"Chemical characterization of element 112" R.Eichler et al. Nature Vol 447,May 2007

"The results of this study are of characteristically high quality but there is insufficient internal redundancy to warrant conviction at this stage. Confirmation by further results is needed to assign priority of discovery to this collaboration." 

S. Hofmann, V. Ninov, F. P. Hessberger, P. Armbruster, H. Folger, G. Munzenberg, H. J. Schott, A. G. Popeko, A. V. Yeremin, S. Saro, R. Janik, M. Leino. "The new element 112", Z. Phys. A 354, 229230 (1996).

Using the electromagnetic velocity filter SHIP, fusion-like residues of the reaction of ⁷⁰Zn with enriched ²⁰⁸Pb targets were measured. Two chains of localized alpha-emitters were identified as originating with ²⁷⁷112. The quality of the data is very high. However, regarding the complete criteria, there is only one incidence of redundancy, that assigned to the previously uncharacterized isotope ²⁶⁹Hs that appears in both events; there is no redundancy involving known daughters. The observed alpha leads to the known isotope ²⁶⁵Sg, but then reports a ²⁶¹Rf alpha energy that is in significant disagreement with known energies, posing uncertainty with the assignment. The last alpha in the chain agrees extremely well with that of descendant ²⁵⁷No, but is the only concordant daughter comparison event of the entire 112 set. 
 

Y. A. Lazarev, Y. V. Lobanov, Y. T. Oganessian, V. K. Utyonkov, F. S. Abdullin, A. N. Polyakov, J. Rigol, I. V. Shirokovsky, Y. S. Tsyganov, S. Iliev, V. G. Subbotin, A. M. Sukhov, G. V. Buklanov, B. N. Gikal, V. B. Kutner, A. N. Mezentsev K. Subotic, J. F. Wild, R. W. Lougheed, K. J. Moody. "- Decay of ²⁷³110: Shell closure at N=162" , Phys. Rev. C 54, 620624 (1996).

Reference reports its ²⁷³Ds alpha particle with energy 11.35 MeV in agreement with this Hofmann et al. groups 11.45 MeV when resolution is taken into account. There are other chains in this reference noted with less confidence, but that nevertheless do not provide further redundancy to these results by Hofmann et al.

The Hofmann et al. collaboration reports on one new chain originating from ²⁷⁸112 in the ⁷⁰Zn + ²⁰⁸Pb reaction. However, re-analysis of the previous report two chains was unable to confirm the original results for the first chain as noted above. Hofmann et al. thus have a total of two alpha and lifetime chains of events originating with the new isotope ²⁷⁷112 leading to two alpha and lifetime events of ²⁷³Ds, in good agreement with a single observation assigned to ²⁷³Ds by Lazarev et al.  in their tenuous chain. The chains continue to the previously unknown ²⁶⁹Hs for which alpha energies and lifetimes are similar in both events. The Hofmann et al. chains continue through ²⁶⁵Sg, but with no alpha energies. The lifetimes seen are consistent with 8 s from a previous study of ²⁶⁵Sg but not with 158 s found. Only the first chain of Hofmann et al. resumes, producing ²⁶¹Rf with an 8.52 MeV alpha and 4.7 s lifetime. The alpha energy is in agreement with the literature value, but the lifetime is not. This situation is also somewhat confounded by the study of ²⁶¹Rf. Here, 8.30 MeV (but no 8.52 MeV) alpha particles are observed for which the lifetime is acknowledged to be 78 s. As mentioned previously, the first ²⁷⁷112 chain ultimately decays through an alpha and lifetime in very good agreement with that for the known isotope ²⁵⁷No. In summary, though, there are only two chains, and neither is completely characterized on its own merit. Supportive, independent results on intermediates remain less than completely compelling at this stage.
 

The collaborations of Oganessian et al. used the reactions ⁴⁸Ca + ²⁴²Pu and ⁴⁸Ca + ²⁴⁴Pu, respectively, each to make one observed chain originating with ²⁸⁷114 and ²⁸⁹114, respectively, which pass through unknown intermediates terminating in spontaneous fission.
 

The Dubna collaboration of Oganessian et al. used the reaction ⁴⁸Ca + ²³⁸U to make ²⁸³112 in which the two events decay by spontaneous fission with a lifetime of ~2 min. An independent repeat of the © 2003 IUPAC, Pure and Applied Chemistry 75, 16011611 On the claims for discovery of elements 110, 111, 112, 114, 116, and 118 1605 same experiment, however, did not lead to any events nor did another independent attempt to follow the eka-Hg chemistry of element 112 produced by the same path lead to any events.

 W. Loveland, K. E. Gregorich, J. B. Patin, D. Peterson, C. Rouki, P. M. Zielinski, K. Aleklett. Search for the production of element 112 in the ⁴⁸ Ca + ²³⁸ U reaction, Phys. Rev. C 66, 044617-1-5 (2002).

