# Find product kinetic energies in (α,γ) reaction

1. Apr 28, 2017

### ElectricEel1

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.

Thanks

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. Apr 29, 2017

### 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.