The Raman active CuxOy complex possesses a distinct vibrational feature at 603 cm -1 assigned to the deformational mode of the 8-membered ring of a mono(μ-oxo)dicopper intermediate (ZCuOCuZ), through comparisons of measured spectra with Raman scattering frequencies calculated via density functional theory. The rates of O2 activation of ZCuOH-containing CHA samples show two distinct kinetic regimes at low (< 673 K) and high (> 685 K) temperatures. At low temperatures, rates of O2 activation do not depend on O2 pressure, show a first-to-zeroth order kinetic dependence on H2O pressure, and exhibit a normal H2O/D2O KIE. At high temperatures, O2 activation rates increase linearly with O2 pressure, show a weak dependence on H2O pressure, and possess a normal KIE on H2O/D2O. These observations agree with a plausible mechanism in which a fraction of ZCuOH sites initially reduce to form ZCu + sites and readily bind molecular O2 to form ZCuO2 intermediates. ZCu + and ZCuO2 then react to form a ZCuO2CuZ complex. These ZCuO2CuZ intermediates undergo kinetically relevant O-O bond scission, which can be facilitated by water, to form ZCuOCuZ species and O 2-. These data, methodologies, and interpretation provide a basis to understand how Cu ions within zeolites activate O2 and evolve to form species responsible for socially-and environmentally-important oxidation chemistries. The precise identification of the active species and the development of design that increase rates and selectivities remains a challenge. These goals motivate the development of synthetic methods to prepare model Cu-zeolites with more uniform Cu structures, innovative kinetic and spectroscopic tools to probe active Cu structures, and connections between experimental data and computational models to understand these complex systems.