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Superheavy Element Cn (Z = 112) & Fl (Z = 114) – Interaction Using COLD Setup

P. Ionescu1,2, R. Eichler1, 2, A. Türler1

1 Department of and Biochemistry, University Bern / CH 2 Laboratory of Radiochemistry, Paul Scherrer Institute / CH Introduction

40 ● Cn & Fl of interest as the heaviest 12 ● artificial Superheavy Elements (SHE, Z > 103) 20 group 14 CnSe homologs of groups 12 & 14. 0 ● produced in fusion reactions at U-400 at JINR, Russia -20 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 ● Empirical trends in periodic table1 -40 HgSe GeSe -60

Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og (MSe) -80

3.8 s 480 ms 2 298 PbSe

H -100 ● Relativistic effects on e-shell Z > 55 f SnSe  Figure 1: The 7th showing the superheavy elements. -120 ● short half-lives in the s to μs-range -140 ● Model GC with Hg-203 FlSe CdSe -160 ZnSe ● single- chemistry -180 -200 ● Se chosen 0 50 100 150 200 250 300 350 400  chromatography (GC) is a method fast & sensitive enough 298  Allotropy plays role sublH (M) Figure 2: Trends in Groups 12 & 14 reacting with Se Experimental Off‐line On‐line GC Column Manufacture: SHE experiments are conducted in , Russia using the U-400 cyclotron. ● Se cast prepared by melting Se in quartz tube, then molding it, leaving a hollow a-Se coated column 242Pu (48Ca, 3n) 287Fl Nat.Nd (48Ca, xn) 194-197Hg ● Physical vapor deposition (PVD) done by heating a Se sample in high vacuum & depositing it on a cool surface some centimeters away

Figure 4: (Left) Fusion reactions employed to produce desired elements. (Right) SHE of interest. ● H2Se photolysis is done by preparing the gas, then decomposition using UV light leaving a thin a-Se coat on the quartz. ● SHE & tracer Hg produced in fusion reaction GC was done using Cryo On-line Detector (COLD) ● a-Se can be converted to t-Se using heat treatment ● Real-time GC monitoring in COLD in self-cleaning gas loop by α- decay of radionuclides

25 °C -160 °C t-Se Au

Figure 3: Method for evaluating GC. Hg is carried with a gas stream through a Se column. If the Hg interacts with the surface and is stuck, its γ-decay can be detected by position through a collimator. GC combined with Monte-Carlo Simulation (MCS)3 Figure 5: (Left) COLD array of 64 α-particle & “PIN” detectors. Color bar displays thermal gradient from 25 °C isothermal Se covered detectors to a thermal gradient for the Au detectors. (Right) PIN detector schematic. PIN position-time-stamped energy resolution allows the reliable identification of SHE decay chains. ● Yields adsorption enthalpy ΔHads ● distinguish between physi- and chemisorption ● PIN Detectors coated in Au, Se ● identify a-Se and t-Se surface ● Energy, time & position resolution ● No fission background = highly efficient (>80%) SHE ● Tracer 203Hg from SINQ-NS; Nat.Tl (n, pxn) 203Hg identification probability Results & Conclusion Off‐line On‐line 0.01 Mean O At 2 Mean H O Observed SHE-attributed Decays 0.06 2 Hg Mean H NormalizedNormalized Hg HgDeposition Deposition on Grey on t-Se, Se, MCMC Simulation Simulation Normalized Hg Deposition on t-Se Quartz Slides, 2 60 MC Simulation 0.001 0.05

70 50 0.04 1E-4 Hg norm Hg 60 Sim with 9% Red Se coverage MC Sim, 95% t-Se 0.03 40 1E-5 Counts per Integral

50 0.02 Gas Composition a.u.

1E-6 30 40 0.01

0.00 1E-7 30 20 30 40 20 Getter: 400 °C 950 °C Run Number 20 Figure 7: (Left) Cn events observed. Events from previous years in green. (Right) Hg & At count fluctuation throughout Normalised Counts (%) Normalised Hg Deposition 10 the successive runs in entire COLD. Relative H2, O2 & H2O levels shown. Violet circles indicate where Hg was lost in gas 10 loop. (Below) Typical normalized Hg deposition pattern in COLD, with thermal gradient in red.

50 20 0 0 ● Not all Hg is detected in COLD 12345678910 1234567891011 Hg Deposition 0 Column Distance (cm) Position (cm) 40 MC Simulation -20 ● Detector cleaning increased counts Figure 6: (Left) GC of cylindrical t-Se column, MCS shows approx. 9% a-Se coverage. (Right) GC of PVD glass slides -40

mimicking COLD geometry showing approx. 5% a-Se coverage using MCS Temp (°C) 30 -60  Au surface likely contaminated

● Adsorption enthalpy for the Se allotropes was determined to be -80 Hg Hg 20  Se detector count rate unaffected ΔHads (a-Se) < -85 kJ/mol, and ΔHads (t-Se) > -60 kJ/mol. -100

-120● Getter ↑ yield ● Inverse GC to explore kinetics of reaction Normalised Hg Deposition (%) 10 ● a-Se to t-Se conversion not complete -140● Repeat experiment with additional 0 -160cleaning measures installed behind -reactive surface & adatoms possible 5 1015202530 t-Se Distance (cm)Au clean gas-filled separator

References [1] Chiera, N. M. (2016). Towards the Selenides of the Superheavy Elements and : Inauguraldissertation Der Philosophisch-naturwissenschaftlichen Fakultät Der Universität Bern (Doctoral dissertation, DCB). [2] Gaggeler, H. W. (2009). Mendeleev’s principle against Einstein’s relativity : news from the chemistry of superheavy elements. Russian Chemical Reviews, 78(12), 1139–1144. https://doi.org/10.1070/RC2009v078n12ABEH004051 [3] Zvara, I. (1985). Simulation of Thermochromatographic Processes by the Monte Carlo Method. Radiochimica Acta, 38, 95–101.