Nuclear PhysicsNuclear Physics

Selected TopicsSelected Topics

4 – Nuclear Reactions4 – Nuclear Reactions

The structure of nuclei can be changed by bombarding them with energetic particles.

The changes are called nuclear reactions.

As with nuclear decays, the atomic numbers and mass numbers must balance on both sides of the equation.

Alpha particle colliding with nitrogen:

Balancing the equation allows for the identification of X:

So the reaction is

4 14 12 7 1He N X H

17 17 8 8X X O

4 14 17 12 7 8 1He N O H

“Target” particles may be bombarded with

, neutrons, protons, deuterons, gamma.

General scheme:

a + X Y + b

Energy released:

Q = (Ma + MX – My – Mb).c2

Calculate Q for some reactions.

m (in u) = 1.007825 + 7.016003 – (2)(4.002602) = 1.8624 u = 17.3 meV

1 7 4 41 3 2 2H Li He He

This energy is the kinetic energy of the products.

Calculate Q for some reactions.

1 7 7 11 3 4 0H Li Be n

m = 1.007825 + 7.016003 – 7.016928 – 1.008665 = -.001765 u = -1.644 meV

The incident particle must have a minimum kinetic energy.

min 1m

KE QM

Here, m = 1.007825 u and M = 7.016003 u.