Chemical identification, heavy elements

Timokhin, S.N., Yakushev, A.B., Perelygin, V.P., Zvara, L "Chemical Identification of Element 106 by the Thermochromatographic Method". In Proceedings of the International School Seminar on Heavy Ion Physics , Dubna, 10-15 May 1993,... 

The predictions of the chemical properties of the superheavy elements discussed in Section IV make it possible to design experiments for their chemical identification should they be produced by heavy-ion bombardement. A few simple preliminary experiments have been performed, utilizing the tandem cyclotron combination at Dubna and the SuperHILAC at Berkeley. 

Fast chemical isolation procedures to study the chemical and physical properties of short-lived radioactive nuclides have a long tradition and were applied as early as 1900 by Rutherford [1] to determine the half-life of Rn. A rapid development of fast chemical separation techniques [2-7] (see Ref. [5] for an in-depth review) occurred with the discovery of nuclear fission [8]. Indeed, the discovery of new elements up to Z = 101 was accomplished by chemical means [9]. Only from there on physical methods prevailed. Nevertheless, rapid gas-phase chemistry played an important role in the claim to discovery of Rf and Db [10]. As of today, the fastest chemical separation systems allow access to the study of a-particle emitting nuclides within less than 1 s as demonstrated by the investigation of Pa with a half-life of 0.85 s [11]. Reviews on rapid chemical methods for the identification and study of short-lived nuclides from heavy element synthesis can be found in [12-22]. 

The identification of the first transuranium elements was by chemical means. In the early 1960s physical techniques were developed which allowed for detection of nuclei with lifetimes of less than one second at high sensitivity. A further improvement of the physical methods was obtained with the development of recoil separators and large area position sensitive detectors. As a prime example for such instruments, we will describe the velocity filter SHIP (Separator for Heavy-Ion reaction Products) and its detector system, which were developed at the UNILAC. The principle of separation and detection techniques used in the other laboratories is comparable. 

The expectation that superheavy elements will be detected by chemical and other identification procedures, even with these very small-cross sections, is now shifting to the heavy-ion accelerator laboratory (GSI) in Germany. There is the hope that the use of other heavy ions (including ions up to uranium) and greater beam intensities will lead to the synthesis and identification of superheavy elements. There are also several groups associated with GSI presently developing setups to detect superheavy elements using chemical separation methods similar to those described above as well as phase separations. 

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