4%20Nuclear%20Fission0.ppt

For Even A odd Z odd N there will be nucleons which cannot pair with another with opposite spin. Such a state is less bound than the even-even case. Thus we need to add a pairing term which is: δ(A,Z) = +ap A-3/4 A even, odd-odd δ(A,Z) = 0 A odd δ(A,Z) = -ap A-3/4 A even, even-even The form of δ(A,Z) not given by liquid drop model. δ(A,Z) has a value ~0.5 pairing energy Total formula: The constants may be obtained empirically by fitting the equation to known masses. Relative Importance of the contributions to Nuclear Binding Energy A MeV/nuc Volume energy Surface energy Coulomb energy Symmetry energy Nuclear Fission Nuclear Fission Binding Energy Survey of Binding Energies Liquid Drop Model Nuclear Mass One mass unit = 1 u (unified mass unit) = 1/12 mass of neutral unexcited atom consisting of 12C nucleus and six electrons = 1.66043 x 10-27 kg 1.49…x 10-10 J 931.502 MeV Nuclear Binding Energy This is the energy released when appropriate numbers of neutrons and protons are combined to form a nucleus. Conversely, it is the energy required to separate the nucleus into its constituents. Binding Energy Because of Einstein’s mass-energy equivalence we can write for the nuclear binding energy:- Most mass measurements give atomic masses rather than nuclear masses so it is useful to write: where the masses are now atomic masses Nuclear Binding Energy Deuteron Binding Energy In class problem... mp = 1.00728u mn = 1.00867u Mass of deuteron is md = 2.01355u Find the binding energy of deuteron in MeV Nuclear Binding Energies /hbase/nucene/nucbin.html /people/jinseok/notes/notesnotesshtml Main features Positive binding energy for all nuclei i.e. Any nucleus is more stable than an unconnected assembly of its constituent neutrons and protons. This will be so if there are attractive nuclear forces between these constituents within the nuclear volume. Since nuclei do not collapse these forces must become repulsive f