The/?-decay branch of aS~ to ls~ is measured by an integral method tracing the amount of lS~ daughter activity, to be 0.46 (15)%. Samples of lS~ are wepared by on-line mass separation of 136Xe-on-tungsten transfer reaction products. The amount of isobaric ~8~ in the samples is strongly suppressed by the employed separator ion source; its directly produced fraction is derived from comparison with 177mHf activity. The properties of lutetium and hafnium release from the ion source are separately determined. With this measurement r-process nucleosynthesis is estimated to account for at most 22% of the solar 18~ abundance.
The new neutron-rich isotope 1~3Lu was produced in multinucleon transfer reactions by irradiating natw/Ta targets with 11.7 MeV/u 13GXe ions, and identified by mass separation and decay spectroscopy. The measured half-life of Z83Lu is 58 ± 4 s. The properties of the excited states of Z°SHf are discussed.Recently Kirchner et al. {I] have shown that multinucleon transfer reactions taking place between 13~Xe and tantalum/tungsten are very suitable for the production of new neutron-rich isotopes above the classical fission-product region. In [I] the new isotopes 179yb, 18ZLu and 182Lu were identified and their decay properties were studied. The aim of the present work was to search for the even more neutron-rich isotope ZO3Lu that should be also produced in multinucleon transfer reactions, and for its allowed ~-transition to a three-quasiparticle state in Z~3Hf, analogous to that observed in ZS~Hf [I].The measurements were performed using the GSI online mass separator [2] at the heavy-ion accelerator UNILAC. The ZSSLu activity was produced in reactions of a 11.7 MeV/u, 10-15 particle.nA beam of z36Xe with a target containing a sandwich array of thin natural tantalum and tungsten foils of 10 mg/cm 2 and 16 mg/cm 2 total thickness, respectively. The experimental set-up and experimental procedure were described in [I].Singles y-ray and coincidence measurements were carried out simultaneously using two Ge(Li) detectors of 7 and 30% efficiency and an energy resolution (FWHM) at 1332 keV of 1.8 and 2.0 keV, respectively. For background reduction the yrays were gated by signals from a thin plastic scintillator used as B-ray detector.The results of our "F-ray measurements are presented in Fig. I and Table I. The time analyses of B and hafnium KX-rays (see Fig. I) agree within a half-life value of T~/~ = 58 ± 4 s; the 168, 249, 1057 and 1125 keV x-transitions show a similar time dependence. The half-life, lying in * On leave
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