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.)
I know the mass of J/ψ to be 3097 mev and the mass of phi to be 1018 mev. I know that J/ψ decays to electron and positron 5% of the time. I also know the full width of j/psi to be 0.092mev and that the phi meson lives 50 times longer than J/ψ
. My professor claims that if I am given that info...
i have some questions about decay rate.
1：why do we need decay rate in these equations?
2：is it a constant for a specific medium?
3：it can be changed with respect to some conditions like temprature or pressure?
4：how can i know the decay rate of some energy levels in 85Rubidium
I am studying the following process: pion decays (mediated by the charged ##W## boson) into a muon and anti-muon neutrino (i.e. ##\pi^- \to \mu + \bar{\nu}_{\mu}##). The Feynman diagram associated to it is
And its Feynman amplitude is (where we of course neglected...
Homework Statement
Given a coupling h \; \partial_\mu \phi^a \partial^\mu \phi^a , meant to model the first order interaction of the Higgs field h to boson fields \phi^a , compute the width \Gamma(h \rightarrow \phi^3 \phi^3) of the Higgs particle to decay to two longitudinal (say)...
Homework Statement
I need to calculate the muon decay rate, ignoring the mass of the outgoing particles.
Homework Equations
##d\Gamma = \frac{1}{2E_1}|M|^2d\Pi_{LIPS}##
The Attempt at a Solution
I am actually having problem with the math at a point. I reached this...
Regarding the Quantum Anti-Zeno effect (AZE), we know that frequent measurements of a decaying system (such as a decaying radioactive nucleus) can induce greater decay rates.
However, if I understand correctly, you can change the percentage of change in the decay rate. For example, if you have...
I recently read about a beta decay isotope (Rhenium-187),whose half life was changed from 42 X 109 years to 33 years, just by stripping the nucleus of all it's electrons. Why does this allow for a faster decay, and does this apply to all beta decay nuclei, or just Rhenium 187?
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...
Hey everyone,
I've learned about double beta decay and neutrinoless double beta decay recently. So we have two "conditions" for decay, 2v decay and 0v decay. Now, to the question I have:
There have been a lot of experiments measuring 2v decay rates, and there have been many experiments...
Homework Statement
Consider the process of decay of a muon into one electron, one electron antineutrino and one muon neutrino using the Fermi theory. Assume the matrix element is, ignoring the electron's and the two neturino's masses,
|\mathcal{M}|^2 = 32G_F^2(m^2-2mE)mE
being E the electron...
Hi All,
First time poster here, and I've got a couple questions. Straight up, I'm writing a sci-fi story where antimatter is utilised as fuel (feel free to laugh at the cliche), and I want to portray it as realistically as possible. To that end, I've come up with a storage method and I want to...
Why is the probability of one-photon loss from a cavity in the time interval ##[t, t+\delta t]## is:
##\kappa \delta t\langle \psi(t)| \hat{a}^{\dagger}\hat{a} |\psi(t)\rangle##
where ##\kappa## is the decay rate. It looks like the Fermi Golden rule but it's not exactly it.
I have been reading through Mukhanov's book "Physical Foundations of Cosmology" and have reached the section where he discusses the process of reheating. In it he mentions that the decay of the inflaton into bosonic states can be "Bose enhanced", i.e. that if ##n## previously created particles...
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...
Homework Statement
A muon decays to an electron, an electron neutrino and a muon neutrino. ## \mu \rightarrow e \ \nu_\mu \ \nu_e## .The matrix element of the process is ## |\mathcal{M}|^2 = G^2_F (m^2-2mE)mE## with ##m## being the mass of the muon and ##E## the energy of the resulting...
Homework Statement
An initially pure 3.4 g sample of Ga-67, an isotope with a half life of 78 hr.
What is its initial decay rate?
Note: Molar Mass values given in tables for chemical elements are for natural mix isotopic ratios. (i.e. the relative percentages of each isotope normally present...
From particle data group,(http://pdg.lbl.gov/2014/listings/contents_listings.html)
I can see the decay branching ratios of N(1875),but the total width is not found.The "Breit Wigner width " are very different.So my question is ,How do they get the branching ratio without a certain total width?
My textbook says:
One of the decays occurs via a ## b \to c ## quark transition and is 'colour-allowed'.(Left of diagram).
The other decay has a of ## b \to c ## and is 'colour-suppressed'.(Right of diagram)
I'm unsure of what is meant by these terms, it doesn't really explain.
I've...
In euclidean quantum field theory, the imaginary part of the free energy, defined as the logaritm of the partition function, is it connected to the decay rate?
Is there any thing that could, or any way to increase the atomic decay rate of already unstable elements, such as the radio active elements. magnetically or otherwise, even if the thought is only plausible or otherwise theory, I wouldn't mind hearing it.
A thought accord to me, what if...
