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Nuclear Reaction

  1. Aug 1, 2010 #1
    How an endoergic nuclear reaction can be modified physically to get exoergic one?
  2. jcsd
  3. Aug 1, 2010 #2
    Also, is the Q value of a nuclear reaction difference in the kinetic energies of initial substances(incident particle and Target nucleus) and the kinetic energies of product substances or the difference in the kinetic energies of product substances and initial substances coz I found different definition of Q in different books.
  4. Aug 5, 2010 #3


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    Q is usually or customarily defined at the difference in mass-energies of the reactants minus (less) the mass-energies of the products, or if one assumes conservation of energy, then it would be the difference in kinetic energies of the products and reactants, since the kinetic energy of the reactants is carried over to the kinetic energy of the products.

    Conisder a reaction of particles a, b which react to produce particles c, d, i.e., a + b => c + d, and apply the conservation of (total) energy:

    Ti + (ma + mb) c2 = Tf + (mc + md) c2, where Ti is the initial kinetic energy, Tf is the final kinetic energy, and c is the speed of light, not to be confused with c the particle identity.

    Tf - Ti = ((ma + mb) - (mc + md)) c2 = Q

    An exothermic reaction requires that Q > 0, which requires (ma + mb) > (mc + md)

    Q is also defined as the energy released or absorbed in a nuclear reaction.

    In general, there is really no way to take an endothermic nuclear reaction and make it exothermic. The exception would be a reaction for which there is a threshold for a different outcome, i.e., an exothermic reaction as opposed to endothermic, e.g., a fission threshold, where a neutron of a certain energy is required to fission an atom as opposed to simply being absorbed and gamma photon emitted.

    One could simply change the projectile species, but that then changes the reaction.

    Q is related to binding energy. Please refer to

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