First measurement ofB(E2) values from σ<Nstates of an O(6) nucleus: Gamma-ray-induced Doppler broadening studies inPt196

In a first application of the gamma-ray-induced Doppler broadening technique to a heavy mass nucleus the first absolute transition rates from a σN state in an O(6) nucleus ${(}^{196}$Pt) are obtained. The principal results concerns the 1402 keV $0^{+}$ base state of the σ=N-2 family, namely, that B(E2:[$0_3^{+}$(σ=4)-$2_1^{+}$(σ=6)])${\mathit{e}}^2$ ${\mathrm{b}}^2$. In agreement with the selection rule which forbids Δσ=2 transitions, this corresponds to at least an order-of-magnitude hindrance compared to allowed O(6) transitions and provides a critical test of the σ quantum number.