It is desired to study the first excited state of oxygen, which is at an energy of 6.049 MeV. (a) Using the (a, n) reaction on a target of ¹³C,

what is the minimum energy of incident alphas which will populate the excited state? (b) In what direction will the resulting neutrons travel? (c) If it is desired to detect the neutrons at 90° to the incident beam, what is the minimum a energy that can result in the excited state being populated?