6 Matching Results

Search Results

Advanced search parameters have been applied.

Cold Fusion Production and Decay of Neutron-Deficient Isotopes of Dubnium and Development of Extraction Systems for Group V Elements

Description: Excitation functions for the 1n and 2n exit channels of the 208Pb(51V,xn)259-xDb reaction were measured. A maximum cross section of the 1n exit channel of 2070+1100/-760 pb was measured at an excitation energy of 16.0 +- 1.8 MeV. For the 2n exit channel, a maximum cross section of 1660+450/-370 pb was measured at 22.0 +- 1.8 MeV excitation energy. The 1n excitation function for the 209Bi(50Ti,n)258Db reaction was remeasured, resulting in a cross section of 5480+1730/1370 pb at an excitation energy of 16.0 +- 1.6 MeV. Differences in cross section maxima are discussed in terms of the fusion probability below the barrier. The extraction of niobium (Nb) and tantalum (Ta) from hydrochloric acid and mixed hydrochloric acid/lithium chloride media by bis(2-ethylhexyl) hydrogen phosphate (HDEHP) and bis(2-ethylhexyl) hydrogen phosphite (BEHP) was studied. The goal of the experiments was to find a system that demonstrates selectivity among the members of group five of the Periodic Table and is also suitable for the study of dubnium (Db, Z = 105). Experiments with niobium and tantalum were performed with carrier (10-6 M), carrier free (10-10 M) and trace (10-16 M) concentrations of metal using hydrochloric acid solution with concentrations ranging from 1 - 11 M. The extraction of niobium and tantalum from mixed hydrochloric acid/lithium chloride media by HDEHP and BEHP as a function of hydrogen ion (H+) concentration was also investigated. The data obtained are used as the basis to discuss the speciation of niobium and tantalum under the conditions studied and to evaluate possible extraction mechanisms. The 74Se(18O,p3n)88gNb excitation function was measured to determine the best energy for producing the 88Nb used in chemistry experiments. A maximum cross section of 495 +- 5 mb was observed at an 18O energy of 74.0 MeV. The half life of 88gNb was measured and determined ...
Date: July 31, 2008
Creator: Gates, Jacklyn M.
Partner: UNT Libraries Government Documents Department

Heavy-Ion Irradiation of Thulium(III) Oxide Targets Prepared by Polymer-Assisted Deposition

Description: Thulium(III) oxide (Tm{sub 2}O{sub 3}) targets prepared by the polymer-assisted deposition (PAD) method were irradiated by heavy-ion beams to test the method's feasibility for nuclear science applications. Targets were prepared on silicon nitride backings (thickness of 1000 nm, 344 {micro}g/cm{sup 2}) and were irradiated with an {sup 40}Ar beam at laboratory frame energy of {approx}210 MeV (50 particle nA). The root mean squared (RMS) roughness prior to irradiation is 1.1 nm for a {approx}250 nm ({approx}220 {micro}g/cm{sup 2}) Tm{sub 2}O{sub 3} target, and an RMS roughness of 2.0 nm after irradiation was measured by atomic force microscopy (AFM). Scanning electron microscopy of the irradiated target reveals no significant differences in surface homogeneity when compared to imaging prior to irradiation. Target flaking was not observed from monitoring Rutherford scattered particles as a function of time.
Date: September 15, 2008
Creator: Garcia, Mitch A.; Ali, Mazhar N.; Chang, Noel N.; Parsons-Moss, Tashi; Ashby, Paul D.; Gates, Jacklyn M. et al.
Partner: UNT Libraries Government Documents Department

Lightest Isotope of Bh Produced Via the 209Bi(52Cr,n)260BhReaction

Description: The lightest isotope of Bh known was produced in the new {sup 209}Bi({sup 52}Cr,n){sup 260}Bh reaction at the Lawrence Berkeley National Laboratory's 88-Inch Cyclotron. Positive identification was made by observation of eight correlated alpha particle decay chains in the focal plane detector of the Berkeley Gas-Filled Separator. {sup 260}Bh decays with a 35{sub -9}{sup +19} ms half-life by alpha particle emission mainly by a group at 10.16 MeV. The measured cross section of 59{sub -20}{sup +29} pb is approximately a factor of four larger than compared to recent model predictions. The influences of the N = 152 and Z = 108 shells on alpha decay properties are discussed.
Date: May 7, 2007
Creator: Nelson, Sarah L.; Gregorich, Kenneth E.; Dragojevic, Irena; Garcia, Mitch A.; Gates, Jacklyn M.; Sudowe, Ralf et al.
Partner: UNT Libraries Government Documents Department