A. B. Yakushev, G. V. Bulkanov, M. L. Chelnokov, V. I. Chepigin, S. N. Dmitriev, V. A.Gorshkov, S. Hübener, V. Ya. Lebedev, O. N. Malyshev, Yu. Ts. Oganessian. First attempt to chemically identify element 112, Radiochim. Acta 89, 743 (2001).

The Oganessian et al. collaborations, in which ²⁴⁴Pu + ⁴⁸Ca in the first and ²⁴⁸Cm + ⁴⁸Ca in the second case are used to produce decay chains commencing with ²⁸⁸114 or ²⁹²116, respectively, followed by a pair of well-reproduced ±-decays assigned to the otherwise unknown ²⁸⁴112 and terminating in spontaneous fission of previously unknown ²⁸⁰Ds. The decay energies and lifetimes of three events for ²⁸⁴112 are internally redundant, but no link to recognized nuclei occurs. In the ²⁴⁴Pu + ⁴⁸Ca study, another event originating with ²⁸⁹114 followed by a chain observed through ²⁸⁵112 and ²⁸¹Ds terminates with spontaneous fission at ²⁷⁷108, all previously unknown. The Dubna collaborations have performed careful, high-quality studies whose acknowledgement as discoveries is unfortunately not yet warranted because of unsecured connection to known descendents and unobserved elemental signatures (such as well-resolved X-ray energies).

Yu. Ts. Oganessian, V. K. Utyonkov, K. J. Moody. "Synthesis of ²⁹²116 in the ²⁴⁸Cm + ⁴⁸Ca reaction¡", Phys. Atom. Nucl. 64, 1349¨C1355 (2001). 

Yu. Ts. Oganessian, V. K. Utyonkov, Yu. V. Lobanov, F. Sh. Abdullin, A. N. Polyakov, 
I. V. Shirokovsky, Yu. S. Tsyganov, G. G. Gulbekian, S. L. Bogomolov, B. N. Gikal, A. N. 
Mezentsev, S. Iliev, V. G. Subbotin, A. M. Sukhov, O. V. Ivanov, G. V. Buklanov, K. 
Subotic, M. G. Itkis, K. J. Moody, J. F. Wild, N. J. Stoyer, M. A. Stoyer, R. W. Lougheed, 
C. A. Laue, Ye. A. Karelin, A. N. Tatarinov. "Observation of the decay of 262116", Phys. Rev. C 63, 011301/1¨C011301/2 (2001). 
  

This collaboration continues to press arguments favoring their discovery of element 112 through the existence of very long-lived isomeric states of actinides and transactinides, of very high fusion cross-sections for their formation, each several orders of magnitude beyond traditional understanding. As indirect evidence, their discovery of long-lived ²³⁶Bk and ²³⁶Am more than a decade ago is frequently cited in their papers, yet the several existing compendia of isotopes do not acknowledge the existence of these species. The collaboration results include mention of observing long-lived proton-decay, of deformed spallation products undergoing secondary fusion reactions, and of hyperdeformed shapes, any of which significant topics by themselves should have attracted studies by other groups years ago. Yet this has not occurred. The collaborations arguable use of forceful expressions such as "overwhelming evidence", "clear and proven", and "impossible to refute" is neither convincing nor swaying. Extraordinary intriguing phenomena, not much selective in their measured character, are, in part, necessary for the acceptance of the collaborations interpretations of their data. 

A. Marinov, S. Gelberg, D. Kolb. Abnormal radioactive decays out of long-lived superand hyper-deformed isomeric states, Proc. Intl. Symp. on Exotic Nucl. Struct. 1520 May 2000, Debrecen, Hungary, pp. 341344 (2000).

A. Marinov, S. Gelberg, D. Kolb. Discovery of long-lived shape isomeric states which decay by strongly retarded high-energy particle radioactivity, Int. J. Mod. Phys. E 10, 185208 (2001).
   

A. Marinov, S. Gelberg, D. Kolb. Strongly enhanced low energy alpha-particle decay in heavy actinide nuclei and long-lived superdeformed and hyperdeformed isomeric states, Int. J. Mod. Phys. E 10, 209236 (2001).

A. Marinov. Isomeric states and uncharacterized a -particle groups in nature, Proc. 3 rd
Int. Conf. on Exotic Nuclei and At. Masses, 27 July, p. 380 (2001). 

For completeness, we take note of the Berkeley collaboration study of ⁸⁶Kr + ²⁰⁸Pb by Ninov et al.. Three chains terminating in ²⁶⁹Sg enabled observation of intermediate ²⁸¹112 .Retraction of results appear in:

V. Ninov, K. E. Gregorich, W. Loveland, A. Ghiorso, D. C. Hoffman, D. M. Lee, H. 
Nitsche, W. J. Swiatecki, U. W. Kirbach, C. A. Laue, J. L. Adams, J. B. Patin, D. A. 
Shaughnessy, D. A. Strellis, P. A. Wilk. Editorial note: "Observation of superheavy nuclei produced in the reaction of 86Kr with ²⁰⁸Pb" [Phys. Rev. Lett. 83, 1104 (1999)], Phys. Rev. Lett. 89, 039901 (2002).

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2008-01-11