" as many of you guys know. However, at the end of this paper, Rabi calculates nuclear magnetic moments of Li (atomic mass 6), Li (atomic...