Observation of the Sign of the Nuclear Quadrupole Interaction byβ−γDirectional Correlations

We have demonstrated for the first time the possibility of determining the sign of the nuclear quadrupole interaction by $\beta -\gamma$ directional correlations in a noncubic single crystal. A simple time-differential measurement on the 828-keV level of ${}_{}{}^{115}{}_{}{}^{}\mathrm{In}$ populated by the allowed (Gamow-Teller) $\beta$ decay of ${}_{}{}^{115}{}_{}{}^{}\mathrm{Cd}$ yields the value of the quadrupole interaction of this level in a single crystal of Cd metal to be $\frac{e^2\mathrm{qQ}}{h}=+146\mathrm{}\left(5\right)\mathrm{}$ MHz.