Synthesis of rutherfordium isotopes in the U238(Mg26, xn)264-xRf reaction and study of their decay properties

Isotopes of rutherfordium (Rf258-261) were produced in irradiations of U238 targets with Mg26 beams. Excitation functions were measured for the 4n,5n, and 6n exit channels. Production of Rf261 in the 3n exit channel with a cross section of 28_-26⁺⁹² pb was observed. α-decay of Rf258 was observed for the first time with an α-particle energy of 9.05 ± 0.03 MeV and an α/total-decay branching ratio of 0.31 ± 0.11. In Rf259, the electron capture/total-decay branching ratio was measured to be 0.15±0.04. The measured half-lives for Rf258, Rf259, and Rf260 were 14.7_-1.0^+1.2 ms, 2.5_-0.3^+0.4 s, and 22.2_-2.4^+3.0 ms, respectively, in agreement with literature data. The systematics of the α-decay Q-values and of the partial spontaneous fission half-lives were evaluated for even-even nuclides in the region of the N=152,Z=100 deformed shell. The influence of the N=152 shell on the α-decay Q-values for rutherfordium was observed to be similar to that of the lighter elements (96⩽Z⩽102). However, the N=152 shell does not stabilize the rutherfordium isotopes against spontaneous fission, as it does in the lighter elements (96⩽Z⩽102).