Chapter 18: Appendix: Implications of Superimposed Spin States

The appendix addresses a problem that can often cause confusion. Elementary quantum mechanics tells us that, prior to measurement, spin states are generally superpositions of eigenstates. However, nuclear magnetic resonance and key experiments, such as the Stern/Gerlach demonstration of space quantization, are usually described exclusively in terms of pure eigenstates. It is shown that pure eigenstate representations, on average, lead to correct results, including the validity of the conservation of energy and angular momentum.