Presentation is loading. Please wait.

Presentation is loading. Please wait.

Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh). 1 Compound Nucleus Reactions Direct CN decays Time. Energy. Two-step reaction.

Similar presentations


Presentation on theme: "Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh). 1 Compound Nucleus Reactions Direct CN decays Time. Energy. Two-step reaction."— Presentation transcript:

1 Nuclear and Radiation Physics, BAU, First Semester, (Saed Dababneh). 1 Compound Nucleus Reactions Direct CN decays Time. Energy. Two-step reaction. CN forgets how it was formed. Decay of CN depends on statistical factors that are functions of E x, J. Low energy projectile, medium or heavy target. Q CN E a CM

2 Nuclear and Radiation Physics, BAU, First Semester, (Saed Dababneh). 2 Compound Nucleus Reactions

3 Nuclear and Radiation Physics, BAU, First Semester, (Saed Dababneh). 3 Compound Nucleus Reactions Consider p + 63 Cu at E p CM = 20 MeV. Calculate E p + [m( 63 Cu) + m(p) – m( 64 Zn)]c 2. Divide by 64 available energy per nucleon << 8 MeV. Evaporation Multiple collisions long time statistical distribution of energy small chance for a nucleon to get enough energy Evaporation. Higher incident energy more particles evaporate. See also Fig in Krane.

4 Nuclear and Radiation Physics, BAU, First Semester, (Saed Dababneh). 4 Random collisions nearly isotropic angular distribution. Direct reaction component strong angular dependence. See also Fig in Krane. Direct Reactions

5 Nuclear and Radiation Physics, BAU, First Semester, (Saed Dababneh). 5 Direct Reactions Peripheral collision with surface nucleon. 1 MeV incident nucleon ?? more likely to interact with the nucleus CN reaction. 20 MeV incident nucleon ?? peripheral collision Direct reaction. CN and Direct (D) processes can happen at the same incident particle energy. Distinguished by: D ( s) CN ( s). [Consider a 20 MeV deuteron on A=50 target nucleus]. Angular distribution.

6 Nuclear and Radiation Physics, BAU, First Semester, (Saed Dababneh). 6 Direct Reactions (d,n) stripping (transfer) reactions can go through both processes. (d,p) stripping (transfer) reactions prefer D rather than CN; protons do not easily evaporate (Coulomb). [ (p,d) is a pickup reaction]. What about (,n) transfer reactions? HW 36 HW 36 Show that for a (d,p) reaction taking place on the surface of a 90 Zr nucleus, and with 5 MeV deuterons, the angular momentum transfer can be approximated by l = 8sin( /2), where is the angle the outgoing proton makes with the incident deuteron direction. (Derive a general formula first). l º14.4º29º44º J ( 90 Zr gs ) = 0 + J ( 91 Zr) = l ± ½, = (-1) l Optical model, DWBA, Shell model, Spectroscopic Factor. Fig in Krane.

7 Nuclear and Radiation Physics, BAU, First Semester, (Saed Dababneh). 7 Neutron-induced Reactions X ( n,b ) Y n ( E n ) b ( Q + E n ) For thermal neutrons Q >> E n b ( Q ) constant Probability to penetrate the potential barrier P o ( E thermal ) = 1 P > o ( E thermal ) = 0 Non-resonant

8 Nuclear and Radiation Physics, BAU, First Semester, (Saed Dababneh). 8 Neutron-induced Reactions


Download ppt "Nuclear and Radiation Physics, BAU, First Semester, 2007-2008 (Saed Dababneh). 1 Compound Nucleus Reactions Direct CN decays Time. Energy. Two-step reaction."

Similar presentations


Ads by Google