Understanding relaxation processes in glasses is essential for linking their microscopic dynamics to macroscopic mechanical behavior. As a liquid is cooled toward the glass-transition temperature (Tg), its relaxation dynamics separate into two distinct processes: the structural (α) relaxation, involving large-scale cooperative rearrangements, and the faster Johari-Goldstein (JG) or β relaxation, a localized motion that persists below Tg. The JG relaxation governs the residual mobility of glasses and plays a central role in phenomena such as plastic flow and crystallization. Here, the JG relaxation is investigated in high-enthalpy GeSe3 glasses using fast-scanning calorimetry. High-enthalpy glassy states are reached through two independent routes: rapid thermal quenching from the melt and X-ray irradiation of the solid glass. Both methods increase structural disorder and reveal the JG relaxation as an exothermic signal below Tg in the calorimetric traces, corresponding to the release of stored enthalpy from defect regions. Although rapidly quenched and X-ray-irradiated samples can exhibit comparable enthalpy levels, their calorimetric traces differ in shape, indicating distinct microscopic pathways to high-enthalpy states. Notably, the strength of the JG relaxation is higher in irradiated glasses than in isenthalpic glasses produced by thermal procedures, although this difference is reduced for long-irradiated glasses. These results support the view that the secondary relaxation originates from defect or loosely connected regions within the glass network. Such regions act as elementary plastic units whose number increases on increasing the enthalpy of the glass until the material yields. This work establishes X-ray irradiation as a controllable and versatile method, complementary to melt quenching, for tuning structural heterogeneity and thereby tailoring the mechanical and relaxation properties of glasses.
