The data set composes all spectra shown in the paper "Vibronic coupling limits the use of high-lying electronic states in complex moleculesfor laser cooling". The paper aims to explore the optical cycling properties of the third electronic excited state C for CaOPh and SrOPh molecules. We find that non-adiabatic couplings between the A, B, and C states lead to substantial mixing, giving rise to vibronic states that enable additional decay pathways. As such, vibronic couplings limits the use of higher electronic states for laser cooling purposes.