Odd-Z Transactinide Compound Nucleus Reactions Including the Discovery of 260Bh

Thesis/Dissertation · Tue Jan 01 00:00:00 EST 2008

DOI:https://doi.org/10.2172/929699· OSTI ID:929699

Nelson, Sarah L. ^[1]

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1. Univ. of California, Berkeley, CA (United States)

Several reactions producing odd-Z transactinide compound nuclei were studiedwith the 88-Inch Cyclotron and the Berkeley Gas-Filled Separator at the Lawrence Berkeley National Laboratory. The goal was to produce the same compound nucleus ator near the same excitation energy with similar values of angular momentum via differentnuclear reactions. In doing so, it can be determined if there is a preference in entrancechannel, because under these experimental conditions the survival portion of Swiatecki, Siwek-Wilcznska, and Wilczynski's"Fusion By Diffusion" model is nearly identical forthe two reactions. Additionally, because the same compound nucleus is produced, theexit channel is the same. Four compound nuclei were examined in this study: ²⁵⁸Db, ²⁶²Bh, ²⁶⁶Mt, and ²⁷²Rg. These nuclei were produced by using very similar heavy-ion induced-fusion reactions which differ only by one proton in the projectile or target nucleus (e.g.: ⁵⁰Ti + ²⁰⁹Bi vs. ⁵¹V + ²⁰⁸Pb). Peak 1n exit channel cross sections were determined for each reaction in each pair, and three of the four pairs' cross sections were identical within statistical uncertainties. This indicates there is not an obvious preference of entrancechannel in these paired reactions. Charge equilibration immediately prior to fusionleading to a decreased fusion barrier is the likely cause of this phenomenon. In addition to this systematic study, the lightest isotope of element 107, bohrium, was discovered in the ²⁰⁹Bi(⁵²Cr,n) reaction. ²⁶⁰Bh was found to decay by emission of a 10.16 MeV alpha particle with a half-life of 35$$+19\atop{-9}$$ ms. The cross section is 59 pb at an excitation energy of 15.0 MeV. The effect of the N = 152 shell is also seen in this isotope's alpha particle energy, the first evidence of such an effect in Bh. All reactions studied are also compared to model predictions by Swiatecki, Siwek-Wilcznska, and Wilczynski 's" Fusion By Diffusion " theory.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP)
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 929699
• Report Number(s): LBNL-312E; TRN: US0803515
• Resource Relation: Related Information: Designation of Academic Dissertation: Doctoral Thesis; Academic Degree: Doctor of Philosophy in Chemistry; Name of Academic Institution: University of California, Berkeley; Location of Academic Institution: Berkeley, California
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
ALPHA PARTICLES
ANGULAR MOMENTUM
BOHRIUM
COMPOUND NUCLEI
CROSS SECTIONS
CYCLOTRONS
DECAY
DIFFUSION
EXCITATION
HALF-LIFE
NUCLEAR REACTIONS
NUCLEI
PROJECTILES
PROTONS
TARGETS
TRANSACTINIDE COMPOUNDS
transactinide
compound nucleus reaction
88-Inch Cyclotron
Berkeley Gas Filled Separator
BGS