Evidence for the formation of sodium hassate(VIII)

Abstract

Element 108 / Hassium / Volatile HsO 4 / In-situ production / Adsorption on hydroxide / CALLISTO Summary. Hassium, element 108, was produced in the fusion reaction between 26 Mg and 248 Cm. The hassium recoils were oxidized in-situ to a highly volatile oxide, presumably HsO 4 , and were transported in a mixture of He and O 2 to a deposition and detection system. The latter consisted of 16 silicon PIN-photodiodes facing a layer of NaOH, which served, in the presence of a certain partial pressure of water in the transport gas, as reactive surface for the deposition of the volatile tetroxides. Six correlated α-decay chains of Hs were detected in the first 5 detectors centred around detection position 3. In analogy to OsO 4 , which forms Na 2 [OsO 4 (OH) 2 ], an osmate(VIII), with aqueous NaOH, HsO 4 presumably was deposited as Na 2 [HsO 4 (OH) 2 ], a hassate(VIII).

Chemistry of superheavy elements

“…This gas mixture transported HsO 4 and simultaneously produced OsO 4 to a linear array of 12 detectors (PIN-diodes) facing a stainless steel plate coated with a thin film of NaOH. From the adsorption pattern of HsO 4 and OsO 4 at the beginning of the chemically reactive NaOH surface, presumably forming Na 2 [HsO 4 (OH) 2 ] in analogy to the know osmate (VIII), it was concluded that HsO 4 and OsO 4 show a similar reactivity in this first acid-base reaction with HsO 4 [155]. This is in agreement with a theoretical calculation [230].…”

“…Over the last decades, in addition to the above mentioned techniques and devices, several very unique detection systems for highly volatile or gaseous products were developed; among them a cryo-detector [154] for the search for SHE, CALLISTO [155] for a study of HsO 4 interacting from the gas phase with solid sodium hydroxide, OSCAR [156] for a search for 272 Hs, and a combination of ionization chamber and neutron-multiplicity detector in an experiment to search for element 112 [157].…”

“…Like its lighter homologs Ru and Os, it is expected to show a property which is unique among all transition metals: formation of a highly volatile tetroxide MO 4 (M = Hs, Os, Ru) while exploiting the highest possible oxidation state (8+). All successful Hs chemistry experiments used HsO 4 , explored its volatility [81] and reactivity [155], and exploited its volatility in nuclear synthesis and decay studies [78,227] with unprecedented sensitivities. This gave access to new and interesting Hs isotopes -doubly-magic, deformed 270 Hs [72] and 271 Hs [80] formed in a 3n-evaporation channel -and their Sg and Rf daughter nuclides [78,215].…”

“…A different type of Hs experiment [155] was performed by a collaboration using a set-up dubbed CALLISTO. Also in this experiment, tetroxides were formed in-situ in a hot recoil chamber.…”

Aqueous-phase chemistry of the transactinides

“…Following the example of Zhuikov [141], several groups have adopted the in-situ production of volatile tetroxides directly behind the target by adding oxygen (typically 10%) to the carrier gas that contains no aerosol particles [142][143][144]. Typically, the reaction products were transported with the carrier gas through a quartz column containing a quartz wool plug heated to some 600…”