1. NUCLEAR ENERGY LEVELS
CHAPTER-V

2. POINTS TO BE STUDY 5.1 Alpha decay- α disintegration energy
5.2 α particle spectra
5.3 Nuclear energy levels
5.4 Beta decay –Experimental study of β decay 5 .5 Continuous β ray spectrum
5.6 Pauli’s neutrino hypothesis
5.7 Nuclear energy levels from β decay

3. RADIOACTIVITY
The phenomenon of spontaneous emission of highly penetrating radiations from radioactive substance is called “Radioactivity” The emitted radiations are α, β and γ rays

4. α- Decay
Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and thereby transforms or 'decays' into an atom with a mass number that is reduced by four and an atomic number that is reduced by two.

5. β- Decay
In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta ray(fast energetic electron ), and a neutrino are emitted from an atomic nucleus.

6. α- Ray Spectra X X X X X X X X X X X X X X X X X X X X X X X X X X X X
Magnetic Field
Evacuated Chamber (C)
To Pump
X X X X X X X
X X X X X X X
X X X X X X X
X X X X X X X
X X X X X X X
X X X X X X X
Photographic Plate (P) S

7. FINE STRUCTURE OF α- LINE
6.09
α5= MeV
0.621
α4= MeV
α3=5.734 MeV γ
α2= MeV
Energy
in eV
α1= MeV
0.493
α0= MeV γ
0.473 γ
0.328 γ
0.04 γ
Ground State

8. LONG RANGE α- PARTICLE SPECTRUM
ThC ( 83Bi212) β β
ThC1 ( 84Po212) β β
1.793 MeV γ
1.772 M.eV γ
0.726 MeV γ
0 MeV
Ground State
α4 ( MeV)
α3 ( MeV)
α2 ( 9.671MeV)
α1 ( MeV)
ThD ( 82Pb208)
Ground State

9. β-Decay

10. 1)β-Decay by emission of electron
0n H e γ
Neutron proton electron antineutrino
2) β-Decay by emission of positive electron.
1H n e γ
proton neutron positron neutrino
K- electron capture
P e n1
zXA e z-1YA

11. β- Ray Spectra D A X X X X X X X X X X X X X X X X X X X X X
Magnetic Field
Evacuated Chamber (C)
To Pump
X X X X X X X
X X X X X X X
X X X X X X X D
X X X X X X X
X X X X X X X A
X X X X X X X
Photographic Plate (P) S

12. CONTINEOUS β- RAY SPECTRUM
Tav = 1/3Tm
Nmax = No N
End Point Energy Tm T0
K.E

13. Pauli’s Neutrino Hypothesis
According to Pauli, In each β-disintegration an additional particle is emitted along with β particle. It was assumed to be neutral to maintain conservation of charge. It has zero rest mass to maintain law of conservation of energy and linear momentum. It has given the name “neutrino”. This postulate is called Pauli’s neutrino hypothesis. Neutrinos are ‘fermions’ Spin equal to ½. They moves with velocity of light. n p+ + e- +γ i.e 0n1 1H1 + -1e0 + γ