DOE OSTI2019
Spectroscopic information such as production, identification, half-lives, decay modes and possible excited states for experimentally known nuclides of mass numbers 266, 270, 274, 278, 282, 286, 290, 294, and 298 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=302. 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), 2015Og05, 2015Og07, 2015Mo25, 2015OgZX, 2013Th02, and 2011Og07. See 2016Ka49 for IUPAC technical discussions for the discovery of Z=117 (Ts), Z=115 (Mc), Z=113 (Nh), 2001Ka70 and 2003Ka71 for Z=110-112, 2011Ba54 for Z≥113, 2009Ba62 for Z=112, and 2016Ka50 for Z=118 (Og). 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. See also 2016DuZX for future prospects of discovery of elements beyond Z=118 A=266: {sup 266}Db, {sup 266}Sg, {sup 266}Bh, {sup 266}Hs and {sup 266}Mt are the experimentally identified nuclides with A=266. Identification of {sup 266}Lr from α decay of {sup 270}Db has been proposed by 2014Kh04 from experiments at GSI, but complete details and analyses of all the four decay chains reported in this experiment have not yet been published, and discussion in 2015Og05 review article considering their work from Dubna (2013Og04, 2011Og04) and from GSI (2014Kh04) still concluded that {sup 270}Db decayed dominantly by SF mode, in contrast with dominant α decay mode proposed by 2014Kh04. Experiments carried out at FLNR-JINR-Dubna in collaboration with LLNL and ORNL, GSI-SHIP facility, RIKEN, and LBNL facilities: {sup 266}Db from the α-decay of {sup 282}Nh in two correlated decay chains at Dubna; {sup 266}Sg as α-daughter of {sup 270}Hs in 12 correlated decay chains at Dubna and GSI; {sup 266}Bh in α decay of {sup 278}Nh in three correlated decay chains observed at RIKEN, and also directly with one event in {sup 249}Bk({sup 22}Ne,5n) at LBNL, and with four events in {sup 243}Am({sup 26}Mg,3n) at HIRFL-Lanzhou; {sup 266}Hs as α-daughter of {sup 270}Ds at GSI in two different experiments, six correlated decays in the first, and 25 decay chains in the second experiment, the analysis of which has not been fully reported as yet; and {sup 266}Mt directly in {sup 209}Bi({sup 58}Fe,n) reaction at GSI in two different experiments, observing three events in the first experiment and 12 events in the second, also produced in {sup 208}Pb({sup 59}Co,n) reaction at LBNL, observing five correlated decay chains. See also 2000Ho27 for discussion on {sup 266}Sg and {sup 266}Mt. A=270: {sup 270}Db, {sup 270}Bh, {sup 270}Hs, {sup 270}Mt and {sup 270}Ds are the experimentally identified nuclides with A=270 are presented. Experiments carried out at FLNR-JINR-Dubna in collaboration with LLNL and ORNL, GSI-SHIP facility, and RIKEN: {sup 270}Db from the decay of {sup 294}Ts in six correlated decay chains at Dubna and GSI; {sup 270}Bh as α great-granddaughter of {sup 282}Nh in two correlated decay chains observed at Dubna; {sup 270}Hs directly in {sup 248}Cm({sup 26}Mg,4n) reaction at GSI, and in {sup 226}Ra({sup 48}Ca,4n) reaction at Dubna; {sup 270}Mt as granddaughter of {sup 278}Ts in three correlated decay chains at RIKEN; and {sup 270}Ds directly in {sup 207}Pb({sup 64}Ni,n) at GSI in 33 correlated decay chains. A=274: {sup 274}Bh, {sup 274}Mt and {sup 274}Rg are the experimentally identified nuclides with A=274. Search for {sup 274}Ds in {sup 238}U({sup 40}Ar, 4n),E=5.7 MeV/nucleon reaction and subsequent α decays at GSI (1990Sc11) proved negative. Experiments carried out at FLNR-JINR-Dubna in collaboration with LLNL and ORNL, GSI-SHIP facility, and RIKEN: {sup 274}Bh from the decay of {sup 294}Ts in six correlated decay chains