What is Beta decay: Definition and 147 Discussions

In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta particle (fast energetic electron or positron) is emitted from an atomic nucleus, transforming the original nuclide to an isobar of that nuclide. For example, beta decay of a neutron transforms it into a proton by the emission of an electron accompanied by an antineutrino; or, conversely a proton is converted into a neutron by the emission of a positron with a neutrino in so-called positron emission. Neither the beta particle nor its associated (anti-)neutrino exist within the nucleus prior to beta decay, but are created in the decay process. By this process, unstable atoms obtain a more stable ratio of protons to neutrons. The probability of a nuclide decaying due to beta and other forms of decay is determined by its nuclear binding energy. The binding energies of all existing nuclides form what is called the nuclear band or valley of stability. For either electron or positron emission to be energetically possible, the energy release (see below) or Q value must be positive.
Beta decay is a consequence of the weak force, which is characterized by relatively lengthy decay times. Nucleons are composed of up quarks and down quarks, and the weak force allows a quark to change its flavour by emission of a W boson leading to creation of an electron/antineutrino or positron/neutrino pair. For example, a neutron, composed of two down quarks and an up quark, decays to a proton composed of a down quark and two up quarks.
Electron capture is sometimes included as a type of beta decay, because the basic nuclear process, mediated by the weak force, is the same. In electron capture, an inner atomic electron is captured by a proton in the nucleus, transforming it into a neutron, and an electron neutrino is released.

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  1. E

    Inverse Beta Decay: Why is it Forbidden for a Free Proton?

    Homework Statement Why is the inverse Beta decay forbidden for a free proton? Homework Equations p -> n + e(+)(positron) + v (neutrino) The Attempt at a Solution Is it because, the change in the Q value must be the same for each decay?
  2. J

    Quick question about positive beta decay and mass defect?

    Hi, I was wondering about something in my notes that I don't quite understand. In positive beta decay in nuclear physics, we have a proton becoming a neutron and kicking out a positron and an electron neutrino (which is assumed massless here). In the expression for the energy released, Q =...
  3. R

    Beta Decay Experiment: Investigating Maximum Energy

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  4. C

    Understanding Neutron Beta Decay: The Role of W Boson and Energies Involved

    Most accepted theories make sense, but the energies involved in the beta decay of a neutron into a proton confuses me. How can a down quark change into an up quark by emiting an electron and an anti electron neutrino via a w boson, the figures don't add up! Using the figures of mass it goes...
  5. B

    Why is the equation for beta decay written as e- = 0 and what does it mean?

    I was reading a text, describing the following disintegration: ^{234}_{90}Th\xrightarrow{}~^{0}_{-1}e+~^{234}_{91}Pa However, I prefer to understand it as, ^{234}_{90}Th\xrightarrow{}~e^{-}+~^{234}_{91}Pa Of course, the above two equations are missing out the antineutrino. Could someone...
  6. B

    Beta Decay of 32 Phosphorus - Is It Positively Charged?

    Hi all, when an atom goes through a beta decay, say 32 phosphorus. The final state is then 16 protons, 16 neutrons, and 15 electrons. This seems to be an ion of sulfur. My question is, does the atom remain in a positively charged state? or does it ionize it suuroundings and captures an...
  7. T

    Calculating energy released from beta decay

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  8. S

    Beta decay fundamental question

    Can someone please clarify beta decay for me. As I understand it, in B- decay, a neutron turns into a proton, electron, and anti-neutrino, then the electron and anti-neutrino are ejected. But from this example, it looks like there are two additional electrons as a result of decay. 19/8 O ->...
  9. A

    Beta Decay: Experimental Demonstration & Critique

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  10. M

    Is the Beta Decay Mass Condition Dependent on Atomic Masses?

