Pre-Lab Questions to Lab 11 - Nuclear States and Models Explain how you would determine that 137Cs has a spin and parity of 7/2+ . Show that the relation between half-life and lifetime is T1/2 = τ ln2.(NOTE: Atomic and molecular physicists typically talk in terms of excited state lifetimes, $\tau$ (greek "tau") , whereas nuclear physicists prefer the term half-life, T1/2 .) Compare and contrast ionization potentials of atoms with binding energy for nucleons as a function of nucleon number.                         Ionization Energy                         Binding Energy