Comparison of reactions for the production of 258,257Db: 208Pb(51V,xn) and 209Bi(50Ti,xn)

Description: Excitation functions for the 1n and 2n exit channels of the 208Pb(51V,xn)259-xDb reaction were measured. A maximum cross section of the 1n exit channel of 2070+1100/-760 pb was measured at an excitation energy of 16.0 +- 1.8 MeV. For the 2n exit channel, a maximum cross section of 1660+450/-370 pb was measured at 22.0 +- 1.8 MeV excitation energy. The 1n excitation function for the 209Bi(50Ti,n)258Db reaction was remeasured, resulting in a cross section of 5480+1750/-1370 pb at an excitation energy of 16.0 +- 1.6 MeV, in agreement with previous values [F. P. Hebberger, et al., Eur. Phys. J. A 12, 57 (2001)]. Differences in cross section maxima are discussed in terms of the fusion probability below the barrier.
Date: September 29, 2008
Creator: Gates, Jacklyn M.; Nelson, Sarah L.; Gregorich, Kenneth E.; Dragojevic, Irena; Dullmann, Christoph E.; Ellison, Paul A. et al.
Partner: UNT Libraries Government Documents Department

Synthesis of rutherfordium isotopes in the 238U(26Mg, xn)264-xRf reaction and study of their decay properties

Description: Isotopes of rutherfordium (258-261Rf) were produced in irradiations of 238U targets with 26Mg beams. Excitation functions were measured for the 4n, 5n and 6n exit channels. Production of 261Rf in the 3n exit channel with a cross section of 28+92-26 pb was observed. Alpha decay of 258Rf was observed for the first time with an alpha-particle energy of 9.05+-0.03 MeV and an alpha/total decay branching ratio of 0.31+-0.11. In 259Rf, the electron capture/total decay branching ratio was measured to be 0.15+-0.04. The measured half-lives for 258Rf, 259Rf and 260Rf were 14.7+1.2-1.0 ms, 2.5+0.4-0.3 s and 22.2+3.0-2.4 ms, respectively, in agreement with literature data. The systematics of the alpha decay Q values and of the partial spontaneous fission half-lives were evaluated for even-even nuclides in the region of the N = 152, Z = 100 deformed shell. The influence of the N = 152 shell on the alpha decay Q values for rutherfordium was observed to be similar to that of the lighter elements (96<_ Z<_ 102). However, the N = 152 shell does not stabilize the rutherfordium isotopes against spontaneous fission, as it does in the lighter elements (96<_ Z<_102).
Date: January 15, 2008
Creator: Gates, Jacklyn M; Gates, J.M.; Garcia, M.A.; Gregorich, K.E.; Dullmann, Ch.E.; Dragojevic, I. et al.
Partner: UNT Libraries Government Documents Department

New Superheavy Element Isotopes: 242Pu(48Ca,5n)285114

Description: The new, neutron-deficient, superheavy element isotope {sup 285}114 was produced in {sup 48}Ca irradiations of {sup 242}Pu targets at a center-of-target beam energy of 256 MeV (E* = 50 MeV). The {alpha} decay of {sup 285}114 was followed by the sequential {alpha} decay of four daughter nuclides, {sup 281}Cn, {sup 277}Ds, {sup 273}Hs, and {sup 269}Sg. {sup 265}Rf was observed to decay by spontaneous fission. The measured {alpha}-decay Q values were compared with those from a macroscopic-microscopic nuclear mass model to give insight into superheavy element shell effects. The {sup 242}Pu({sup 48}Ca,5n){sup 285}114 cross section was 0.6{sub -0.5}{sup +0.9} pb.
Date: October 22, 2010
Creator: Ellison, Paul A; Gregorich, Kenneth E.; Berryman, Jill S.; Bleuel, Darren L.; Clark, Roderick M.; Dragojevic, Irena et al.
Partner: UNT Libraries Government Documents Department