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A dedicated study of the quenching of the weak axial-vector coupling strength g A in nuclear processes has been performed by the COBRA collaboration. This investigation is driven by nuclear model calculations which show that the β-spectrum shape of the fourfold forbidden non-unique decay of 113 Cd strongly depends on the effective value of g A . Using an array of CdZnTe semiconductor detectors, 45 independent 113 Cd spectra were obtained and interpreted in the context of three nuclear models. The resulting effective mean values are g A (ISM) = 0.914 ± 0.008, g A (MQPM) = 0.910 ± 0.013 and g A (IBFM-2) = 0.955 ± 0.035. These values agree well within the determined uncertainties and deviate significantly from the free value of g A . This can be seen as a first step towards answering the long-standing question regarding quenching effects related to g A in low-energy nuclear processes.

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