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Detecting Neutrinos

2 Radioactive Decay

This is section 2 of 13.

An atom exists in a state of equilibrium, between its nucleus and is collection of electrons in concentric shells.

An atom can make a change in an instant. These changes can be only in the electrons, or only in the nucleus, or in both.

Among these instantaneous changes:

Electron capture.

Alpha decay,
Beta decay,
Gamma decay,

Inverse beta decay

Each item will be described in turn.

Tthere are more events involving simultaneous actions in an atom, but these are relevant to neutrinos.

I have other publications which include the other events, such as my book Practical Atomic Model.

Before the individual behaviors, there is another critical behavior to note. There is a particle competition within the nucleus. A context in the nucleus determines its decay selection.

Usually unstable nuclides are clearly either "neutron rich" or "proton rich", with the former undergoing beta decay and the latter undergoing electron capture (or more rarely, due to the higher energy requirements, positron decay). However, in a few cases of odd-proton, odd-neutron radionuclides, it may be energetically favorable for the radionuclide to decay to an even-proton, even-neutron isobar either by undergoing beta-positive or beta-negative decay.

An often-cited example is the single isotope 64Cu  (29 protons, 35 neutrons), which illustrates three types of beta decay in competition.
Copper-64 has a half-life of about 12.7 hours. This isotope has one unpaired proton and one unpaired neutron, so either the proton or the neutron can decay. This particular nuclide (though not all nuclides in this situation) is almost equally likely to decay through proton decay by positron emission (18%) or electron capture (43%) to 64Ni, as it is through neutron decay by electron emission (39%) to 64Zn.



Whether a nucleus is proton-rich or neutron-rich determines which beta decay occurs. Both decays are described below.

2.1 Electron capture

The electron capture step of radioactive decay involves a proton in the nucleus capturing one of the electrons in orbit at some distance.

The capture results in a) the proton changing into a neutron, b) a drop in the nucleus positive charge occurring at the same instant with c) the drop in the electron count, d) the difference between the number of electrons and protons remains the same.

2.2 Alpha Decay

Alpha decay requires the nucleus has the structure where an alpha particle already exists on the periphery of the nucleus. At the moment of instability, this particle of 2 protons bound to 2 neutrons is ejected by the Coulomb's force between a positive alpha particle and the rest of the nucleus which is also positive. The force for this ejection is sometimes called the weak force. Alpha decay occurs in the heaviest elements, apparently starting at Tellurium isotopes which have 59 protons. Several of its isotopes having 52 or more neutrons do alpha decay.

An alpha decay has no accompanying emission of neutrino, but it usually has an accompanying gamma ray emission.

2.3 Beta Decays

Beta decay requires the nucleus change its charge by one electron charge, by either an increase by emitting 1e- (beta minus) or a decrease by emitting 1e+ (beta plus).

The two decays are explained further below.

Sometimes, beta decay has a gamma ray emission.

2.4 Gamma Decay

Gamma decay is not clearly described. This step is usually associated with the element radium. It is also often associated with the alpha decay.

A sample of radium metal maintains itself at a higher temperature than its surroundings because of the radiation it emits – alpha particles, beta particles, and gamma rays.

More specifically, natural radium (which is mostly 226Ra) emits mostly alpha particles, but other steps in its decay chain (the uranium or radium series) emit alpha or beta particles, and almost all particle emissions are accompanied by gamma rays.

In 2013, it was discovered that the nucleus of radium-224 is pear-shaped. This was the first discovery of an asymmetric nucleus.



The radium description offers insight into radioactive decay.

A nucleus lacking symmetry enables a loss in stability when equilibrium between forces is disturbed.

Due to the mechanism of their production in standard alpha radioactive decay, alpha particles generally have a kinetic energy of about 5 MeV, and a velocity in the vicinity of 4% of the speed of light.



Alpha decay emits a particle combination, having 2 protons and 2 neutrons, being ejected at high velocity, so this is a positive charge in motion. This event can be a source of electromagnretic radiation.

I find no record of the spectrum of the radiation from radium.

Gamma Ray wavelengths are less than 10pm.

X-ray wavelengths span from 10pm to 10nm.

The covalent radius of the radium atom is 221pm.

The radius of its nucleus must be much smaller.

With no data, there can be no suitable conclusion about the wavelength being emitted by radium.

The alpha particles apparently have the great velocity required for the energy of gamma rays to be propagated by their ejection from the nucleus.

By thermodynamics, energy cannot be created or destroyed, but can be transformed. The kinetic energy of the alpha particle is transformed into the energy in a wavelength of electromagnetic radiation.

The force for this alpha particle ejection is the electrostatic force between positive charges. The velocity is driven from their proximity, when the equilibrium holding a physical contact was disturbed.

2.5 Beta Plus Decay

There are 2 beta decays, beta-plus or beta-minus.

Beta plus decay is also called positron emission.

Positron emission or beta plus decay (B+ decay) is a subtype of radioactive decay called beta decay, in which a proton inside a radionuclide nucleus is converted into a neutron while releasing a positron and an electron neutrino (ve). Positron emission is mediated by the weak force. The positron is a type of beta particle (B+), the other beta particle being the electron (B-) emitted from the B- decay of a nucleus.

