What is Nuclear decay: Definition and 72 Discussions

Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is considered radioactive. Three of the most common types of decay are alpha decay (𝛼-decay), beta decay (𝛽-decay), and gamma decay (𝛾-decay), all of which involve emitting one or more particles or photons. The weak force is the mechanism that is responsible for beta decay, while the other two are governed by the usual electromagnetic and strong forces.Radioactive decay is a stochastic (i.e. random) process at the level of single atoms. According to quantum theory, it is impossible to predict when a particular atom will decay, regardless of how long the atom has existed. However, for a significant number of identical atoms, the overall decay rate can be expressed as a decay constant or as half-life. The half-lives of radioactive atoms have a huge range; from nearly instantaneous to far longer than the age of the universe.
The decaying nucleus is called the parent radionuclide (or parent radioisotope), and the process produces at least one daughter nuclide. Except for gamma decay or internal conversion from a nuclear excited state, the decay is a nuclear transmutation resulting in a daughter containing a different number of protons or neutrons (or both). When the number of protons changes, an atom of a different chemical element is created.

Alpha decay occurs when the nucleus ejects an alpha particle (helium nucleus).
Beta decay occurs in two ways;
(i) beta-minus decay, when the nucleus emits an electron and an antineutrino in a process that changes a neutron to a proton.
(ii) beta-plus decay, when the nucleus emits a positron and a neutrino in a process that changes a proton to a neutron, also known as positron emission.
In gamma decay a radioactive nucleus first decays by the emission of an alpha or beta particle. The daughter nucleus that results is usually left in an excited state and it can decay to a lower energy state by emitting a gamma ray photon.
In neutron emission, extremely neutron-rich nuclei, formed due to other types of decay or after many successive neutron captures, occasionally lose energy by way of neutron emission, resulting in a change from one isotope to another of the same element.
In electron capture, the nucleus may capture an orbiting electron, causing a proton to convert into a neutron in a process called electron capture. A neutrino and a gamma ray are subsequently emitted.
In cluster decay and nuclear fission, a nucleus heavier than an alpha particle is emitted.By contrast, there are radioactive decay processes that do not result in a nuclear transmutation. The energy of an excited nucleus may be emitted as a gamma ray in a process called gamma decay, or that energy may be lost when the nucleus interacts with an orbital electron causing its ejection from the atom, in a process called internal conversion. Another type of radioactive decay results in products that vary, appearing as two or more "fragments" of the original nucleus with a range of possible masses. This decay, called spontaneous fission, happens when a large unstable nucleus spontaneously splits into two (or occasionally three) smaller daughter nuclei, and generally leads to the emission of gamma rays, neutrons, or other particles from those products.
In contrast, decay products from a nucleus with spin may be distributed non-isotropically with respect to that spin direction. Either because of an external influence such as an electromagnetic field, or because the nucleus was produced in a dynamic process that constrained the direction of its spin, the anisotropy may be detectable. Such a parent process could be a previous decay, or a nuclear reaction.For a summary table showing the number of stable and radioactive nuclides in each category, see radionuclide. There are 28 naturally occurring chemical elements on Earth that are radioactive, consisting of 34 radionuclides (6 elements have 2 different radionuclides) that date before the time of formation of the Solar System. These 34 are known as primordial nuclides. Well-known examples are uranium and thorium, but also included are naturally occurring long-lived radioisotopes, such as potassium-40.
Another 50 or so shorter-lived radionuclides, such as radium-226 and radon-222, found on Earth, are the products of decay chains that began with the primordial nuclides, or are the product of ongoing cosmogenic processes, such as the production of carbon-14 from nitrogen-14 in the atmosphere by cosmic rays. Radionuclides may also be produced artificially in particle accelerators or nuclear reactors, resulting in 650 of these with half-lives of over an hour, and several thousand more with even shorter half-lives. (See List of nuclides for a list of these sorted by half-life.)

View More On Wikipedia.org
  1. M

    A Pandora's Box: Carbon-14 vicious cycle from transmutation

    Hello Physics community I know this comes off as pseudoscience but think about it for a second. Couple years a ago a colleague explained during a conversation how a neutron source wich emmits certain fast and slow neutrons could cause a transmutation vicious cycle in Atmospheric conditions that...
  2. M

    B Increase in radiation from radium pocket watch hands

    Hello, I'm new here and recently did a little experiment in my free time that left me puzzled. To sum it up I ran 2 tests, each running over 12 hours long, they where focused on 3 radium pocket watch hands that I bought off of eBay a while ago and a small piece of beryllium. These hands are...
  3. R

