Abstract
<jats:p> Following the isotopic bifurcation observed in GQR–IX, the Gated Quantum Resonator (GQR) framework is here extended to sulfur–substituted analogues (H <jats:sub>2</jats:sub> S, D <jats:sub>2</jats:sub> S, T <jats:sub>2</jats:sub> S) within the same photosystem II (PSII) geometries. Time–domain simulations reveal systematic frequency compression relative to water while maintaining a shared field–geometry envelope. The combined isotope–chalcogen phase map exposes a universal resonance–shield boundary that separates collective from localised tunnelling modes. A new interpretation emerges: the low–medium–split frequency pattern reflects a dual-phase charging process, in which vibronic energy is absorbed, stored, and redistributed between two coherent channels prior to turnover. Transient hydronium clusters (H <jats:sub>3</jats:sub> O <jats:sup>+</jats:sup> , H <jats:sub>5</jats:sub> O <jats:sup>+2</jats:sup> ) act as heavy–proton mimics, bridging isotopic and chalcogenic effects under a single quantum–critical law. Together these findings show that PSII catalysis operates at a tunable boundary where mass and polarizability co-regulate tunnelling, unifying the principal schools of catalytic theory within one Hamiltonian landscape </jats:p>