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Aage Bohr developed a description connecting individual nucleon motion with collective nuclear rotational bands and changes of nuclear shape. A deformed atomic nucleus has an intrinsic orientation, while its laboratory quantum states have definite total angular momentum. Quantizing the collective orientation produces sequences of excited levels, or nuclear rotational bands. Their energies and electric quadrupole transitions supply complementary tests of the connection between the intrinsic shape and the observed spectrum.^[ref]

A physicist.^[ref]

Aage Niels Bohr's 1975 lecture presents a plutonium ${}^{238}\mathrm{Pu}$ spectrum deduced from the fine structure of alpha decay of curium ${}^{242}\mathrm{Cm}$. The readout was decay-line energy; the comparison fixed the rotor scale from the first excitation and tested the remaining levels against $I(I+1)$. The lecture reports spectroscopy, rather than a laboratory setup operated by its author.^[ref]

His measured erbium ${}^{166}\mathrm{Er}$ $K=0$ band has excitation energies $0$, $80.56$, $265.0$, $545.4$ and $911.2\mathrm{keV}$ for $I=0,2,4,6,8$. The same lecture analyzes interband electric quadrupole transitions, adding tests beyond level positions.^[ref]

Using those first two excitations gives $265.0/80.56\simeq 3.28947$, close to the ideal $10/3$, and distinct from the ideal harmonic value $2$. Fixing the rotor scale with $80.56\mathrm{keV}$ predicts $268.53\mathrm{keV}$ at $I=4$ and $563.92\mathrm{keV}$ at $I=6$. The measured values lie about $1.32\%$ and $3.28\%$ below these predictions. This is a useful limit of the simple model: the pattern supports a rotational interpretation while revealing departures from constant inertia. It does not by itself determine a unique nuclear charge distribution. Reconstructing a level scheme also requires assigning which transitions connect which states; raw peak positions alone do not provide all spins, parities or transition strengths.