1984De07: ²⁰⁸Pb(⁵⁴Cr,n) E=290 MeV at Dubna using the U400 cyclotron. SF fragments detected with solid-state track detectors. Estimated ²⁶¹Sg T_1/2(SF)> ≈0.4 s from the absence of a noticeable spontaneous fission effect.

1984DeZO, 1984Og02, 1984Og03: ²⁶¹Sg produced by ²⁰⁸Pb(⁵⁴Cr,n) and daughter of ²⁶⁵Hs produced by ²⁰⁸Pb(⁵⁸Fe,n) E=5.5 MeV/α at Dubna USING the U400 cyclotron with a beam intensities of about 0.5×10¹³ and 3×10¹³ particles/s, respectively. 34 α events (production CROSS-section of 3 nb) and three α events (production CROSS-section of 4 pb), respectively, reported for the daughter ²⁵³Es after radiochemical separation. See ²⁶⁵Hs Adopted Levels FOR details. 1984Og03 (table 3) estimated %SF<0.5.

1984Mu17, 1987Mu15: daughter of ²⁶⁵Hs produced by ²⁰⁸Pb(⁵⁸Fe,n) E=5.02 MeV/α at GSI using the UNILAC heavy ion accelerator. In-flight separation of evaporation residues was done using SHIP (1979Mu14). See 1984Mu07 for details of the experimental set-up with an excitation energy of 18 MeV 2 in the compound system. α total of 1x10¹² particles/s were delivered over 240 hours. An approximate mass determination was done using tof information and implantation energy. α and SF events were detected by an array of seven position sensitive surface barrier detectors. The calibration uncertainty of |+15 keV estimated for 8.5 MeV |< Eα |< 10 MeV and ± 25 keV for Eα>10 MeV. Three α decay chains were observed. The parent assignments were made placing reliance on the fact that the daughter α signals could be assigned to known transitions belonging to the expected daughters. The full energy of 9.57 MeV 3 deposited for ²⁶¹Sg in the second chain, is in agreement with 8 events from experiments that were going on concurrently at the time and data reported subsequently in 1985Mu11. The half-life quoted was T_1/2=0.11 s +14-4 which overlaps within uncertainties with T_1/2=0.26 s +0.11-6 from 1985Mu11. 1987Mu15 computed an estimate of randomness for the decay chains reported in 1984Mu17 of 2x10^-15, 2x10^-15 and 2x10^-14, respectively.

1985Mu11: ²⁰⁸Pb(⁵⁴Cr,n) E=257 MeV 3, 263 MeV 3, and 268 MeV 3 (beam doses of 1.3×10¹⁷, 1.6×10¹⁷, and 1.2×10¹⁷, respectively) at GSI using the UNILAC heavy ion accelerator. In-flight separation of evaporation RESIDUES was done using SHIP (1979Mu14); see 1984Mu07 for details of THE experimental set-up. Production cross-sections were 540 ps 140 (257 MeV), 80 pb +105-30 (263 MeV), and <70 pb (268 MeV). ²⁶¹Sg identified by genetic relationships. T_1/2(²⁶¹Sg)=0.26 s +11-6 and Eα=9.56 MeV 3 (9 α decays, 5 escapes, ≈60%), 9.52 MeV 3 (4 α decays, ≈27%), and 9.47 MeV 3 (2 α decays, ≈13%). Note that the unweighted average of the three groupings is Eα=9.665 MeV 3. No spontaneous FISSION events observed; %SF<10 and T_1/2(SF)>1 s estimated. Spontaneous fission is hindered by a factor of 100 when compared to the even-even ²⁶⁰Sg.

1995Ho03: ²⁰⁸Pb(⁶²Ni,n) E=5 MeV/α at GSI/SHIP in Darmstadt. α cross-section of 3.5 pb +27-18 (4 events) was measured. α total of 2.2x10¹⁸ projectile particles impinged on a 99.0% enriched Pb target. Eight targets were mounted on a wheel 310 mm in diameter rotating at 1125 rpm. EVR’s separated by velocity filter SHIP. Observed four position and time correlated chains of α particle events. Determined α energies and time intervals between successive particles. Assigned to decay of ²⁶⁹Ds by consistency of lower chain member energies and lifetimes with known Hs, Sg, Rf and No data. The measured α energies (to within |+20 keV) and emission times for the nuclei in each alpha-decay are provided.

