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Dmitriy A. Mayorov • Texas A&M University • Cyclotron Institute

Production of elements near the N = 126 shell in hot fusion-evaporation reactions with 48 Ca, 50 Ti, and 54 Cr projectiles on lanthanide targets. Dmitriy A. Mayorov • Texas A&M University • Cyclotron Institute . Motivation for Present Work.

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Dmitriy A. Mayorov • Texas A&M University • Cyclotron Institute

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  1. Production of elements near the N = 126 shell in hot fusion-evaporation reactions with 48Ca, 50Ti, and 54Cr projectiles on lanthanide targets Dmitriy A. Mayorov • Texas A&M University • Cyclotron Institute

  2. Motivation for Present Work 1. reduction in PCN for reactions with 50Ti and beyond on actinide targets 2. how will the predicted closed shell character of Z = 120, N = 184 and the correspond shell correction energy affect production cross section for elements 119 and 120? PCN Ratio (48Ca →50Ti) ≈ 10 (48Ca →54Cr) ≈ 49 2 A. K. Nasirovet al., Phys. Rev. C 84, 044612 (2011). Picture courtesy of Superheavy Elements Group, GSI

  3. Previous Research: Reduced Survival Probabilities of Weakly Deformed Nuclei • 4He + 226Ra → 230Th * • 18O + 208Pb → 224Th * • 48Ca + 172,173,176Yb → 212,213, 216Th * • 16O + 206Pb → 222Th * • 40Ar + 176,178,180Hf → 216, 218, 220Th * Calculation excluding collective enhancements Calculation excluding shell effects Calculation including collective enhancements and shell effects 3 P. Armbruster, Reports on Progress in Physics 62, 465 (1999). C. C. Sahmet al., Nucl. Phys. A 441, 316 (1985).

  4. Schematic Depiction of Collective Enhancements CN CN β2 > 0.15 β2 > 0.15 β2 ≈ 0.15+ β2 < 0.15 Fission Saddle Point Neutron Emission Fission Saddle Point Neutron Emission • fade-out with increasing E*modeled by: 4 R. Junghanset al., Nucl. Phys. A 629, 635 (1998) V. I. Zagrebaevet al., Phys. Rev. C 65, 014607 (2001)

  5. N = 126 Reaction Systems of Interest 5 A. Sobiczewski and K. Pomorski, Prog. Part. Nucl. Phys. 58, 292 (2007).

  6. MARS – Momentum Achromat Recoil Spectrometer K500 Cyclotron 6 R. E. Tribble et al., Nucl. Instrum. Meth. A 285, 441 (1989). C. M. Folden III et al., Nucl. Instrum. Meth. A 678, 1 (2012).

  7. Production of 4n EVR in 48Ca + 162Dy relative to 54Cr + 162Dy • upper limits are at an 84% confidence interval • pxn evaporation channels are more prominent for neutron-deficient nuclei • theoretical calculations based on the statistical codes of the NRV group D. Vermeulenet al., Z. Phys. A.-Hadrons Nuclei 318, 157 (1984).

  8. Production of 4n EVR in 48Ca + 162Dy relative to 54Cr + 162Dy ≈ 4 ≈ 270 without collective enhancements ≈7100 with collective enhancements • Separation between the dashed curves if primary accounted for by the differences in Bf-Bn(≈ 6 MeV) • Bn and Bfdetermine the magnitudes of GnandGf, which determines psp(E*) • Fade-out is an exponential function of E*, which is affected by Bn along the de-excitation cascade 8 W. J. Swiateckiet al., Phys. Rev. C 78, 054604 (2008).

  9. Production of 4n EVR in 50Ti + 159Tb Preliminary excitation function for 50Ti + 159Tb CN: 210Rn (N = 124) PCN ≈ 0.5 CN: 209Fr (N = 122) CN: 216Th (N = 126) PCN ≈ 0.25 PCN ≈ 0.1* • Collective enhancements become more pronounced • PCN rough estimate based on: Phenomenological Formula: 48Ca + 162Dy/50Ti +159Tb 1.7 48Ca + 162Dy/54Cr +162Dy 3.4 9 D. Vermeulenet al., Z. Phys. A.-Hadrons Nuclei 318, 157 (1984). C. C. Sahmet al., Nucl. Phys. A 441, 316 (1985). K. Siwek-Wilczynskaet al., Int. J. Mod. Phys. E 17, 12 (2008).

  10. Rotating Wheel Target MARS – Momentum Achromat Recoil Spectrometer Ongoing Improvements to Experimental Set-Up MCP K150 Hi-Temp Oven 10 T. Loewet al., IEEE Particle Accelerator Conference, 2963 (2007).

  11. Concluding Remarks • Previous authors recognized the impact that collective enhancements may have on SHE synthesis. • In the present experimental effort: • ~ a systematic investigation of projectile on reaction cross section is of interest • ~ the behavior of collective enhancements in these systems is of importance • Further data needed to deduce systematic trends/behavior • Use of more detailed theoretical analysis • At present, the current theoretical predictions of the production cross section of tens of fb for 120 • seems most reliable.

  12. Acknowledgements • Special Thanks To: • Group • Cyclotron Institute Staff • NRV Group of JINR (especially A. V. Karpov) • Funding: • DoE under award numbersDE-FG02-93ER40773 and MUSC09-100 • Welch Foundation under grant number A-1710 12

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