Nuclear structure investigations of neutron deficient nuclei in the region Z=103 to 105

The isotopes 257,255Rf, 257,256Db, 253,252Lr have been produced in bombardments of 207,208Pb and 209Bi target nuclei with 50Ti and identified by their α-decay. New or improved decay data could be obtained. Analysis of the fine structure of the α-decay pattern of 257Rf allowed the construction of a first tentative level scheme for the daughter nucleus 253No and also the identification of a low lying high spin isomeric state, while from α-γ- coincidence measurements for 255Rf a first tentative level scheme of the daughter nucleus 251No was derived. For 257Db we found that two nuclear levels decay by α-emission and populate also different levels in the daughter nucleus 253Lr. The levels are produced by the reaction process. In bombardments of 209Bi with 50Ti at ECN*=26.4 MeV and 30.8 MeV the previously unknown isotopes 256Db and 252Lr were identified.