Question

Find the threshold energy that the incident neutron must have to produce the reaction

1 n 0 + 4 He 2---> 2 H 1 + 3 H 1

For this, like the 1 n 0<--- it is supposed to be written like 1 on the top 0 on the bottom next to n. like the atomic number of neutron and the other elements.

You will need to look up the masses of each of those particles. There will be slightly more mass on the right side, since energy is needed to make the reaction happen. Call the meass difference "delta M"

The threshold incident neutron energy, from the Einstein E=mc^2 law, is
E = c^2 * (delta M)

That is the energy required in "center of mass"-fixed coordinates. Since the neutron is moving and the helium nucleus is fixed in the lab coordinate system, a somewhat higher nuetron energy will be required, in order for the energy available in a coordinate system fixed with the center of mass to equal E. The initial speed of the neutron in CM system will be 4/5 of the speed in lab coordinates