Nuclear Data Sheets for A=268,272,276,280,284,288,292

Abstract

Spectroscopic information such as production, identification, half-lives, decay modes and possible excited states for experimentally known nuclides of mass numbers 268, 272, 276, 280, 284, 288, and 292 are presented together with the recommended values, superseding information and data in the previous ENSDF and NDS evaluation by 2005Gu33. No nuclides have yet been identified for A=296 and 300. In the last 14 years, large amounts of new and definitive data on the superheavy nuclides (SHN) have become available, thus changing almost entirely the landscape of nuclear data in this mass region, as also indicated by a number of recent review articles: 2017Og01, 2016Ho09, 2016Ho06 (for fission barriers), 2016Fo10, 2015Og05, 2015Og07, and 2013Th02. See 2003Ka71 and 2001Ka70 for IUPAC technical discussions about the discovery of Z=111 (Rg) and 2009Ba62 for discovery of Z=112(Cn), 2011Ba54 for discovery of Z=114 (Fl) and Z=116 (Lv) and 2016Ka49 for discovery of Z=113 (Nh) and Z=115 (Mc). A special issue of Nuclear Physics A444 (2015) is devoted to research on superheavy elements (SHE) with 27 articles. In particular, see article by 2015Ko20 on mass spectrometric searches for superheavy elements in terrestrial matter. See also Proceedings of Nobel Symposium NS160 ‘Chemistry and Physics of Heavy and Superheavy Elements’ published in Eur. Phys. Jour. Web of Conferences 131 (2016), in particular 2016UtZZ, 2016DmZZ and 2016HoZY.A=268: 268Db, 268Hs and 268Mt are the only experimentally identified nuclides with A=268.A=272: 272Bh and 272Rg are the only experimentally identified nuclides with A=272. A tentative level scheme for 272Bh has been proposed from the decay of 276Mt. Search for 272Ds in 235U(40Ar,3n),E=5.1-5.4 MeV/nucleon reaction and subsequent α decays at GSI (1990Sc11) proved negative with σ<0.8nb.A=276: 276Mt is the only experimentally identified nuclide with A=276. A tentative level scheme has been proposed for this nuclide.A=280: 280Rg is the only experimentally identified nuclide with A=280. A tentative evidence is reported (2017Ka66) for 280Ds, based on one possible α-α-α correlated event at RIKEN.A=284: 284Cn, 284Nh and 284Fl are the only experimentally identified nuclides with A=284. First measurement of mass/charge (A/q) ratio has been made by 2018Ga34, resulting in the determination of A=284 for 284Nh.A=288: 288Fl and 288Mc are the only experimentally identified nuclides with A=288. Two independent experiments, first by Dubna-Livermore-ORNL collaboration using DGFRS at FLNR-JINR-Dubna (2004Og07,2004Og12), and the second at GSI using TASCA (2010Du06,2011Ga19) have confirmed the existence of 288Fl and 288Mc; and a third experiment at LBNL-Berkeley using BGS (2015Ga24) further confirmed the existence of 288Mc. Chemistry-related experiments for 288Fl have been reported by 2014Ya33 and 2010Ei01. First measurement of mass/charge (A/q) ratio has been made by 2018Ga34, resulting in the determination of A=288 for 288Mc. Search for 288Ds in natural Pt, Pb and Bi samples (2011De21) using accelerator mass spectroscopy (AMS) proved negative, with extremely low upper limits established.A=292: 292Lv is the only experimentally identified nuclide with A=292. Two independent experiments, one by Dubna-Livermore collaboration (2004Og12,2004OgZZ), and the other at GSI-SHIP facility (2012Ho12) confirm the identification of 292Lv, with the assignment of ten correlated events composed of Evaporation Residues (EVR)-α1-α2-SF correlated decay chains. Search for 292Rg in natural gold materials (2011De03), and for 292Ds and 292Fl in natural Pt, Pb and Bi samples (2011De21) using accelerator mass spectroscopy (AMS) proved negative, with extremely low upper limits established. 2010Ma03 proposed the existence of a very long-lived isomer in 122292 in their search of superheavy elements in natural Th sample using inductively-coupled plasma sector field mass spectroscopy, and interpreted the observed events as due to high-spin isomers of superdeformed or hyperdeformed character. This claim, however, for other nuclides in the superheavy element region has not been verified, for example in the AMS studies of natural samples such as Pt, Os, Au, Pb and Bi by 2011De21 and 2011De03. See also the publications of the Joint Working Party (JWP) of the IUPAC-IUPAP with critical appraisal of studies dealing with search of superheavy elements in natural samples. Specifically, for A=292, 2011De21 and 2011De21, using AMS technique, found no evidence for the existence of 292Ds, 292Rg and 292Fl in natural Pt, Pb, Bi and Au samples. See also replies to above critiques by 2009Ma19, Marinov et al., arXiv:0909.1057 (2009), and 2004MaZSA=296: Search for 296Rg in natural gold materials (2011De03), and for 296Fl and 296Mc in natural Pt, Pb and Bi samples (2011De21) using accelerator mass spectroscopy (AMS) proved negative, with extremely low upper limits established. See 2016DuZX for future prospects of discovery of elements beyond Z=118. There are no data tables for A=296.A=300: Search for 300Mc in natural Pt, Pb and Bi samples (2011De21) using accelerator mass spectroscopy (AMS) proved negative, with extremely low upper limits established. There are no data tables for A=300.