From the core of nuclei to the matter of neutron stars with two-photon emission

The nuclear equation of state requires rigorous bench-marking of experimentally observable properties which can be accurately calculated. One such observable is the electric polarizability of nuclear matter and its difference for an excited nuclear state. One possible way of extracting this quantity is through the second order electromagnetic process of nuclear two-photon emission occurring between low-lying $0^+$ states where a single photon transition is forbidden. The first excited state of $^{90}$Zr satisfies these conditions and has been previously observed to undergo two-photon emission. The GRIFFIN spectrometer at TRIUMF-ISAC is a powerful set-up for decay studies that has the angular sensitivity, energy resolution, and data acquisition system required to make a precision measurement of $^{90}$Zr decay using a high-activity $^{90}$Sr source. In this talk I will discuss the development of this technique with GRIFFIN using source data, and how we can extend this to radioactive beam experiments for two-photon decay.