    Show that the minimum in alpha-decay spectrum is caused by interference of peak

    This problem set considers (beta-delayed) alpha decay of ##{}^{20}Na##. I'm currently stuck in the following exercise and was hoping some of you could help me in the right way. Thanks in advance! The problem is: c) The experimental spectrum of ##{}^{20}Na## can be found below. Apart from peaks...
  4. Graham87

    Troubleshooting nuclear decay, electron binding energies, internal contributions

    How do you know which binding energy shell to use? In the solution it uses K and L2. Why specifically L2 and not L3 or L1 for example? And what should I do with the information to omit electrons lower than 20kev? I initially thought that meant to omit the electron binding energies lower than...
  5. Graham87

    Troubleshooting Nuclear Reactions: Decay, Gamma Rays & More

    The problem comes with solutions. However, I dont get the 3 steps in the solutions. Why do they calculate decay for 120min in step 3? And why is only the daughter nuclide relevant and no granddaughter? There might be something lacking in my knowledge about nuclear reactions. Also, I don't know...
  6. Admiralibr123

    I Algorithmic model for primary decay chains

    I have seen "radioactivedecay.py" python library which employs measured experimental data for its calculations. I have seen models that solve the system of differential equation with numerical algorithms to predict the proportion of nuclides at any given time. But I have yet to see a...
  7. B

    Nuclear Decay Scheme: Learn the Basics

    I'm not too sure where to start, do I differentiate the equation?
  8. F

    B In a nuclear decay, is all of the released energy kinetic energy?

    I'm trying to make up an example for my students to illustrate that in nuclear decay, mass-energy and momentum are both conserved. I found this problem: https://physics.stackexchange.com/questions/304277/calculate-velocity-of-radon-220-nuclear-after-decay I am trying to modify it so that they...
  9. A

    A "Reversal" of Nuclear Decay in Beta Emitters

    Hello all, I've got a question on nuclear decay "reversal" in beta emitters. I've been researching the Cowan-Reines experiment, which used neutrinos to convert protons into neutrons. Recently, I found out that the particle which hits the proton need not necessarily be a neutrino in order to...
  10. cahill

    I Change in chemical potential energy from nuclear decay

    I have been amateur reading about beta decay. The example given for electron capture was krypton-81 into bromine-81. Going from a noble gas to a halogen gives rise to a big change in chemical potential energy. How is this energy accounted for in the equations of the reactant particles and...
  11. A

    A Quantum Anti-Zeno Effect and Decay Rates

    Hey everyone, I have a question about how "viable" the Quantum Anti-Zeno Effect (AZE) is at lowering decay rates in radioactive nuclei. We know that the AZE can, in fact, reduce the half life of radioactive isotopes, but there seems to be a barrier to that. AZE states that decay can be...
  12. cmyers152

    What Ground-State Beta Decays Are Possible for Isobaric Mass Chain A=141?

    Homework Statement Consider the isobaric mass chain A=141. Using the NNDC website, determine what types of ground-state beta decays are possible for different elements within this chain (beta minus, beta plus, EC, etc.) as well as the nature (allowed, first-forbidden, etc.) Homework Equations...
  13. B

    Find the change in mass from the KE (nuclear decay)

    Homework Statement A nucleus A decays into two nuclei B and C. The two nuclei have a combined kinetic energy of 581.9 MeV. What is the difference between the rest mass of the parent nucleus A and the combined rest mass of the two produced nuclei? Give your answer in atomic mass units u, with...
  14. tinocasals

    Nuclear physics interesting experiments and activities

    Hi there, I'm looking for some interesting activities regarding nuclear physics in high school. I already have: - building a cloud chamber with dry ice or peltier modules - simulating radioactive decay with dice - simulating Rutherford's experiment hitting with glass marbles a hidden target...
  15. A

    I End Point Energy and Q value in beta decay

    I know that Q value of a reaction is the difference between total initial mass-energy and total final mass-energy of all the products. Then shouldn't be this also the maximum kinetic energy and hence endpoint energy of an electron in beta decay. But what I have read endpoint energy ##E_0 = Q +...
  16. R

    Decay Processes of 39Ca, 39Ar, and 40K

    Could I please check if my answers to the following three questions are correct? My answers are in bold. 1. How would you expect 39Ca to decay? a) β+ or electron capture (EC) b) Electron capture only c) β- d) α 2. How would you expect 39Ar to decay? a) β+ or electron capture (EC) b) Electron...
  17. N

    B Do temperature and gravity affect particle or nuclear decay?

    I thought of another question(s) :) does temperature affect the rate of the decay at all? Does temperature effect the energy of the decay; in that the energy of the electron anti neutrino would be higher?
  18. T

    I Is nuclear decay probability always constant?