1997Ho03 and 1997Ho13 cited by 1999Ar21, state typical results from the above data. 1995Ho03 also reported 75 α decays of ²⁶⁵Hs observed during excitation function measurements using the reaction ²⁰⁸Pb(⁵⁸Fe,n). α total of 4.4×10¹⁸ projectiles over 4 weeks of irradiation yielded a width for the excitation function of 4.8 MeV 7 with a cross-section maximum of 63 pb 10. Assignments were made by CONSISTENCY of lower chain member properties with known values. Two α-energies could be assigned to ²⁶⁵Hs: Eα1=10.310 MeV 20 and Eα2=10.578 MeV 20. It was suggested that within the statistical uncertainties both transitions decayed with a half life of 1.55 ms 20. the measurements confirmed the three decay chains reported by 1984Mu17.

1999He11: following a reanalysis of all GSI data (more than 100 events), two half-lives were reported suggesting that decays originate from two different levels. The longer half-life of 2.0 ms 3-2 was connected with decays with energy Eα=10301 keV 15 about 90% of the time and assigned to the ground state. Less intense transitions with the same half-life have energies of Eα=10426 keV 15, 10371 keV 15, and 10244 keV 15. The shorter half-life of 0.75 ms +17-12 was connected about 63% of the time with Eα=10572 keV 15 and assigned to an isomeric state. Less intense transitions with the same half-life have energies OF 10726 keV 15, 10517 keV 15, and 10336 keV 15. These transitions, however, require further experimental investigation and confirmation (2007HoZR). For the ²⁶¹Sg daughter, a careful analysis of those events FOLLOWING ²⁶⁵Hs or ^265mHs gave no hint of any significant DIFFERENCES in α-energies or half-lives.

2002Ho11: retraction of second event dated 11 November 1994 of ²⁶⁹Ds and daughters reported by 1995Ho03 following reanalysis of original data from which this sequence could not be reconstructed.

2006An13: ²⁰⁸Pb(⁵⁴Cr,n), E*=14-24 MeV at GSI/SHIP, Darmstadt. No experimental details provided. Measured excitation function; maximum production of 1.9 nb at E*=16 MeV. The authors note that that the maximum value of 1.9 nb for this 1n channel at Ex = 16 MeV exceeds more than 3 times the maximum cross-section of 0.6 nb for the 2n channel at Ex = 26 MeV. α’s, γ’s, and ce’s were also measured. ²⁶¹Sg decay showed a fine structure influenced by energy summing with ce. 107 keV γ-ray observed in coincidence with α’s and ascribed to an E2 or M1 transition. Deduced a tentative decay scheme with an indication of a g.s. |) g.s. α of 9620 keV. The uncertainty on this figure is not quoted by the experimenters.

2007HoZR: after reviewing their data on ²⁶⁵Hs presented in 1998Ho13 and 1999He11, 2007HoZR conclude that the two main transitions as GIVEN in 1998Ho13 and the interpretation given there is correct. The additional transitions mentioned in 1999He11 are based on single events or tails of the main lines and require confirmation and further experimental studies.

2007St12, 2006An13: ²⁶¹Sg produced by ²⁰⁸Pb(⁵⁴Cr,n) at GSI/SHIP, GSI, Darmstadt; transmission efficiency of SHIP was ≈40%. Measured excitation function (nine energies between 4.70- and 5.17-MeV/α). At E=4.77 MeV/α (maximum of the excitation function), α’s (PSDD detectors; 80% of 2π; FWHM=14 keV; 53% efficiency) and α-γ coincidences (Ge CLOVER detector) were measured. The method of 1984Sc13 was employed to measure the confidence level of the decay chain. α σ=2.02 nb 2 at E*=16.9 MeV 2 was measured using PbS targets. Two half-life components could be identified in reaction product (Re)-SF correlations belonging to ²⁶¹Sg and its daughter ²⁵⁷Rf. α correlation search of Re-α₁(²⁶¹Db)-α₂(²⁵⁷Lr) was performed to identify ²⁶¹Db through its α branch. α total of 11 SF events and 4 α events could be attributed to ²⁶¹Sg resulting in %ε+%B(²⁶¹Sg)=1.3 3 and %SF(²⁶¹Db)=73 29. Ten SF events could also be assigned to ²⁶¹Sg resulting in %SF(²⁶¹Sg)=0.6 2.

