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Quantum numbers.
Quantum numbers;
In case of elementary particles, while considering reactions, we must consider various parameters. One of the major parameter is quantum numbers.
Baryon and lepton numbers
A set of quantum numbers is used to characterise baryons and three families of leptons.
Baryon and lepton numbers.
The significance of these numbers is that in any kind of reaction the total baryon numbers (B) and lepton numbers are conserved.
Baryon and lepton quantum numbers are conserved.
Strangeness number (S)
Gellmann and Nishijina introduced a new quantum number called strangeness quantum number. Strangeness number is assigned to strange particles, which are named due to their strange behaviour i.e they are produced via strong interaction or electromagnetic interaction, but they decay via weak interaction. Another fact about these particles is that they are always produced in pairs. The assignment of strangeness number to particle is shown in Table below.
Strangeness number of hadrons.
The antiparticles have the S value negative of shown above.
Strangeness number (S) are conserved in all process mediated by strong and electromagnetic interactions. Example in proton - proton collision.
Mass defect, packing fraction and binding energy: It was assumed that mass of the nucleus is equal to the mass of its constituents (i.e protons and neutrons). But experimentally it was found that the actual mass of the nucleus is less than the theoretical mass. Thus, the difference between the theoretical mass and experimental mass is called mass defect i.e ∆m={[Zmₚ + (A-Z)mₙ] - M} Where mₚ= mass of proton mₙ= mass of neutron M= actual mass of nucleus Z= atomic number A= mass number The ratio of mass defect and mass number (A) is called packing fraction (f) f = ∆m/A Thus packing fraction is the mass defect available per nucleon. The packing fraction explains the stability of the nucleus. The packing fraction may be positive, negative or zero. The positive value of packing fract...
Different kinds of beta decay 1) Negative beta decay process: When there is excess number of neutrons in the nucleus, the neutron is converted into proton with the emission of electron and antineutrino particle and this process is called negative beta decay process. Negative beta decay. 2) Positive beta decay process: When there is excess number of protons in the nucleus, the proton is converted into neutron with the emission of positron and neutrino particle and this process is called positive beta decay process. Positive beta decay. 3) Electron Capture: When there is excess number of protons in the nucleus, sometimes the nucleus will absorbed the nearby electrons in the nearest electron orbital emitting neutron and a neutrino and this process is called electron capture. Electron capture. 4) Inverse beta decay: Inverse beta decay. Thus such kind of reaction in which neutrinos are absorbed to create some sort of beta decay is called inverse beta decay. Inverse beta decay confirm t...
Beta decay; Beta decay is a spontaneous radioactive decay process in which either a neutron gets converted into proton or a proton gets converted into neutron with the emission of electron or positron respectively. Whenever proton or neutron are in higher energy level because they are in excess they get converted into another kind of particle and thus decreasing the energy of the system and increasing its stability. In ¹²B there are seven neutrons and five protons while in ¹²C there are six neutrons and six protons, since both protons and neutrons are fermions and no more than two same kind of fermions can occupy the given energy level. Thus the figure below shows the nuclear energy diagram of ¹²C and ¹²B. Since in ¹²B nucleus, there are two neutrons present in excess, if a neutron gets converted in proton, then this new proton occupies an energy level lesser in energy than that of neutron and thus giving a stable ¹²C nucleus. Pauli theory of beta decay; An interesting historical ...
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