    I have heard that the probability of an unstable nucleus decaying is always constant. Is there any way to change this probability?
  19. S

    Fukushima Is it safe to live 100 km from Fukushima for short time?

    I would like to know if is safe to stay in Sendai (less than 100 km from Fukushima). I have read different information in internet but I think is better to ask a expert, I am not sure about the radiation since it seems is not stable, it could be between 0.4-0.6 msv if I understood, is that ok to...
  20. F

    Half life - Calculate the length of time

    Homework Statement A source having a half life of 5.27 years is calibrated and found to have an activity of 3.5*10^5 Bq.The uncertainty in the calibration is +- 2% Calculate the length of time in days after the calibration has been made for the stated activity to have a maximum possible error...
  21. ORF

    I In a nuclear decay, where the dM energy goes?

    Hello Let's suppose a beta-decay. The mother nucleus is dM heavier than the daughter nucleus. What happen if the excitation energy does not match any combination of excited states in the daughter nucleus? Example: the daughter nucleus has 100keV of excitation energy, but the first exited...
  22. G

    A Nuclear Stability Calculations

    Are there equations that detail the stability of nuclei against beta decay? On a related point, I'm familiar with the chart that shows all the isotopes and their half-lives (with a good chunk undergoing beta decay), but I was wondering if that can be derived from first principles, just using the...
  23. Recycler

    I Can Nuclear Decay Be Controlled?

    Is it theoretically possible to stimulate a radioactive nucleus so that it decays on demand instead of randomly?Could this be used to accelerate decay of dangerous fission by-products?
  24. 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...
  25. C

    How do I determine if a certain nuclear decay is allowed?

    Hi, I am struggling with a question where they want me to determine whether or not three different decay are allowed. From what I have understood all decays must follow a set of conservation law. These laws are: 1 Conservation of Baryon number 2 Conservation of Lepton number 3 Conservation of...
  26. Gwyndolin

    How to derive formula for nucleus decay using this equation?

    Homework Statement The formula being derived is N=No*e^k*t, from the equation Nn=No/2^n where No is the initial number of particles and the lowercase n in the second equation is the number of half lives. The n in Nn just indicates the number of particles after so many half lives. You might also...
  27. ORF

    Nuclear decay of small amount and by different processes

    Hello I was reading this post, https://www.physicsforums.com/threads/nuclear-decay-of-a-small-number-of-atoms-calculation.853664/ and I wander if the binomial distribution is still a good model if you have a small amount of nuclei, and in addition they can decay by different processes (each...
  28. K

    Conservation of momentum and nuclear decay (Gr 12 Physics)

    Homework Statement A stationary nucleus undergoes radioactive decay. A beta particle and a neutrino are detected leaving the nucleus. What is the recoil velocity of the remaining nucleus? If the recoil velocity measured is significantly different from the calculated velocity, what conclusion...
  29. resurgance2001

    Nuclear decay of a small number of atoms calculation

    I came across a rather dubious question that a teacher had put in a power point. It said something like,"Given a sample of 100 atoms of isotope x, after one half life of the said isotope, how many atoms of the original isotope will be left?" My answer was that it was a trick question because...
  30. InsaneScientist

    Time taken for amount of a nuclear material to remain

    Homework Statement The half life T½ of Carbon-14 is 5730 years. What is its decay constant? After what length of time will 35% of an initial sample of Carbon-14 remain? Homework Equations Decay constant λ= 0.693 / T½ Where N = amount of radioactive substance, N=N0e-λt The Attempt at a...
  31. J

    What is the weight of a radioactive sample with a given half-life and activity?

    Homework Statement If a radioactive sample of 59Fe (t1/2= 44.496 d) has an activity of 1000 disintegrations per minute, what weight of 59Fe is present? Homework Equations
  32. M

    Help! Troubleshooting Nuclear Decay Equations

    I'm sorry for posting this another thread, but I accidentally posted under to wrong forum initially and could not figure out how to delete it :-(1. Homework Statement Find the missing isotope: Iodine-127 (n, alpha) My answer is Sb- 122 but it was wrong. Also, how would I go about finding the...
  33. 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...
  34. U

    Nuclear Decay - Semi Empirical Formula

    Homework Statement (a) What processes changes atomic number by 1? What are the favourable conditions? How do you tell a neutrino is involved? How can we use this to understand the mass of this particle? (b) Use semi empirical mass formula to explain why odd-odd isobars are unlikely, while...
  35. Evanish

    NASA An idea for a Pu-238 replacement for NASA space missions

    So I was reading this article about http://www.wired.com/2013/09/plutonium-238-problem/all/ and it got me thinking about possible substitutes. This is what I came up with. You make thin sheets of beryllium mixed with some kind of alpha particle emitter. You also make thin sheets of some...
  36. U

