The conversion electron spectrum following alpha decay of ${\mathrm{Am}}^{241}$ has been reinvestigated with 180° focusing beta-ray spectrographs at ∼0.1% resolution. Multipolarity assignments for several gamma transitions are made, principally on the basis of relative $L$-subshell conversion coefficients. Energy-level spacings and relative transition probabilities are compared and discussed in terms of the Bohr-Mottelson model. The excellent agreement of energy-level spacings with the rotational formula and the general pattern of radiative transitions firmly establish the essentially rotational nature of these bands of levels. However, calculations involving $M1\mathrm{}$ transition probabilities and magnetic moments lead to discrepancies with the simple theory in the case of the ground rotational band.

• Received 23 February 1956

DOI:https://doi.org/10.1103/PhysRev.102.1372