at Dubna and GSI, {sup 274}Mt produced as α daughter of {sup 282}Nh in two correlated decay chains observed at Dubna, and {sup 274}Rg as α daughter of {sup 278}Nh produced in three correlated decay chains at RIKEN. A=278: {sup 278}Mt, {sup 278}Rg and {sup 278}Nh are the experimentally identified nuclides with A=278. A very tentative evidence is provided for {sup 278}Bh and {sup 278}Hs from a chain originally observed and assigned to {sup 289}Fl by 1999Og10, but later reassigned by 2004Og10 to {sup 290}Fl, and further discussed in detail by 2016Ho09, where, based on systematics of α decays and SF half-lives, {sup 290}Fl is proposed to decay via ε mode to {sup 290}Nh, which then decays by an α chain, ending in {sup 278}Bh that decays by SF mode. Experiments carried out at FLNR-JINR-Dubna in collaboration with LLNL and ORNL labs in the USA, GSI-SHIP facility, and RIKEN: {sup 278}Mt from the decay of {sup 294}Ts in six correlated decay chains at Dubna and GSI, {sup 278}Rg produced as α daughter of {sup 282}Nh in two correlated decay chains observed at Dubna, and {sup 278}Nh produced directly in three correlated decay chains at RIKEN. A=282: {sup 282}Rg, {sup 282}Cn and {sup 282}Nh are the experimentally identified nuclides with A=282. A very tentative evidence is provided for {sup 282}Mt and {sup 282}Ds from a chain originally observed and assigned to {sup 289}Fl by 1999Og10, but later reassigned by 2004Og10 to {sup 290}Fl, and further discussed in detail by 2016Ho09, where, based on systematics of α decays and SF half-lives, {sup 290}Fl is proposed to decay via ε mode to {sup 290}Nh, which then decays by an α chain, ending in {sup 278}Bh that decays by SF mode. Experiments carried out at FLNR-Dubna, in collaboration with LLNL and ORNL labs in the USA, and at GSI-SHIP facility confirm the identification of these isotopes, {sup 282}Rg in α decay chain of {sup 294}Ts in six correlated decay chains at Dubna and GSI, {sup 282}Cn produced in four ways at Dubna: independently in one correlated decay chain, as α daughter of {sup 286}Lv in 11 correlated decay chains, as α grand-daughter of {sup 290}Lv in 12 correlated decay chains, as α great-grand daughter of {sup 294}Og in four correlated decay chains, and {sup 282}Nh produced at Dubna directly in two correlated decay chains. A=286: {sup 286}Nh and {sup 286}Fl are the only experimentally identified nuclides with A=286. A very tentative evidence is provided for {sup 286}Rg and {sup 286}Cn from a chain originally observed and assigned to {sup 289}Fl by 1999Og10, but later reassigned by 2004Og10 to {sup 290}Fl, and further discussed in detail by 2016Ho09, where, based on systematics of α decays and SF half-lives, {sup 290}Fl is proposed to decay via ε mode to {sup 290}Nh, which then decays by an α chain, ending in {sup 278}Bh that decays by SF mode. 2017Ka66 in experiments at RIKEN using GARIS separator interpret one correlated decay chain in three different ways, one involving possible production of {sup 294}Lv in {sup 248}Cm({sup 48}Ca,2n),E=261.6 MeV, and α decay to {sup 290}Fl which further decays to {sup 286}Cn. Experiments carried out at FLNR-Dubna, in collaboration with LLNL and ORNL labs in the USA, and at GSI-SHIP facility confirm the identification of these isotopes, {sup 286}Nh as α grand-daughter of {sup 294}Ts in six correlated decay chains, and {sup 286}Fl produced in three ways: independently in 11 correlated decay chains, as α daughter of {sup 290}Lv in 12 correlated decay chains, and as α grand-daughter of {sup 294}Og in four correlated decay chains. A=290: {sup 290}Mc and {sup 290}Lv are the