    In beta decay, positron emission, how come the condition for decay is: M_p > M_d + 2m_e Thats: atomic mass of parent > "daughter + twice the mass of an electron. I'm sure there is some simple way of showing it, but I can't seem to find it! Also, is the most stable isobar on an atomic...
  11. E

    Beta Decay not a specific problem, just a question

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  12. A

    The antineutrino in Beta decay

    I understand the physical changes in beta decay that eventually lead to the virtual particle, a W- boson being formed. However I do not understand the physical changes that take place, which eventually lead to an antineutrino being emitted. What changes take place in the W- boson, that make it...
  13. matt_crouch

    Beta Decay & Quarks - A-Level Physics Explained

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  14. liometopum

    Beta Decay Neutron: Proton, Electron Mass Difference

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  15. J

    Boson and electron mass and speed in beta decay

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  16. A

    The antineutrino in beta decay.

    Hello fellow physicists and mathematicians! I am 15 years of age and trying to understand beta decay. At present I understand how the proton turns into a neutron etc... The problem is I do not understand how the decay of a W- boson turns into an antineutrino. I've read that the W- boson has...
  17. V

    Another question about beta decay (stupid ones)

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  18. V

    Beta Decay: Why Isomeric State Has Long Half-Life

    Please look at the attached file. The first part of the question: why it doesn't decay to the GS. I think that's simply because the nuclear spin changes by 4 and therefore this decay is very supressed. But how "is it possible for the isomeric state at 140kev which decays by gamma emisson, to...
  19. N

    Beta Decay Problem: Solve KE of Recoil Nucleus

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  20. B

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    Can anybody explain me the conditions for become a beta decay. for example : Md (Z=101,A=255) --> No (Z=102,A=255) + e (electron) + -Ve (anti-notrino) can this nuclear reaction be?
  21. J

    Beta Decay, how can baryons produce Leptons ?

    Hey I know : n = p+ + e- + (Ve) meaning that : p+ = n - e- - (Ve) = n + e+ + Ve ?? But, how does a Baryon like a proton or a neutron produce leptons ? and how this change can occur : n = p+ + e- + (Ve) u d d = u u d + e- + (Ve) How can a down quark become a Up...
  22. A

    Lepton beta decay when m near m_W?

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  23. S

    Double Beta Decay: Questions from a Newbie

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  24. D

    Beta Decay Curve: KE Not Constant?

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  25. Y

    How Does a Down Quark Transform Into an Up Quark During Beta Decay?

    for beta decay n --> p + e- + antineutrino since neutron has quarks udd while proton has uud, only the d changes to u. is it correct to guess that it is the down quark inside the neutron which "transform" into up quark? ie d --> u + e- + antineutrino
  26. A

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  27. R

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  28. D

    Unbelievable Half-Life of Zn-64: Investigating Cu-64 Beta Decay

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  29. P

    Beta Decay: Puzzling Creation of Antimatter

    In beta decay, an antibuetrino or an positron is emitted from the nucleus. how is this possible? how can antimatter come directly from matter? This is pizzling...:confused:
  30. T

    Beta decay and electron capture.

    Recently the radation physics class I am taking reviewed decay and I wondered how beta minus decay and electron capture can both emit neutrinos. I tried asking my professor, but I do not think I explained my question well enough to him. To explain my mindset, imagine you have only one...
  31. Q

    Beta Decay Proton: Ion Formation?

    if beta decay is the result of ejection of electron from the decay of a neutron into a proton and electron does that mean the the resultant product nucleus would be an ion since it would hav an extra proton? and same thing when a positron is formed from decay of proton?
  32. C

    Software for calculating beta decay

    Does anyone have a link or pointer to preferably freely available software with which I can calculate the energy spectrum of the electrons or positrons liberated in regular beta or beta+ - decay for a given isotope? My background is not in physics (chemical engineering, rather), and although I...
  33. P

    What Causes Beta Decay to Be More Common in Heavy Elements?

