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Find product kinetic energies in (α,γ) reaction

  1. Apr 28, 2017 #1
    1. The problem statement, all variables and given/known data

    5.5 MeV alphas hit Be-9 and produce carbon with a gamma. the Q value is 10.65

    I have to find the kinetic energy of the carbon nucleus and the gamma and im to ignore the gamma ray momentum.

    2. Relevant equations
    T = p^2 / 2*m
    Q = T_be + T_alpha - T_c - T_gam

    3. The attempt at a solution

    Momentum is conserved and I'm told to ignore the gammas momentum so I calculated the alpha momentum to be 202.56 MeV/c then used that as the carbon momentum and rearranged to find the kinetic energy as 1.7 MeV.

    Then using the Q equation i rearranged to find T_gam but end up with -6.85 which doesn't work so I'm a little stuck now.


    edit: realised i had the equation the wrong way round and it should be Q = T_c + T_gam - T_alph

    think it makes sense now
    Last edited: Apr 28, 2017
  2. jcsd
  3. Apr 29, 2017 #2


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    2017 Award

    Staff: Mentor

    That's how I interpreted the Q-value as well.
    You can also check the masses of the nuclei to be sure, but the reaction certainly releases energy. C-12 is a very tightly bound nucleus.
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