Formation of high spin isomers Fe-52m and Fe-53m in He-3-particle induced nuclear reactions on Cr-52

Excitation functions were measured for the formation of high spin isomers Fe-52m (J = 12(+)) and Fe-53m (J = 19/2(-)) from threshold to 36 MeV in the interactions of He-3-particles with Cr-nat. Use was made of the activation technique in combination with high-resolution gamma-ray spectroscopy. Thin samples were prepared by electrolytic deposition of Cr-nat on Au-backing. Measurements on the short-lived Fe-52m (T-1/2 = 45.9 s) could be done only after a fast radiochemical separation via solvent extraction. From the available experimental data the isomeric cross-section ratios sigma(m)/(sigma(m) + sigma(m)) for the formation of the isomeric pairs Fe-52m,Fe-g and Fe-53m,Fe-g in Cr-52(He-3,3n) and Cr-52(He-3,2n) processes, respectively, were deduced. Over the investigated energy range the maximum values of the ratios amount only to 0.05 and 0.12, respectively. The low probabilities of formation of the isomeric states are attributed to their high spins.