Ben Roy Mottelson

Ben Mottelson helped connect independent-particle nuclear motion with collective excitations. In a simple positive-parity, $K=0$ ground state nuclear rotational band of an even-even nucleus, the excitation energies approximately follow $E_J={\hslash }^{2}J(J+1)/(2\mathcal{I})$ for $J=0,2,4,\dots$, where $\mathcal{I}$ is a moment of inertia. Thus $E_4/E_2=10/3$ in this idealization. Comparing such patterns and transition strengths with observation distinguishes organized collective motion from an arbitrary list of separate particle excitations.^[ref]

A physicist.^[ref]