State and explain Alpha , Beta and Gamma decay

COMPLETE EXPLANATION OF ALPHA, BETA, GAMMA DECAY

1. State and explain , and decay   SYEDA NIMRA SALAMAT

2. -decay   Why there is a need of alpha decay? History State alpha decay + Generalized equation Explanation of alpha decay Gamow’s theory of alpha decay + Geiger Nuttall law Diagram + Table + Graph Examples Summary Syeda Nimra Salamat

3. Why there is a need of -decay?   Alpha decay   occurs most often in massive nuclei that have too large a proton to neutron ratio. Alpha radiation reduces the ratio of protons to neutrons in the parent nucleus, bringing it to a more stable configuration. Many nuclei more massive than lead decay by this method. Syeda Nimra Salamat

4. History: Alpha particles were first described in the investigations of radioactivity by Ernest Rutherford in 1899, and by 1907 they were identified as He2+ ions. By 1928, George Gamow had solved the theory of alpha decay via tunnelling.

5. State -decay + Generalized equation:   Syeda Nimra Salamat ‘A radioactive process in which a parent nuclei decay into daughter nuclei and alpha particle with some energy liberated.’ It is denoted by s the parent nucleus A is the total number of nucleons Z is the total number of protons is the daughter nucleus is the released alpha particle  

6. Explanation of –decay:   When an alpha particle are ejected from nucleus its mass number is reduced by four and atomic number reduced by two. This is occur to increase the stability of the nucleus. Alpha decay is a barrier penetration process. Imagine an alpha particle bounded by nuclear force and once it get out from the Nucleus it feels coulomb repulsive force. By using Gamow's theory of beta decay and Geiger Nuttal law. Syeda Nimra Salamat

7. Gamow’s Theory Of -Decay:   Syeda Nimra Salamat In different kind of alpha decay the maximum kinetic energy of the alpha particle is about 4-9MeV. While the energy of barrier penetration is of about 25MeV. The question here arises that how the alpha particle overcome such a large force and escape out. For this question Gamow introduces Gamow's theory of alpha particle. It is impossible to explain classically therefore we solve it quantum mechanically. He borrowed quantum tunnelling concept to explain this problem.

8. Quantum tunnelling: Syeda Nimra Salamat Here particle shows wave mechanical behaviour. It makes continuous strikes to overcome the barrier and penetrate through it. The transition probability of escape particle is given as;  

9. Gamow’s Theory Of -Decay :   Syeda Nimra Salamat We use two different elements to compare alpha particles of different kinetic energies. L is the width of barrier if width increase the transition probability decreases. The half life of high energy particle is less than low energy particle. )   For high energy –particle   For low energy –particle   L

10. Geiger Nuttall Law: Syeda Nimra Salamat It is basically the experimental observation Gamow's theory according to which; Short lived alpha particles have high kinetic energy while longer lived alpha particles have lesser kinetic energy. In this law the half life and kinetic energies of large number of alpha particles were observed undergoing decay process. the graph plotted between half life and kinetic energy is… The formula relation derived is given ;      

11. Table: Symbol Charge Mass Ionization energy Nature of radiation Relative penetrating power 2+ Intermediate 1 Symbol Charge Mass Ionization energy Nature of radiation Relative penetrating power 2+ Intermediate 1 Syeda Nimra Salamat Alpha decay

12. Examples: Alpha decay of radium-226 is; In this example an unstable atom is converted into stable atom by emission of an alpha particle. Alpha decay of radon gas into solid polonium and through emitting an alpha particle.   Syeda Nimra Salamat

13. Summary: Alpha decay  is one process that unstable atoms can use to become more stable. During  alpha decay , an atom's nucleus sheds two protons and two neutrons in a packet that scientists call an  alpha  particle. Since an atom loses two protons during  alpha decay , it changes from one element to another. Syeda Nimra Salamat

14. -decay   Why there is a need of alpha decay? History State alpha decay + Generalized equation Explanation of alpha decay + Neutrino Hypothesis Diagram + Table + Graph Examples Summary Syeda Nimra Salamat

15. Why there is a need of -decay?   Beta decay conserves a quantum number known as the number of electrons and their associated neutrinos. β+ decay also results in nuclear transmutation, with the resulting element having an atomic number that is decreased by one. Syeda Nimra Salamat

16. History: Beta decay was named (1899) by Ernest Rutherford when he observed that radioactivity was not a simple phenomenon. He called the less penetrating rays alpha and the more penetrating rays beta. Most beta particles are ejected at speeds approaching that of light.