An example of positron emission (B+ decay) is magnesium-23 decaying into sodium-23.

Because positron emission decreases proton number relative to neutron number, positron decay happens typically in large "proton-rich" radionuclides. Positron decay results in nuclear transmutation, changing an atom of one chemical element into an atom of an element with an atomic number that is less by one unit.

A positron is ejected from the parent nucleus, and the daughter (Z-1) atom must shed an orbital electron to balance charge. The overall result is that the mass of two electrons is ejected from the atom (one for the positron and one for the electron).



This behavior is like an electron capture.

Both results are Z-1 and neutrons +1

The only apparent difference from their descriptions is the positron emission.

This is the frequently mentioned scenario with deay of 23Mg to 23Na

Start :
23Mg has 12Z + 11n, 12 e in orbit

After decomposing the neutron, the particles in the atom are 23p + 23e

23Na has 11Z + 12N, 11 e in orbit.

There is an alternate scenario, where no positron is created from a proton, which does not possess an internal positron to eject.
A long time ago, I read a description where an electron is shed during the B+ decay. I remember that specific word.

It implies the sodium atom is an ion at the end, not neutral.

Unfortunately, despite an prolonged search I cannot find its source.

For this investigation of beta plus decay, I will include that conjecture, as an alternative to consider.

This is a simultaneous capture of 2 electrons by the nucleus, not 1. The nucleus is seeking stability by pulling electrons into the nucleus.

This is the instantaneous event when every step is simultaneous, not sequential.

a) at the start is a nucleus with 23p and 11e (from Z=12, N=11), with 12e in orbit
b) 2e are captured by the nucleus from inner shell, where the expected capture is only 1.
c) at this instant, the nucleus has 23p with 13e; while there remain 10e in orbit,
d) the first e attaches to a proton becoming a neutron,
e) The errant 2nd electron's polarity is flipped from normal e– to e+ becoming a positron.
f) this positron is ejected from the nucleus by the electrostatic force between positive charges.
g) by ejecting that "flipped in an instant" positron, the bucleus tries to balance the charges.
h) at the end, the nucleus as 23p with 12e (Z=13, N=12) for 23Na, but with 10e in orbit
i) This is 23Na but not neutral, or an ion.
j) Therefore, the positron is the captured electron but its polarity was flipped by the nucleus.

The positron did not come from a proton.

The positron was an electron of the 12 in the atom's shells, but had its polarity flipped.

No mass was created or lost in the instantaneous event.

23Na is stable.

2.6 Beta-minus decay

From the nucleus competition description (above), beta minus decay occurs in a "neutron rich" nucleus.  As a result, one neutron ejects its accompanying electron due to too many electrons in the nucleus, among the protons, with some combinations as neutrons. Equilibrium among these electrons and their protons is restored by the ejection of one of the electrons.
In another section of this book, there is a known behavior with atoms having an odd count of both its ptotons (Z) and neutrons (N) are sometimes less stable.

The electro static force between negative particles drvives this electron ejection.

Here is its description.

In nuclear physics, beta decay (B 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. For example, beta decay of a neutron transforms it into a proton by the emission of an electron accompanied by an antineutrino.



Beta minus decay is accompanied by an electron antineutrino.

Beta-minus decay is also explained in section Fermi's Interaction

2.7 Inverse Beta Decay

This is a new behavior proposed for only neutrinos

Here is its description.

Inverse beta decay, commonly abbreviated to IBD, is a nuclear reaction involving an electron antineutrino scattering off a proton, creating a positron and a neutron. This process is commonly used in the detection of electron antineutrinos in neutrino detectors, such as the first detection of antineutrinos in the Cowan–Reines neutrino experiment, or in neutrino experiments such as KamLAND and Borexino. It is an essential process to experiments involving low-energy neutrinos (< 60 MeV) such as those studying neutrino oscillation, reactor neutrinos, sterile neutrinos, and geoneutrinos. The IBD reaction can only be used to detect antineutrinos (rather than normal matter neutrinos, such as from the Sun) due to lepton conservation.



A first impression of this description is this event is impossible.

An electron antineutrino has neglible mass, so it cannot possibly create 2 particles having substantial mass, a positron and neutron.

The description is very misleading.

The description implies the proton remains and both a positron and neutron are crested from only the antineutrino.

A better description would be an antineutrino hits a proton in a nucleus and that proton becomes a neutron.

The claimed neutrino event in an atom results in a combination just like a beta plus decay event.

These steps are instantaneous, not sequential.

1) the nucleus does an electron capture,

2) this is a proton becoming a neutron, so no particle is created,

3) the nucleus captures a second electron,

4) this is the second captured electron having its polarity flipped, so no particle is created,

5)  this is not an event triggered by a neutrino; this is an event in an element taking a step in a radioactivity sequence.

6) if a neutrino is claimed to bring energy to trigger this event, then that claim has no evidence.

This event of radioactivity did not require external energy of whatever amount was claimed in the neutrino.

This event of radioactivity is not evidence for a neutrino.

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last change 04/03/2022