It’s been a while since I posted any cute physics problems, so here’s a little one to amuse you this rainy Thursday morning.

In the following the notation A(a,b)B means the reaction a+A→b+B. The atomic number of Oxygen is 8 and that of Fluorine is 9.

The Q-value (i.e. energy release) of the reaction 19O(p,n)19F is 4.036 MeV, but the minimum energy of a neutron which, incident on a carbon tetrafluoride target, can induce the reaction 19F(n,p)19O is 4.248 MeV. Account for the difference between these two values.