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**? Nuclear Reactions Categorization of Nuclear Reactions**

According to: bombarding particle, bombarding energy, target, reaction product, reaction mechanism. Bombarding particle: Charged particle reactions. [ (p,n) (p,) (,) heavy ion reactions ]. Neutron reactions. [ (n,) (n,p) ….. ]. Photonuclear reactions. [ (,n) (,p) … ]. Electron induced reactions…………. Bombarding energy: Thermal. Epithermal. Slow. Fast. Low energy charged particles. High energy charged particles. ? Neutrons. Nuclear and Radiation Physics, BAU, Second Semester, (Saed Dababneh).

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**Nuclear Reactions Pickup Resonant Stripping Non-resonant Targets:**

Light nuclei (A < 40). Medium weight nuclei (40 < A < 150). Heavy nuclei (A > 150). Reaction products: Scattering. Elastic 14N(p,p)14N Inelastic 14N(p,p/)14N* Radiative capture. Fission and fusion. Spallation. ….. Reaction mechanism: Direct reactions. Compound nucleus reactions. More in what follows …. What is a transfer reaction….????? Pickup Resonant Stripping Non-resonant Nuclear and Radiation Physics, BAU, Second Semester, (Saed Dababneh).

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**Reaction Cross Section(s) (Introduction)**

Probability. Projectile a will more probably hit target X if area is larger. Classically: = (Ra + RX)2. Classical = ??? (in b) 1H + 1H, 1H + 238U, 238U + 238U Quantum mechanically: = 2. Coulomb and centrifugal barriers energy dependence of . Nature of force: Strong: 15N(p,)12C = 0.5 b at Ep = 2 MeV. Electromagnetic: 3He(,)7Be = 10-6 b at E = 2 MeV. Weak: p(p,e+)D = b at Ep = 2 MeV. Experimental challenges to measure low X-sections.. HW 33 Nuclear and Radiation Physics, BAU, Second Semester, (Saed Dababneh).

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**Reaction Cross Section(s) (Introduction)**

Detector for particle “b” d Ia “b” particles / s , cm2 “X“ target Nuclei / cm2 “a” particles / s Typical nucleus (R=6 fm): geometrical R2 1 b. Typical : <b to >106 b. Nuclear and Radiation Physics, BAU, Second Semester, (Saed Dababneh).

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**Reaction Cross Section(s) (Introduction)**

Many different quantities are called “cross section”. Krane Table 11.1 Angular distribution Units … ! “Differential” cross section (,) or ( ) or “cross section” …!! Doubly differential t for all “b” particles. Energy state in “Y” Nuclear and Radiation Physics, BAU, Second Semester, (Saed Dababneh).

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**Nuclear and Radiation Physics, BAU, Second Semester,**

Coulomb Scattering Elastic or inelastic. Elastic Rutherford scattering. At any distance: V = 0 Ta = ½mvo2 l = mvob vmin vo rmin b d Nuclear and Radiation Physics, BAU, Second Semester, (Saed Dababneh). No dependence on

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Coulomb Scattering Nuclear and Radiation Physics, BAU, Second Semester, (Saed Dababneh).

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**Coulomb Scattering b < b > db d HW 34**

n target nuclei / cm3 x target thickness (thin). nx target nuclei / cm2 HW 34 Show that and hence b Rutherford cross section Nuclear and Radiation Physics, BAU, Second Semester, (Saed Dababneh).

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**Coulomb Scattering HW 35 Study Fig. 11.10 (a,b,c,d) in Krane**

See also Fig in Krane. HW 35 Show that the fraction of incident alpha particles scattered at backward angles from a 2 m gold foil is 7.48x10-5. Nuclear and Radiation Physics, BAU, Second Semester, (Saed Dababneh).

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**Coulomb Scattering Elastic Rutherford scattering.**

Inelastic Coulomb excitation. See the corresponding alpha spectrum of Fig in Krane. Nuclear and Radiation Physics, BAU, Second Semester, (Saed Dababneh).

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Coulomb Scattering Nuclear and Radiation Physics, BAU, Second Semester, (Saed Dababneh).

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**Nuclear Scattering Elastic or inelastic. Analogous to diffraction.**

Alternating maxima and minima. First maximum at Minimum not at zero (sharp edge of the nucleus??) Clear for neutrons. Protons? High energy, large angles. Why? Inelastic Excited states, energy, X-section and spin-parity. Nuclear and Radiation Physics, BAU, Second Semester, (Saed Dababneh).

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