243Am + 48Ca: A Second Look at the Rf/Db Data Set

Henderson, R A ; Moody, K J

关键词: ACTINIDES;    ALPHA DECAY;    ALPHA SPECTROMETERS;    CONTAMINATION;    CYCLOTRONS;    DECAY;    DUBNA;    DUBNIUM;    ELECTRON CAPTURE;    ELEMENT 115;    FISSION;    GENETICS;    HALF-LIFE;    NUCLEAR REACTIONS;   

DOI  :  10.2172/926012
RP-ID  :  LLNL-TR-400981
PID  :  OSTI ID: 926012
Others  :  TRN: US0802520

美国|英语

来源: SciTech Connect

【 摘 要 】

In December of 2005 a series of experiments were performed at the U400 Cyclotron at the Flerov Laboratory of Nuclear Reactions in Dubna, Russia, using the reaction {sup 243}Am ({sup 48}Ca,3n) {sup 288}115 which, after a sequence of five alpha decays, produces a long-lived ({approx}1d) fission activity that had been detected previously in experiments using the Dubna Gas Filled Recoil Separator (DGFRS). These experiments were attempts to establish the elemental identity of the fissioning species as dubnium (element 105), which in turn confirms the identity of the original parent nucleus as element 115 through genetic correlation of the subsequent alpha decays. A series of approximately 24-hour bombardments were followed by chemical separations designed to isolate the Group Four and Five chemical fractions, and then separate the Nb and Ta fractions, which are Group Five homologues of dubnium and should therefore behave chemically similar. The samples were prepared for alpha and fission measurement and counted for an extended period of time. Fission events were detected in the Ta-like fractions only, which correspond to the fission coming from either the {sup 268}Db isotope directly or long-lived electron-capture decay in {sup 268}Db followed by a short half-life fission of {sup 268}Rf. In May of 2007 the Rf and Db fractions were recounted for very long times on alpha spectrometers to look at what species remained after approximately 1.5 years of time. One of the issues to be resolved was the potential for actinide contamination of the counting samples, which might have adverse affects on the observed data from the original experiment. In the original experiment the samples had significant quantities of {beta}-{gamma} activity which made the absolute identification of the alpha activity in each sample difficult. By allowing the {beta}-{gamma} activity to decay away, it gives us the opportunity to make definitive identifications of any alpha emitting isotopes on the sample planchets.