Probing the isospin mixing in the ⁷²Kr compound nucleus via GDR <italic>&#947;</italic> decay

The isospin mixing was deduced in the compound nucleus ⁷²Kr at a low nuclear temperature around 1.3 MeV, from the γ decay of the giant dipole resonance. The γ rays from two compound-nucleus reactions were measured: from the ³² S + ⁴⁰Ca at bombarding energy of 90 MeV characterized by isospin I = 0, and from the ³¹ P + ⁴⁰Ca at 82 MeV used as a reference. The ELIFANT array was employed at the Bucharest Tandem Laboratory, consisting of Compton-suppressed scintillator detectors. The statistical-model analysis of the measured spectra provided a mixing parameter of (3.5±0.8)%. This new point, being at the lowest temperature compared with the few other existing ones, can validate the predictions of the temperature dependence of the isospin mixing. The isospin-symmetry-breaking correction, δc, used for the Fermi super-allowed transitions was extracted from the present result of the isospin mixing and found to be consistent with β decay data, theoretical predictions, and previous experimental results.