Slide 1

Production of elements near the N = 126 shell in hot fusion-evaporation reactions with 48Ca, 50Ti, and 54Cr projectiles on lanthanide targetsDmitriy A. Mayorov Texas A&M University Cyclotron Institute 221.reduction in PCN for reactions with 50Ti and beyond on actinide targetsMotivation for Present Work

A. K. Nasirov et al., Phys. Rev. C 84, 044612 (2011).Picture courtesy of Superheavy Elements Group, GSI2.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

33

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 *P. Armbruster, Reports on Progress in Physics 62, 465 (1999).C. C. Sahm et al., Nucl. Phys. A 441, 316 (1985).Calculation excluding collective enhancementsCalculation excluding shell effectsCalculation including collective enhancements and shell effects

44Schematic Depiction of Collective Enhancements

R. Junghans et al., Nucl. Phys. A 629, 635 (1998)V. I. Zagrebaev et al., Phys. Rev. C 65, 014607 (2001)CN2 < 0.152 > 0.15Fission Saddle PointNeutron EmissionCN2 0.15+2 > 0.15Fission Saddle PointNeutron Emission

fade-out with increasing E*modeled by:

55

N = 126

Reaction Systems of InterestA. Sobiczewski and K. Pomorski, Prog. Part. Nucl. Phys. 58, 292 (2007).

6

K500 CyclotronMARS Momentum Achromat Recoil Spectrometer6

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 groupD. Vermeulen et al., Z. Phys. A.-Hadrons Nuclei 318, 157 (1984).788Production of 4n EVR in 48Ca + 162Dy relative to 54Cr + 162Dy

7100without collective enhancementswith collective enhancements

Separation between the dashed curves if primary accounted for by the differences in Bf-Bn ( 6 MeV)

Bn and Bf determine the magnitudes of Gn and Gf, which determines psp (E*)

Fade-out is an exponential function of E*, which is affected by Bn along the de-excitation cascade

4 270W. J. Swiatecki et al., Phys. Rev. C 78, 054604 (2008).99Production of 4n EVR in 50Ti + 159Tb Collective enhancements become more pronounced

PCN rough estimate based on: Preliminary excitation function for 50Ti + 159TbCN: 210Rn (N = 124)CN: 209Fr (N = 122)CN: 216Th (N = 126)

D. Vermeulen et al., Z. Phys. A.-Hadrons Nuclei 318, 157 (1984).C. C. Sahm et al., Nucl. Phys. A 441, 316 (1985). K. Siwek-Wilczynska et al., Int. J. Mod. Phys. E 17, 12 (2008).PCN 0.5PCN 0.25PCN 0.1*

Phenomenological Formula:48Ca + 162Dy/50Ti +159Tb1.748Ca + 162Dy/54Cr +162Dy3.41010MARS Momentum Achromat Recoil Spectrometer Ongoing Improvements to Experimental Set-Up

MCPRotating Wheel Target K150Hi-TempOven

T. Loew et al., IEEE Particle Accelerator Conference, 2963 (2007).

11Concluding 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.

1212Acknowledgements Special Thanks To:

Group

Cyclotron Institute Staff

NRV Group of JINR (especially A. V. Karpov)

Funding:

DoE under award numbers DE-FG02-93ER40773 and MUSC09-100

Welch Foundation under grant number A-1710