What is Decay modes: Definition and 13 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. S

    Decay modes and lifetimes of hydrogen metastable states

    Protium atom has two low lying excited states with long lifetimes. These are: 2s. Decay energy would be 121 nm, but forbidden (no angular momentum difference). Fastest allowed decay is two-photon emission, lifetime 0,15 s Triplet 1s. Decay energy 211 mm. Prevalent decay single photon emission...
  2. F

    A Relation between chirality and spin

    When learning about chirality I was very surprised to find that for QED and QCD the decay modes that would produce 2 particles with the same chirality had a Matrix Element of 0, which I took to mean that angular momentum was being conserved. Even the W only decay into RH antiparticles and LH...
  3. X

    I Find Lambda Baryon Decays Cross Section Ratio

    I've been asked to find the ratio between the cross sections of the two folowing decais: Using the CKM matrix and the feynman diagrams for both decays, I reach the conclusion that the Ratio is exactly 1. However, consulting this document...
  4. U

    Psi Meson Decay Modes: Spin, Parity, Quark Content & More

    Homework Statement (a) Explain spin and parity of mesons (b) State their quark content (c) Draw a feynman diagram of J/psi decay (d) Why doesn't ##\chi## undergo leptonic decay? (e) What is the minimum centre of mass? [/B] Homework EquationsThe Attempt at a Solution Part(a)[/B] Spin is...
  5. binbagsss

    W+ decay modes neglect mass branching ratiosQ

    Homework Statement The question is that the decay modes for the ##W+## boson are , ##e^+ v_{e}, \mu^+ v_{\mu}, \tau^+ v_{\tau}, ud', cs' ##, where a ' denotes a anitquark, neglecting the masses of the decay products estimate the branching ratios of the ##W+##? Homework Equations N/A The...
  6. U

    Decoding the Mystery of Branching Ratios and Decay Rates

    Homework Statement (a) What are the branching ratios for EM decay only? (b) What does this reveal about the strength of strong interaction? (c)What are the relative rates of decay? Homework EquationsThe Attempt at a Solution Part (a) [/B] For EM-only decay, the branching ratio would be...
  7. S

    Guess Decay Modes: A, Z, Mass Diff MeV

    how can we guess the possible decay modes for an element with three given quantities: A, Z and mass difference in MeV
  8. J

    Maximum kinetic energy of a Pion produced via a kaon decay

    Homework Statement A possible decay mode a of a positive Kaon in the production of three Pions as shown below:. K+ → π+ + π+ + π− Whats is the maximum Kinetic energy that anyone of the pions can have? The kaon is a rest when...
  9. Z

    Uncovering the Mystery: Higgs Decay Modes and the Weight Paradox

    Under the Higgs in wiki it says "Another possibility is for the Higgs to split into a pair of massive gauge bosons. The most likely possibility is for the Higgs to decay into a pair of W bosons (the light blue line in the plot), which happens about 23.1% of the time for a Higgs boson with a mass...
  10. S

    Understanding the Different Modes of Potassium-40 Decay

    1)Is Potassium-40 dangerous material?How dangerous is it?Does it belong to restricted materials? 2)Why Potassium-40 decays in such different modes such as beta decay,electron capture, and positron decay?What could be done to prevent it decay in other ways with exept beta decay?Or what could be...
  11. J

    Questions about radiative decay modes

    Let's take for example the decay K+ -> pi+,pi0,gamma This can proceed via direct emission or inner bremsstrahlung. I have questions for each of these modes 1. For inner bremsstrahlung, it is a final charged product that radiates, correct? In this case the pi+. What is causing the...
  12. T

    Comprehensive List of Subatomic Particle Decay Modes and Probabilities

    Hello I'm looking for a list,as complete as possible, of decay modes and their probabilities, for all known subatomic particles. I've been googling, but found only bits and pieces. Perhaps someone knows a place on internet, or has found a free document to share, or anything like that thanks
  13. A

    What are the Decay Modes of the Higgs? Recommendations for Further Reading

    I need a reference describing the possible decay modes of the Higgs. Can anyone recommend any books or websites?