    Hey i was just wondering if anyone could help me out and shed some light into " why is B^- decay (emission of an electron) far more common among the heavy elements than the B^+ (emission of a positron) or electron capture decays?" I am looking at a plot of Z vs. N for various nuclei and believe...
  34. R

    I have a question about Beta Decay

    In Beta radioactive decay, how do quarks rearrange themselves in these situations? Do they do this? ß+ : 1p (2u, 1d) + energy ==> 1n (2d, 1u) + 1e- ß- : 1n (2d, 1u) ==> 1p (2u, 1d) + 1e- + energy I believe I have these right. Positive Beta decay is "endothermic" while negative...
  35. E

    Neutrino detection by inverse beta decay

    Hi, I have the following question: Neutrinos can be detected by an inverse beta-decay. The probability for an interaction of a neutrino and a proton is 10^(-43). How large should be a detector filled with water in order to let interact one of 1 million neutrinos with a proton? What would be...
  36. E

    Beta decay - derive an expression relating source angle to energy

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  37. X

    Atomic Number Change in Fermium-252 After Beta Decay

    Suppose that the fermium-252 nucleus could undergo a decay in which a (beta-) particle was produced. How would this affect the atomic number of the nucleus? Explain briefly. This looks pretty easy, but I think it's trying to trick you. Thank you for helping.
  38. S

    Beta Decay Questions: Help Understanding Angular Momentum

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  39. S

    Understanding Beta Decay: How It Affects Atoms and Ionization

    When an atom experience beta decay, will the atom become ion? This is my deduction: 1.An atom will release an electron in beta decay. 2.The electron is replaced by the electon produced from the decay of neutron. 3.However, the proton number increase by one. It still need one more electron...
  40. T

    Leptons produced during beta decay

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  41. M

    Beta Decay & Charge: Exploring the Nuclide

    Okay, so one of my hall mates across the way asked this question about his Chemistry, and then I realized that I wasn't too sure why it was myself, so I figured I'd pass this on to you. Take the decay equation {}^{24}_{11}Na \rightarrow {}^{24}_{12}Mg + {}^0_{-1}\beta His question...
  42. M

    Solving the Charge Conundrum in Negative Beta Decay

    There's a question which bugged me for quite a while. Say, in negative beta decay, in a tritium nucleus. 2 neutrons, 1 proton, 1 orbital electron. The neutron changes into a proton, by the exchanging of a W- particle which soon decays into a electron and an antineutrino. charge is conserved...
  43. R

    How do W particles and beta decay relate to muons?

    w particle and beta decay and muons How many w particles,at any instant in time, are there in one cubic metre of a mass of radioactive nuclei which undergo beta decay? And how fast do these w particles move on average? How many w particles are,at any instant in time, in the neighbourhood of...
  44. J

    Why is beta decay suppressed in a free neutron?

    A free neutron is said to have a half life of something around 15 minutes, or maybe it's 18 minutes, I can't remember exactly. This brings up a couple of questions. (1) How does the experimenter maintain a neutron in a free state? Presumably maintaining a high vacuum is one requirement, but...
  45. J

    What is the W- boson in beta decay?

    neutron => proton + W- => proton + electron + electron anti-neutrino What're the quarks composing W-? To convert a neutron to a proton, there would need to be the expulsion of a down anti-up pair. That would mean a tad bit of mass loss, how does this work?
  46. R

    Beta Decay of Strontium: Yttrium Ionisation?

    During beta decay (eg of strontium) a neutron becomes a proton and an electron. The electron then leaves the atom. The atom (yttrium) must then have one more proton than electron so does beta decay of strontium always leave IONISED yttrium?
  47. R

    Calculating Kinetic Energy & Speed of a Particle in Beta Decay Reaction

    How do i calulate the kinetic energy and speed of a particle released form a beta decay reaction? for example, if i have Na -> Mg + e (i can't type in the atomic masses and numbers) Would i subtract the mass of Mg from Na ? m=m_Na-m_Mg =23.990961u-23.985042 =0.005937u then multiply...
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