    Quark Scattering and Quark Flow Diagrams

    Homework Statement (a) Find energy of incoming beam that creates highest cross section (b) What are the differences in the two reactions, using quark diagrams? (c) What would the peaks of the two reactions be like? Homework EquationsThe Attempt at a Solution Part(a) [/B] Cross section is...
  37. U

    Quick question on Fermi Golden Rule

    Adopted from my lecture notes, found it a little fishy: Shouldn't ##\frac{dp}{dE} = \frac{E}{p}## given that ##p = \sqrt{E^2 - m^2}##. Then the relation should be instead: \frac{dp}{dE} = \frac{E}{p} = \frac{E}{\sqrt{E^2 - m^2}}
  38. U

    Fermi Golden Rule - Beta Decay

    We consider the following beta decay: ^A_ZX \rightarrow ^A_{Z+1} Y + e^{-} + \nu_e The Fermi golden rule is given by: \Gamma = \frac{2\pi}{\hbar} |A_{fi}|^2 \frac{dN}{dE_f} Reaction amplitude is given by ##A_{fi} = G_F M_{nucl} ## while density of states is given by ##dN = \frac{4 \pi...
  39. P

    Age of Sample: U-235 & U-238 Abundances

    Homework Statement The isostopc abundances of a sample is U-235 and U-238 are 0.72 and 99.27 respectively; what is the age of the sample? (assume isotope abundance was equal when sample was formed) Homework Equations \lambda=\frac{ln2}{ t_{\frac{1}{2}}} The Attempt at a Solution for U-238...
  40. P

    Can Tritium Undergo Nuclear Decay in 1 Second or 1 Eon?

    For example tritium has a half life of of 12.3 years. So if you had 2 atoms of tritium then after 12.3 year you would expect to have 1 atom of tritium and 1 atom of h-3. My question is, is it possible that tritium could decay in 1 second? Or how about 1 eon? I know its not probable but is it...
  41. V

    Nuclear decay of a mixture of P and S. (2009 USAPhO Question A2)

    The answer is not provided by AAPT. Homework Statement A mixture of ^{32}P and ^{35}S (two beta emitters widely used in biochemical research) is placed next to a detector and allowed to decay, resulting in the data (attached) below. The detector has equal sensitivity to the beta particles...
  42. J

    How Many Bananas to Power a Light Bulb?

    Homework Statement If all of the energy from decay of the 40-K in one banana could be captured and converted into electrical energy, how many bananas would be needed to power a 100 W light bulb? There is 358 mg potassium-K per 100 grams of banana half life of potassium-40 is...
  43. O

    Electrons causing nuclear decay

    Hello everybody, I am a first year and I have one more question. To what degree do electron contribute to nuclear decay? (Do electron which can 'spend' some time in the nucleus cause bigger decay?) Thanks in advance :)
  44. S

    Nuclear decay activity - value for money?

    Homework Statement Radioactive nuclei A are produced at a rate R per second in a nuclear reactor. They decay with probability λ per second. (Qu 1-2 involving deriving the rate of change and number particles at any given time, I've done this). 3) Show the activity tends to R, a constant, as...
  45. S

    Nuclear Decay: Exploring the Forces Behind it

    Hello, Would all radioactive decay lead to a daughter nuclide in a "nuclear excited" state, and if so, would this indicate that gamma rays are emitted in order for the nuclear ground/stable state to be reached after any decay? Also, if nuclear decay occurs b/c of the imbalance of...
  46. B

    Nuclear Decay question without knowing N0 or N ?

    Nuclear Decay question without knowing N0 or N ?? Homework Statement Ok so what I have an Am sample which emits alpha particles at a rate of 70Bq in 1997 and asks for the activity 8 years later (the half life of Am being 432.2 years) I found this to be 69.108 Bq, first of all does this sound...
  47. H

    Nuclear decay emission: deterministic modeling?

    Is it possible, in theory, that a radioisotope undergoing nuclear decay (eg. alpha particle emission) can be modeled so as to determine the origin and/or direction of the emitted particle? For instance, perhaps one could model nucleon interactions deterministically and observe that when the...
  48. C

    What is the underlying mechanism of nuclear decay?

    I think I understand the basics of the SM and know that the W and Z bosons are the mediators of the Weak Force. I also understand from chem the basics about nuclear stability (ratio of protons to neutrons, valley of stability/nuclear binding energy, etc.). What I'd like to know is what the...
  49. K

    Half life of a nuclear decay via simulation

    I don't know how to solve the questions that my lecturer gave me. I not understand about probability of half life. Can anyone explain to me and help me solve the questions as well? My lecturer ask us to prove the probability as shown in the picture.