Chapter 1 Structure of matter Chapter 2 Nuclear transformation

What is Radiation? Radiation is Energy that is transmitted without the need for a material medium Electromagnetic Wave as an Example of Radiation 1387 p. Shokrani

The Electromagnetic Spectrum Radiation Wavelength in Angstrom Units Photon Energy in Million Electron Volts (MeV) 10 8 6 4 2 1 10 -2 -4 -6 X-Rays Radio Infrared V i s b l e Ultra-Violet Light Gamma Rays Cosmic Rays - -8 1 10 1387 P. Shokrani

1387 p. Shokrani

1387 p. Shokrani

A B C

The nucleus A the mass number (Nproton+ Nneutron) Z the atomic number (Nproton ) isotope same Nproton, different Nneutron isotone same Nneutron, different Nproton isobar same (Nneutron+ Nproton), different Nproton isomer  same Nproton, same Nproton, different nuclear energy state

Charts of isotopes Z=N Isotone Isotope Isobar

Atomic mass and energy units 1 amu = mass of =1.6610-27 kg 1 eV =1 V1.602 10-19 C =1.602 10-19 J Einstein’s principle of equivalence of mass and energy

Summary of Masses Masses Particle kg u MeV/c2 Proton 1.6726 x 10-27 1.007276 938.28 Neutron 1.6750 x 10-27 1.008665 939.57 Electron 9.109 x 10-31 5.486x10-4 0.511 1387 p. Shokrani

Classification of Forces in Nature There are four distinct forces observed in interaction between various types of particles

Classification of Fundamental Particles Two classes of fundamental particles are known: Quarks are particles that exhibit strong interactions Quarks are constituents of hadrons with a fractional electric charge (2/3 or -1/3) and are characterized by one of three types of strong charge called color (red, blue, green). Leptons are particles that do not interact strongly Electron, muon, tau, and their corresponding neutrinos.

Ionizing Photon Radiation Ionizing photon radiation is classified into four categories: Characteristic x ray Results from electronic transitions between atomic shells. Bremsstrahlung Results mainly from electron-nucleus Coulomb interactions. Gamma ray Results from nuclear transitions. Annihilation quantum (annihilation radiation) Results from positron-electron annihilation

انرژي پيوند هسته اي منشاء گداخت و شكافت هسته اي انرژي پيوند هسته اي منشاء گداخت و شكافت هسته اي This is a graph of the nuclear binding energy.   In this curve, you can see the variation of the binding energy per nucleon with respect to the atomic mass number. Beginning with introducing some terminology like nucleon and binding energy which appear on the y-axis here, I will explain what the configuration of the curve tells us and, eventually, how and why we can utilize the atomic energy in two different ways: nuclear fission and nuclear fusion. As most of you know, the famous formula of Albert Einstein, E = mc2, tells us that mass is equivalent to energy. The nucleus of an atom is composed of some tiny particles called nucleons. What is interesting is that the mass of a nucleus is always less than the sum of the individual masses of its nucleons.  This is because a nucleus consumes more energy to bind its nucleons together, and according to Einstein's formula, the reduced mass of the nucleus is expressed by this consumed energy. This difference of energy is called the binding energy. The y-axis of the graph is the binding energy of a nucleus divided by the number of its nucleons and the x-axis indicates the mass number of an atom, which is equal to the number of the nucleons in the atom, representing all the elements on the earth. Now that you are introduced to the definition of the components of the x and y axes in this curve, I'd like to explain what the configuration of the curve indicates and what physical meanings this diagram has in terms of energy production. First, noting that the higher binding energy per nucleon an element has, the more stable it is because it is difficult to divide the nucleus due to its strong binding energy per nucleon.  In this respect, the element that has the highest binding energy per nucleon in this region is the most stable substance on the earth and the mass number, in this case, is 56, which is iron! This explains why there is an abundant amount of iron in the universe. More importantly, as we observe this diagram, we can see there are two possibilities to produce energy. The left part of the curve from the peak indicates that, by combining two light elements, say hydrogen nuclei, into one heavier nucleus, we can produce energy by this difference in the binding energy per nucleon. On the other hand, if we split a heavy nucleus, such as uranium, into lighter nuclei, a certain amount of energy is produced by this difference. These two mechanisms are nuclear fusion and fission, respectively. There is also a big difference between nuclear fusion and fission besides their apparently opposite ways to produce energy; the amount of the produced energy is much greater in nuclear fusion than in fission. However, which mechanism do you think we are using today to generate electricity, fusion or fission? (waiting for any response..^^) Right, it’s fission. Even though the nuclear fusion has some conspicuous advantages such as huge amount of energy production, abundance in fuel, or friendliness with environment, there are also technical difficulties to make fusion reactions take place in an artificial and controlled manner. Therefore, the already well-established technology to utilize this binding energy, nuclear fission, is being commercially used today. At the same time, however, many institutions and universities in many countries, including MIT, are doing research and development to harness this fascinating, but challenging, energy source, nuclear fusion. 1387 p. Shokrani

كاستي (كاهش) جرم Mass Defect 1387 p. Shokrani

Fission Products محصولات فيژن 1387 p. Shokrani

Decay constant ()

Activity 1 Ci =3.71010 disintegrations/sec =3.71010 dps =3.71010 Bq

The half-life (T1/2) & the mean life (T)

Radioactive equilibrium

Transient equilibrium T1>T2 (1<2) Transient equilibrium time activity

Secular equilibrium T1>>T2 (1<<2) A2 = A1 activity time activity

 particle decay Q = the disintegration energy = the difference in mass between the parent nucleus and product nuclei E   510 MeV (discrete energy)

Negatron(-) emission An excessive number of neutrons or a high neutron-to-proton (n/p) ratio anti-neutrino Q = the difference in mass between and the sum of the masses of and the particles emitted.

Positron(+) emission A deficit of neutrons or a low n/p ratio neutrino Annihilation 0.511 MeV photon + positron  free electron

The -ray spectrum The average energy of the  particles is approximately Emax/3.

Electron capture The unstable nuclei with neutron deficiency may increase their n/p ratio by EC. An alternative process to the positron decay K capture characteristic x-rays (L or M capture) Auger electrons

Characteristic radiation An empty hole in a shell is filled by electron from outer shell with an emission of characteristic radiation. discrete energy h=EK - EL hole K L M

Auger Electrons The absorption of characteristic x-rays by orbital electrons and reemission of the energy in the form of monoenergetic electrons discrete energy E=h-EM=EK – EL-EM K L M hole

Internal conversion Conversion electron from K shell E = h-Eb K Nuclear  ray h Hole in K shell The excess nuclear energy is passed on to one of the orbital electrons which is then ejected from the atom. To create a vacancy in the involved shell, resulting in the production of characteristic photons or Auger electrons

Nuclear reactions (1) The , p reaction The , n reaction Threshold energy AX (, p) A+3Y The , n reaction Proton bombardment Deuteron bombardment

Nuclear reactions (2) Neutron bombardment Photon disintegration Neutron, no electric charge effective in penetrating the nuclei and producing nuclear reactions n,  reaction Photon disintegration Fission Chain reaction Fusion

Activation of nuclides The yield of a nuclear reaction The number of bombarding particles The number of target nuclei The probability of the occurrence Cross-section 1 barn = 10-24 cm2 The growth of activity Saturation activity

Thank you for your attention!