Probability of isospin mixing at high excitation has been determined only for few nuclei. Thus, we attempted to extract the degree of isospin mixing in several light, self-conjugate compound nuclei at excitation energy around 50 MeV and study its dependence on atomic mass number. For this purpose we have studied the statistical decay of the Giant Dipole Resonance (GDR) built on excited states formed in heavy-ion fusion reactions. We have measured the ²⁰Ne + ¹²C, ¹²C + ²⁴Mg, ²⁰Ne + ²⁴Mg and ³⁶Ar + ²⁴Mg reactions populating N = Z compound nuclei: ³²S, ³⁶Ar, ⁴⁴Ti, ⁶⁰Zn and the ¹⁹F + ¹²C, ¹²C + ²⁵Mg, ²⁰Ne + ²⁵Mg and ³⁶Ar + ²⁵Mg reactions populating neighbouring compound nuclei with N \not =Z at close excitation energy (temperature). Heavy-ion beams from the Warsaw Cyclotron have been used. High-energy \gamma -rays emitted in the reactions have been measured with the JANOSIK set-up. Measured spectra have been fitted with the CASCADE statistical model calculations assuming a Lorentzian GDR strength function.

PACS numbers: 24.30.Cz, 25.70.--z, 23.20.--g