17. State -decay + Generalized equation:   ‘Atoms emit beta particles through a process known as beta decay. Beta decay occurs when an atom has either too many protons or too many neutrons in its nucleus.’ It is denoted by symbol s the parent nucleus. A is the total number of nucleons. Z is the total number of protons. / are the daughter nucleus for – ve beta decay and + ve beta decay e-,e+ are the released beta particles for – ve beta decay and + ve beta decay Respectively.   Syeda Nimra Salamat

18. Neutrino Hypothesis: We can calculate the amount of energy whenever a nuclear reaction takes place. We also calculate the kinetic energy of the emitted particle. Here we theoretical predicted kinetic energy of the electron. But experimentally the electron has continuous distribution of kinetic energy. We perform an experiment in which we have kinetic energy of the particle but there exist a missing energy in compare of maximum expected kinetic energy. It can be seen that there is the violation of law of conservation of energy(complete energy is not present there is a missing kinetic energy). There occur three types of basic violations;(Wolf- Pouli notice in 1931) 1) Law of conservation of energy 2) law of conservation of linear momentum 3) law of spin angular momentum Syeda Nimra Salamat Expected K.E. on theoretical base K.E. of particle Missing energy

19. 1) Law of conservation of energy- As the total energy is not present there is missing energy 2) law of conservation of linear momentum- The recalling particle and the emitted particle (e-) should move in the same direction. But here 3) law of spin angular momentum- here we have } they all are fermions Which means each have half spin. but it is not balanced. E.Fermi in 1934 give a solution that there exist an other particle. 1) It should be neutral (from above equation the charge is balanced). 2) Tiny mass/ small rest mass. 3) Must have half spin so. It should be a fermion. They gave it the name NEUTRINO(little neutral one). Neutrino because spin and spin angular momentum are in opposite direction. Antineutrino because spin and spin angular momentum are in same direction.   Syeda Nimra Salamat  

20. Types of beta decay: Beta-Minus Decay: N egative beta decay releases a negatively charged beta particle called an electron and an antineutrino. + A neutron is transformed to yield a proton. N   Beta-Plus Decay: Positive beta decay releases a positively charged beta particle called a positron, and a neutrino. + The proton disintegrates to yield a neutron. P   Syeda Nimra Salamat

21. Table: Syeda Nimra Salamat Symbol Charge Mass Ionization energy Nature of radiation Relative penetrating power 1- intermediate electron 100 Symbol Charge Mass Ionization energy Nature of radiation Relative penetrating power 1- intermediate electron 100 Beta decay

22. Examples: The decay of carbon-14 is; In this example, a neutron of carbon is converted into a proton and the emitted beta particle is an electron. The β+ decay of carbon-10 is; In this example, a proton of carbon is converted into a neutron and the emitted beta particle is a positron.   Syeda Nimra Salamat

23. Summary: Beta decay occurs in two way positive beta decay and negative beta decay. The electron or positron emits plus the energy released in the form of neutrino or antineutrino. The atom become stable after the beta decay process. Syeda Nimra Salamat

24. -decay   Why there is a need of alpha decay? History State alpha decay + Generalized equation Explanation of alpha decay Diagram + Table + Examples Summary Syeda Nimra Salamat

25. History: Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900, while studying radiation emitted from radium. In 1914, gamma rays were observed to be reflected from crystal surfaces, proving that they were electromagnetic radiation.

26. State -decay + Generalized equation:   ‘A nucleus changes from a higher energy state to a lower energy state through the emission of electromagnetic radiation. Gamma rays cannot deflected by magnetic or electric field.’ It is denoted be symbol s the exited atom. s the relaxed state of initial atom. s the released gamma ray photon.   Syeda Nimra Salamat

27. Table: Syeda Nimra Salamat Symbol Charge Mass Ionization energy Nature of radiation Relative penetrating power Very high High energy photons 10,000 Symbol Charge Mass Ionization energy Nature of radiation Relative penetrating power Very high High energy photons 10,000 Gamma-decay

28. Explanation of –decay:   Syeda Nimra Salamat Most of the time, gamma decay occurs after the radioactive nuclei have undergone an alpha or a beta decay. The alpha and beta decays leave the daughter nuclei in an excited state. From the excited state, the daughter nuclei can get back to the ground state by emitting one or more high energy gamma rays. The spectra of gamma ray indicates that a nucleus can have several excited states, when an excited state return to its normal state gamma rays emitted.   Emission of after -decay   Emission of after -decay  

29. Examples: The -decay of barium-137. In this example the parent atom is lowered in energy. The decay of plutonium-240 . In this example the parent atom is lowered in energy.   Syeda Nimra Salamat *

30. Summary: The number of protons (and neutrons) in the nucleus does not change in this process, so the parent and daughter atoms are the same chemical element.’ Syeda Nimra Salamat

31. Result: Alpha ,  beta and gamma decay  are a  result  of the three fundamental forces working in the nucleus – the 'strong' force, the 'weak' force and the 'electromagnetic' force. In all three cases, the emission of radiation increases the nucleus stability, by adjusting its proton/neutron ratio. Syeda Nimra Salamat

32. Syeda Nimra Salamat

33. Thank You  Hope For The Best Syeda Nimra Salamat