Cross sections for the production of Pa, Th, and Ac isotopes in the decays of highly excited compound nuclei 221,223,225,227Pa formed in reactions featuring 20,22Ne and 24,26Mg ions

The production cross sections and excitation functions have been measured for neutron-deficient isotopes Pa, Th, and Ac isotopes featuring 122 to 132 neutrons and originating from 20,22Ne+295Tl and 24,26Mg+197Au interactions. The resulting cross sections have been compared with the predictions of the statistical model of compound-nucleus deexcitation. It has been shown that none of the methods widely used to take into account the impact of shell effects on the cross sections for the production of evaporation products is able to describe consistently the entire body of experimental data. Various approaches that take into account shell effects semiempirically and which make it possible to describe the array of data obtained in the present experiment have been considered