Homework Statement
The nuclide (32,15)P undergoes Beta - decay with a half-life of 14.3 d. It is used as a tracer isotope in biochemical analysis. What is the initial decay rate of a 1.2mg sample?
Homework Equations
T1/2 = Ln 2 / λ
Ro = λN0
The Attempt at a Solution
I first...
Hi all,
I'm studying Laplace transform right now. And I am trying to understand the s variable in the s-plane. I found online that s = σ + jω where ω is the frequency and σ is the decay rate. Frequency is pretty easy to understand but I can't seem to find anywhere that explains what is the...
I read a book in which it proposed that anti-matter "decayed" faster than matter, right after the big bang, which is why there isn't an around. Unfortunately, I've forgotten exactly what the writer meant, and who it was...
Can someone tell me who the writer was, and in what book it was...
Homework Statement
The equilibrium concentration of C14/C12 ≈ 1.5×10−12
A 2.5 g sample of Carbon from an old tree fragment has an activity of 4.57 decays per minute. How old is the sample?
Homework Equations
I'm pretty sure I use A(t)=λN(0)*exp(-tλ)
but I am having trouble calculating N(0)...
How can I find the decay rate of carbon? I have found the decay constant and I know the half life and the number of atoms. I think I have the data and I have the answer but I think I am using the wrong equation as my answer does not fit the books.
The decay constant I got as -1.209x10^-4...
Homework Statement
If we have the following partial decay chain:
N1 -> N2 -> N3 where N1 is the number of nuclei of species 1, etc.
and N1 -> N2, not via a decay but by the reaction such as N1 + neutron -> N2 + photon
and we know this rate of formation of N2, say 'a'.
I then get the...
If we have the following partial decay chain:
N1 -> N2 -> N3 where N1 is the number of nuclei of species 1, etc.
and N1 -> N2, not via a decay but by the reaction such as N1 + neutron -> N2 + photon
and we know this rate of formation of N2, say 'a'.
I then get the following rate...
Homework Statement
You have two samples that exhibit radioactive decay. The first gives you initially a 1000/s decay rate and after one hour a 500/s decay rate. The second gives you initially a 500/s decay rate and after one hour a 250/s decay rate. Which sample has a higher probability per...
Hello! i was just wondering if anyone could help me with this,
The rubidium isotope 87-Rb is a beta emitter with a half life of 4.9 x 10^10 yr that decays into 87-Sr. It is used to determine the age of rocks and fossils. Certain rocks contain a ratio of 87-Sr to 87Rb of 0.0100. Assuming there...
Hi.
We are given a table containing values of mass(m) and time(t). We have been asked to plot graphs of (m) against (t) and then log(m) against (t).
The question is:
FROM YOUR GRAPHS, DETERMINE THE FUNCTION FOR THE RATE OF DECAY.
Of course i know the formula but have no clue how to...
Hello everyone,
I'm using the chiral perturbation theory for mesons to calculate Vector into two Pseudoscalars decay rates - hopefully to be able to calculate Tensor into two pseudoscalars decay rates later on.
I've got the lagrangien for the \rho \to \pi \pi decay rate :
L= f_{\rho...
Hi,
I am trying to understand exactly how and why the lifetime, or decay rate, of an atomic level determines the spectral width of the transition to this level. Also I would like to understand why the natural lineshape is a Lorentzian. I am familiar with the vague explanations involving...
Hi,
I'm trying to solve problem 48.4 of Srednickis QFT-Book. It goes something like this:
Homework Statement
We have a scalar field with mass M and a Dirac field with mass m (M>2m). The interaction part of the lagrangian is
L_a = g \varphi \bar{\Psi}\Psi
L_b = g \varphi...
Homework Statement
Its not a specific homework problem, buta general problem that a friend and I keep arguing about it.
Assume you have a system of:
N Particles.
2 Possible States, A && B
@ t=0 all N particles are in state A (such that c_a*c_a = P_a = 1)
where c_a is the coefficient...
Homework Statement
Measurements of a certain isotope tell you that the decay rate decreases from 8337 decays/minute to 3174 decays/minute over a period of 5.00 days.
Homework Equations
R=Ro.e^-lamda/t
then T1/2 = ln(2)/lamda
The Attempt at a Solution
I converted all the units...
'A radioactive element has a 0.5 probability of decaying to a more stable element after a particular time-span T.
What is the instantaneous decay rate per unit volume? In other words determine a general expression for the number of decay events occurring per unit volume between t=t1 and t=t2...
The decay rate of the Zo boson depends on the number of kinds of
neutrino.Does each kind of neutrino contribute to the decay rate equally?
Are there more electron neutrinos than muon or tau neutrinos?
do string make time or does time make strings , since strings have varoius vibrations, do there have a decay rate? just a question maybe one of you might know an answer?