only experimentally identified nuclides with A=290. A tentative evidence is provided for {sup 290}Nh and {sup 290}Fl from a chain originally observed and assigned to {sup 289}Fl by 1999Og10, but later reassigned by 2004Og10 to {sup 290}Fl, and further discussed in detail by 2016Ho09, where, based on systematics of α decays and SF half-lives, {sup 290}Fl is proposed to decay via ε mode to {sup 290}Nh, which then decays by an α chain, ending in {sup 278}Bh that decays by SF mode. 2017Ka66 in experiments at RIKEN using GARIS separator interpret one correlated decay chain in three different ways, one involving possible production of {sup 294}Lv in {sup 248}Cm({sup 48}Ca,2n),E=261.6 MeV, and α decay to {sup 290}Fl. Experiments carried out at FLNR-Dubna, in collaboration with LLNL and ORNL labs in the USA, and at GSI-SHIP facility confirm the identification of these isotopes, {sup 290}Mc as α daughter of {sup 294}Ts in six correlated decay chains, and {sup 290}Lv produced in two ways, independently in 14 correlated decay chains, and as α daughter of {sup 294}Og in four correlated decay chains. A=294: {sup 294}Ts and {sup 294}Og are the only experimentally identified nuclides with A=294. Experiments carried out at FLNR-Dubna, in collaboration with LLNL and ORNL labs in the USA, and at GSI-SHIP facility confirm the identification of these isotopes, with a total of six EVR-α-SF correlated decay chains observed for {sup 294}Ts and four for {sup 294}Og. Tentative identification of {sup 294}Lv is provided by 2017Ka66 from the observation one correlated event using GARIS-RIKEN facility, where this event is interpreted in three possible ways, two interpretations lead to production of {sup 293}Lv and successive odd-A nuclides of {sup 289}Fl, {sup 285}Cn and {sup 281}Ds, whereas the third prediction starts with the production of {sup 294}Lv and successive {sup 290}Fl and {sup 286}Cn nuclides. Search for {sup 294}Rg in natural gold materials (2011De03), and for {sup 294}Ds, {sup 294}Fl and {sup 294}Mc in natural Pt, Pb and Bi samples (2011De21) using accelerator mass spectroscopy (AMS) proved negative, with extremely low upper limits established. Also 1980St05 did not see any evidence for {sup 294}Ds in natural Pt sample using AMS. A=298: Search for {sup 298}120 through fusion-evaporation reaction at Dubna, and for {sup 298}Fl and {sup 298}Mc in natural Pt, Pb and Bi samples using accelerator mass spectroscopy (AMS) proved negative. Tentative assignment of three α-α-α decay chains by 2016Ho09 to {sup 299}120 in {sup 248}Cm({sup 54}Cr,3n){sup 299}120 at GSI was refuted by 2017He11, assigning these correlations to random events, instead. A=302: Fluorescent x rays from Z=120 element were observed by 2012Fr03 from compound nucleus {sup 302}120 produced in {sup 238}U({sup 64}Ni,X),E=6.6 MeV/nucleon at GANIL, and x-ray yields were measured, together with minimum average time deduced from x-ray multiplicity. The compound nucleus could decay by 3n- or 4n-channels to produce {sup 299}120 or {sup 298}120. 2012He05 and 2016Ho09 also produced {sup 302}120 compound nucleus in {sup 248}Cm({sup 54}Cr, xn){sup 302}120{sup *},E=6.035 MeV/nucleon; and {sup 238}U({sup 64}Ni,xn){sup 302}120{sup *},E=5.53 MeV/nucleon reactions using UNILAC at GSI. Three α-α-α correlated decays from {sup 248}Cm({sup 54}Cr,xn){sup 302}120{sup *} reaction were tentatively assigned by 2016Ho09 to {sup 299}120 decay, however, a detailed analysis by 2017He11 refuted this claim, ascribing these events to random sequences. There are no data tables for A=302.
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