Past exam of the particle and nuclear physics course of the University of Cambridge / 2014 / Paper 1 / 4 / b / ii / Solution

For comparable transition energies and ordinary single-particle nuclear strengths in the long-wavelength regime, the usual qualitative ordering is $E1$, $M1$, $E2$, $M2$, $E3$, $M3$ from faster to slower. Each increase of multipole order is strongly suppressed, and magnetic radiation is usually weaker than electric radiation of the same order. More precisely,The nuclear reduced transition strength $B$ is essential: collective enhancement, cancellation and selection rules can overturn this benchmark. It is not a universal ranking between arbitrary transitions of different energies. The weak measured M3 branch is consistent with high-multipole suppression, but its absolute lifetime cannot be obtained from its arbitrary-unit intensity alone.^[ref]