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Nuclear and Radiation Physics, BAU, Second Semester, 2009-2010 (Saed Dababneh). 1 Basic Nuclear Properties Static nuclear properties (Time-independent):

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Presentation on theme: "Nuclear and Radiation Physics, BAU, Second Semester, 2009-2010 (Saed Dababneh). 1 Basic Nuclear Properties Static nuclear properties (Time-independent):"— Presentation transcript:

1 Nuclear and Radiation Physics, BAU, Second Semester, 2009-2010 (Saed Dababneh). 1 Basic Nuclear Properties Static nuclear properties (Time-independent): Electric charge, radius, mass, binding energy, angular momentum, parity, magnetic dipole moment, electric quadrupole moment, energies of excited states. Dynamic properties (Time-dependent): Self-induced (Radioactive decay). Forced (Nuclear reactions) cross sections. The key: Interaction between individual nucleons. Excited states: atomic intervals ~ eV. nuclear intervals ~ 10 4 – 10 6 eV. Decays and reactions: Conservation laws and selection rules. HWc 2 HWc 2 Where to find nuclear data???

2 Nuclear and Radiation Physics, BAU, Second Semester, 2009-2010 (Saed Dababneh). 2 Nuclear Mass (Introduction) Unified atomic mass unit u based on 12 C. Replaced both physical and chemical amu based on 16 O and natural oxygen, respectively (Find conversion factors). 1 u = M( 12 C)/12 = ……… kg = …………… MeV/c 2. Rest masses uMeV/c 2 kg electron ………… …………… ……… proton ………… …………… ……… neutron ………… …………… ……… 12 C12 …………… ……… Avogadros number.. !! What is the number of atoms in 1 kg of pure 238 U? Mass Stability. E = mc 2. Tendency towards lower energy Radioactivity. Neutron heavier than proton Free neutron decays (T ½ = ???):

3 Nuclear and Radiation Physics, BAU, Second Semester, 2009-2010 (Saed Dababneh). 3 Nuclear Mass (Introduction) Nuclear masses measured to high accuracy: mass spectrograph. energy measurement in nuclear reactions. Mass decrement = difference between actual mass and mass number: Δ = m – A Δ of parent(s) > Δ of product(s) radioactivity. Binding Energy? Stability? Fission? Fusion? More later …….. Usually atomic masses are tabulated. Mass of the atom < Zm H + Nm n.

4 Nuclear and Radiation Physics, BAU, Second Semester, 2009-2010 (Saed Dababneh). 4 The Valley of Stability

5 Nuclear and Radiation Physics, BAU, Second Semester, 2009-2010 (Saed Dababneh). 5 Nuclear Size Different experiments give different results Radius not well defined. Depends on probe and relevant physics. Probes should be close to the order of the size of the nucleus ~ 10 -14 m. Visible light? much larger. 1 MeV ? = ?? x 10 -12 m. Interacts with orbital electrons. Suitable probes: p, n,, e....Charge distribution. Mass distribution. All experiments agree qualitatively and somehow quantitatively. Project …. R A R = r 0 A with r 0 dependent on the method. Matter distribution charge distribution. [Recently some halo nuclei, e.g. 11 Li, found]. What is that?

6 Nuclear and Radiation Physics, BAU, Second Semester, 2009- 2010 (Saed Dababneh). 6 Nuclear Size 0 = nucleon density near the center. t = skin thickness. a = thickness parameter. R = Half-density radius. HW 4 Experiments show that t = (2.4 ± 0.3) fm for all nuclei t / R A -1/3 Is surface effect the same for all nuclei? HWc 3 Compare for A = 4, 40, 120 and 235.

7 Nuclear and Radiation Physics, BAU, Second Semester, 2009-2010 (Saed Dababneh). 7 Nuclear Size High-energy e scattering Light nuclei? R A From some experiments….! Charge distribution: r 0 = 1.07 fm. a = 0.55 fm. Matter distribution: r 0 = 1.25 fm. a = 0.65 fm. 0 decreases with A? YesNo Why?

8 Nuclear and Radiation Physics, BAU, Second Semester, 2009-2010 (Saed Dababneh). 8 Nuclear Size HW 5 Nucleus Z/ACharge density 40 Ca ….. ….. 59 Co ….. ….. 115 In ….. ….. 197 Au ….. ….. Charge radius ~ nuclear radius, even though heavy nuclei have more neutrons than protons. Explain… Density of ordinary atomic matter ~ 10 3 kg/m 3. Density of nuclear matter ~ 10 17 kg/m 3. Neutron stars, 3 solar masses, only 10 km across ….. !!! Surface effect?

9 Nuclear and Radiation Physics, BAU, Second Semester, 2009-2010 (Saed Dababneh). 9 Nuclear Size Three conclusions can be drawn: Inside the nucleus the density is fairly uniform. The transitional surface layer is thin. The central density has a similar value for different nuclei. Saturation? Get an estimate for nuclear density and thus inter- nucleon distance.

10 Nuclear and Radiation Physics, BAU, Second Semester, 2009-2010 (Saed Dababneh). 10 Nuclear Size Neutron Detector 1 Ci Pu-Be Neutron Source Absorber Beam From Optical Model Preferably low Different targets How can we get r 0 from the graph? HW 6 Dimensions


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