Accurate nuclear quadrupole moment values are essential as benchmarks for nuclear structure models and for the interpretation of experimentally determined nuclear quadrupole interactions in terms of electronic and molecular structure. Here, we present a novel route to such data by combining perturbed $\gamma \text{−}\gamma$ angular correlation measurements on free small linear molecules, realized for the first time within this work, with state-of-the-art ab initio electronic structure calculations of the electric field gradient at the probe site. This approach, also feasible for a series of other cases, is applied to Hg and Cd halides, resulting in $Q({}^{199}\mathrm{Hg},5/2^{-})=+0.674(17)b$ and $Q({}^{111}\mathrm{Cd},5/2^{+})=+0.664(7)b$.

Induced long-range magnetic interactions in Pd single crystals covered with ferromagnetic Ni are observed in perturbed angular correlation measurements applying monolayer-resolved sample preparation. The ${}^{100}$Pd${\mathrm{/}}^{100}$Rh probes sense magnetic interactions even seven atomic layers away from the Ni-Pd interface. The results are interpreted assuming fluctuations of magnetic moments strongly interacting with the ${}^{100}$Rh nuclei.