= Nuclear rotational spectroscopy evidence
<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.<Rotational Motion in Nuclei by Aage Niels Bohr>[p. 217, Fig. 3 caption, plutonium spectrum and one-scale comparison]{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.<Rotational Motion in Nuclei by Aage Niels Bohr>[p. 225, Fig. 9 measured levels and following discussion of Fig. 10 transition matrix elements]{ref}
Using those first two excitations gives $265.0/80.56\simeq3.28947$, 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.
Back to article page
