Alpha decay of giant resonances of sup(58,60)Ni nuclei

The cross sections of the sup(58, 60)Ni(e, e' p) and sup(58, 60)Ni(e, e'α) reactions are measured in the electron energy range 12-35 MeV. The experimental results have been analyzed using the DWBA virtual photon spectra. At energies Esub(γ)=16.0+-1.0 MeV for 58Ni and Esub(γ)=15.6+-1.0 MeV for 60Ni giant electric quadrupole resonances which decay predominantly via the α-particle emission have been observed. The integral cross sections of the reactions 58Ni(γ, α) and 60Ni(γ, α) due to E2-transitions equal 5.4+-1.4 and 6.0+-3.0 mbxMeV, respectively. These values are (47+-12)% for 58Ni and (56+-28)% for H60Ni of the total strength of the isoscalar E2-transitions. The integral cross sections of the same reactions due to E1-transitions are 15.9+-2.3 and 16.9+-4.8 mbxMeV, i.e. (1.7+-0.3)% for 58Ni and (1.8+-0.5)% for 60Ni of the values given by the electric dipole sum rules. The measured integral cross sections of the sup(58, 60)Ni(γ, p) reactions equal 539+-33 and 300+-20 mbxMeV