2009He20: daughter of ²⁶⁵Hs in experiments performed at SHIP/GSI with the reaction ²⁰⁸Pb(⁵⁸Fe,n). For experimental details see ²⁶⁵Hs adopted values. The experimenters find no evidence to support two states in ²⁶¹Sg. An α decay half life of 195 ms 15 is suggested. α decay energies are not provided.

2010Dw01 estimated mass excess of ²⁶¹Sg from systematics. The revised value after implementing SHIPTRAP data into AME evaluations is 108054 74 over 108160 30 from 2003Au03. 2021Hu06 suggest 108005 18.

2010Be16 direct production using ²⁰⁸Pb(⁵⁴Cr,nγ), beam energy of 261 MeV at LBNL. EVRs were passed though a multiwire proportional counter MWPC before being implanted into a 16x17 double sided silicon strip detector DSSD. α HPGe clover detector was mounted at the focal plane of the BGS about 5 mm away from the DSSD to measure γ rays. Eγ, ce, Eα, (recoils)(ce)(α) were measured using the DSSD. ²⁶¹Sg recoils were identified by measuring the characteristic α-decay lines in the energy range 9.2 MeV to 10.0 MeV. The half-life was measured from a total of 199 recoil α (²⁶¹Sg) events and 106 recoil-xray (²⁶¹Sg)-α (²⁵⁷Rf) correlated events. The electromagnetic decay of an isomeric state (tentatively 11/2 with an energy of less than 200 keV and a half life of about 9.0 μs) was observed for the first time in this study. The half-life of the isomer was measured from a total of 24 recoil α (²⁶¹Sg) events and 15 delayed electron recoil-xray (²⁶¹Sg)-α (²⁵⁷Rf) correlated events. The study constitutes the first observation of an electromagnetic decay of an isomeric state for a nucleus with Z>104.

2010St14: direct synthesis through the reaction ²⁰⁸Pb(⁵⁴Cr,n) using ship at GSI carried out in two parts. Excitation function MEASUREMENTS were made for ²⁶⁰Sg and ²⁶¹Sg in the first part. The second part comprised a study of ²⁶¹Sg at a beam energy of 258 MeV corresponding to the energy maximum measured in part one. Identification of isotopes was done by time-position correlations for delayed coincidences between implantation and ER and α-decays within specified time and position windows. Stringent criteria were applied for data collection and interpretation. γ radiations were measured using a clover detector with 4 crystals. An improved half life value of 184 ms 5 was measured. Three α decay energies are proposed: 9410 keV 10, 9420 keV 10 and 9550 keV 10. The last two energies represent the sum of α decay and electron conversion. No intensities or HF are provided for these and they do not feature in the tentative decay scheme. Two SF components were identified: the half life of 0.15 s +20-5 from 10 events was consistent with that of ²⁶¹Sg derived from Er-α correlations. The longer half LIFE of 4.3 s +19-10 from 11 events was attributed to ²⁶¹Db as the ε decay daughter of ²⁶¹Sg; %ε+%B(²⁶¹Sg)=1.3 3 and %SF(²⁶¹Sg)=0.6 2 which is consistent with 2007St12. α tentative decay scheme is suggested with a single g.s. to g.s. α decay energy of 9410 keV.

2011Sa41: as α decay daughter of ²⁶⁵Hs produced using the reaction ²⁰⁸Pb(⁵⁸Fe,xn) at RIKEN with GARIS. For experimental details see ²⁶⁵Hs adopted levels. α particle energies for ²⁶¹Sg ranged from 9.36 to 9.65 MeV. α half life of 150 ms +30-20 was measured. Decay properties of daughter ²⁵⁷Rf are in agreement with literature values. Authors cite 1997He29 stating that the isomeric state in ²⁵⁷Rf is not FED by via α decay from ²⁶¹Sg.

Theory: see Nuclear Science References

Assignment: ²⁰⁸Pb(⁵⁴Cr,n) E=258 MeV (2010St14), ²⁰⁸Pb(⁵⁴Cr,n) E=4.70-5.17-MeV/α (2007St12), ²⁰⁸Pb(⁵⁴Cr,n) E=261 MeV (2010Be16).