Searching the Stabilizing Effects of Neutron Shell Closure via Fusion Evaporation Residue Studies

Authors: B. R. S. Babu, E. Prasad, P. V. Laveen, A. M. Vinodkumar

Abstract:

Searching the “Island of stability” is a topic of extreme interest in theoretical as well as experimental modern physics today. This “island of stability” is spanned by superheavy elements (SHE's) that are produced in the laboratory. SHE's are believed to exist primarily due to the “magic” stabilizing effects of nuclear shell structure. SHE synthesis is extremely difficult due to their very low production cross section, often of the order of pico barns or less. Stabilizing effects of shell closures at proton number Z=82 and neutron number N=126 are predicted theoretically. Though stabilizing effects of Z=82 have been experimentally verified, no concluding observations have been made with N=126, so far. We measured and analyzed the total evaporation residue (ER) cross sections for a number of systems with neutron number around 126 to explore possible shell closure effects in ER cross sections, in this work.

Keywords: Superheavy element, fusion evaporation, evaporation reside, compound nucleus.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1338724

References:

[1] Yu Ts Oganessian and V K Utyonkov “Super Heavy Element Search” Rep. Prog. Phys. 78, 036301 (2015).
[2] Rohit Sandal, B. R. Behera, et al., “Probing nuclear dissipation via evaporation residue excitation functions for the O16,18+Pt198 reactions” Phys. Rev. C 91, 044621 (2015).
[3] W. J. Swiatecki, The dynamics of nuclear coalescence or Respiration Physica scripta” 24, 1B (1981) 113
[4] J. Tōke, R. Bock, et al., Quasi-fission — The mass-drift mode in heavyion reactions” , Nuclear Phys. A440 , 327 (1985)
[5] D. Vermeulen, H.-G. Clerc, C.-C. Sahm… “Cross sections for evaporation residue production near theN=126 shell closure”, Z. Phys. A 318, 157 (1984).
[6] N Madhavan, S Nath, et al. “Hybrid recoil mass analyzer at IUAC–First results using gas-filled mode and future plans” Pramana 75, 317 (2010).
[7] E. Prasad, et al., “Evaporation residue excitation function measurement for the 16O+194Pt reaction” Phys. Rev. C 84, 064606 (2011).
[8] Jhilam Sadhukan, Ph D thesis, Homi Bhabha National, Institute (Unpublished)
[9] N. Bohr and J. A. Wheeler, “The mechanism of Nuclear Fission” Phys. Rev 56, 426 (1936).
[10] E. Prasad et al., “Fission fragment angular distribution measurements for 16O +194Pt reaction at energies near the Coulomb barrier” Nucl. Phys. A 882, 62 (2012).
[11] P. Frobrich and I. I. Gontchar, “Langevin description of fusion, deepinelastic collisions and heavy-ion-induced fission” Phys. Rep. 292, 131(1998)
[12] A. V. Ignatyuk et al., Sov. J. Nucl. Phys. 21, 255 (1975).
[13] H. A. Kramers “Brownian motion in a field of force and the diffusion model of chemical reactions” 7, 284 (1940).
[14] R. J. Charity, J.R. Leigh et al., “Heavy-ion induced fusion-fission systematics and the effect of the compound-nucleus spin distribution on fission-barrier determination” Nucl. Phys. A 457, 441 (1986).
[15] R. Rafeie et al., “Strong evidence for quasifission in asymmetric reactions forming 222Po” Phys. Rev. C77, 024606 (2008)
[16] R. N. Sagaidak and A. N. Andreyev “Fission barriers for Po nuclei produced in complete fusion reactions with heavy ions” Phys. Rev. C 79, 054613 (2009).