The even-even nucleus has ground-state spin and parity
PHYSICS · Subjective · Fermi University Physics · Quantum Mechanics · Nuclear Physics · Nuclear constituents, size and binding
The Nucleus Resolved, Ch Spin, parity and the electromagnetic moments of a nucleus
Problem
The even-even nucleus 154Sm has ground-state spin and parity Jπ=0+. An independent electromagnetic measurement, exciting the nucleus with the electric field of a passing charged particle, shows that its charge distribution in its own body-fixed frame is strongly elongated, with an intrinsic quadrupole moment Q0≈+6.6eb. Atomic-beam magnetic resonance on the ground state, however, measures a spectroscopic quadrupole moment Qsp=0. A colleague argues: "Qsp=0 is a direct measurement of the charge distribution, so 154Sm must in fact be spherical; the Coulomb-excitation result must be in error." Is this argument correct? Justify your answer using the triangle condition on the multipole order and the meaning of Qsp as an expectation value in the state m=J.