beta decay[1]

8/3/2019 Beta Decay[1]

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RADIOACTIVITY

PENGENALAN ASTRONOMI

DAN

FIZIK MODEN

GROUP ASSIGNMENT

GROUPMEMBERS :


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Radioactivity

When an unstable nucleus releases energy and/or particles.


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Radioactive Decay

There are 4 basic types ofradioactive decay

Alpha Ejected Helium

Beta Ejected Electron Positron Ejected Anti-Beta

particle

Gamma Ejected Energy

You may encounter protons andneutrons being emitted as well

n

p

e

e

He

1

0

11

0

0

0

1

0

1

4

2

K


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Alpha decay is a type of radioactive decay

in which an atomic nucleus emits an alpha

particle and thereby transforms (or

'decays') into an atom with a mass number

4 less and atomic number 2 less.

For example:

4238 234 + 2He2+

92 90Th [1]

238 234

U Th + a


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.

An alpha particle is the same

as a helium-4 nucleus,

and both mass numberand

atomic number are the same

Alpha decay is by far the most common form of cluster

decay where the parent atom ejects a defined daughter

collection of nucleons , leaving another defined product behind

(in nuclear fission , a number of different pairs of daughters

of approximately equal size are formed).

Alpha decay is the most likely

cluster decay because of the

combined extremely high binding

energy and relatively small mass of the

helium-4 product nucleus (the alphaparticle).


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In nuclear physics, beta decay is a type of radioactive decay in which a beta particle (anelectron or a positronis emitted

In the case of electron emission, it is referred to as beta minus (), while in the case of apositron emission as beta plus (+)

In electron emission, an electron antineutrino is also emitted, while positron emission isaccompanied by an electron neutrino. Beta decay is mediated by the weak force.

Emitted beta particles have a continuous kinetic energy spectrum, ranging from 0 to themaximal available energy (Q), which depends on the parent and daughter nuclear states thatparticipate in the decay. A typical Q is around 1 MeV, but it can range from a few keV to afew tens of MeV. Since the equivalence of energy of the rest mass of electron is 511 keV, themost energetic beta particles are ultrarelativistic, with speeds very close to the speed of light

Sometimes electron capture decay is included as a type of beta decay (and is referred to as

"inverse beta decay"), because the basic process, mediated by the weak force is the same.However, no beta particle is emitted, but only an electron neutrino. Instead of beta-plusemission, an inner atomic electron is captured by a proton in the nucleus. This type of decay istherefore analogus to positron emission (and also happens, as an alternative decay route, in allpositron-emitters). However, the route of electron capture is the only type of decay that isallowed in proton-rich nuclides that do nothave sufficient energy to emit a positron (andneutrino). These may still reach a lower energy state, by the equivalent process of electron-capture and neutrino-emission.


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There are3 different modes of beta decay

Electron

emission

Electron capture

Position

emission


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Electron emitters are found

throughout the periodic table, from

the lightest elements (3H) to the

heaviest (255Es).

Electron

emission


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Electron capture

Leads to a decrease of one in the charge on the nucleus.

The energy given off in this reaction is carried by an x-ray

photon, which is represented by the symbol hv, where h is

Planck's constant and v is the frequency of the x-ray

The product of this reaction can be predicted, once

again, by assuming that mass and charge are

conserved.

The electron captured by the nucleus in this reactionis usually a 1s electron because electrons in this

orbital are the closest to the nucleus.


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Positron

emission

beta decay[1]

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