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

Description: Several reactions producing odd-Z transactinide compound nuclei were studiedwith the 88-Inch Cyclotron and the Berkeley Gas-Filled Separator at the LawrenceBerkeley 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 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.
Date: May 14, 2008
Creator: Nelson, Sarah L & Nelson, Sarah L
Partner: UNT Libraries Government Documents Department


Description: Although the deleterious effects of exposure to ionizing radiation were first recognized and described over fifty years ago, the adequate treatment of these effects still remains a therapeutic challenge. At the present time, when increasing numbers of our population are being exposed to radiation because of the great increase in availability and use of radioactive isotopes and because of the potential exposure of much greater numbers of people to radiation following a possible atomic bomb burst or from disseminated radioactivity, the need for development of adequate therapy is becoming an increasingly pressing medical problem. In a consideration of possible approaches to therapy, one must distinguish between radiation front sources external to the body and radiation which results from radioactive materials which by some means or other have gained access into the body. Internally deposited radiation emitters can be particularly insidious since so many of them become fixed in the skeleton and are eliminated at very slow rates. While it is possible to remove external sources of damaging radiation once the hazard is recognized, the internal radiation emitters often are not readily displaced and the body remains exposed to prolonged continued radiation. Where long-lived elements, such as plutonium with a biological half-life of the order of 100 years or radium with one of 45 years, are involved, the body can be subject to continuous radiation for the remainder of its lifetime. Moreover, because the radiation persists for such long periods of time, only minute amounts of certain radioelements, i.e., plutonium and radium, need have entered initially to produce considerable injury. The effects of this type of chronic exposure to radiation are well documented in the case reports on radium poisoning in workers in the luminous dial industry. The damage is manifest in various forms, i.e., severe anemia, osteitis, and osteogenic sarcoma. ...
Date: June 14, 1951
Creator: Foreman, Harry & Hamilton, Joseph G.
Partner: UNT Libraries Government Documents Department

On Double-Beta Decay Half-Life Time Systematics

Description: Recommended 2{beta}(2{nu}) half-life values and their systematics were analyzed in the framework of a simple empirical approach. T{sub 1/2}{sup 2{nu}} {approx} 1/E{sup 8} trend has been observed for {sup 128,130}Te recommended values. This trend was used to predict T{sub 1/2}{sup 2{nu}} for all isotopes of interest. Current results were compared with other theoretical and experimental works.
Date: April 14, 2010
Creator: Pritychenko, B.
Partner: UNT Libraries Government Documents Department


Description: The H-F conductance and susceptance were determined for coil-type vessels over a range of frequencies from 2 to 30 mc. The ultraviolet absorption spectra of organic compounds in the vapor phase were determined, and a maximum was assigned to each compound. The dielectric constant values for five alpha substituted ketones at 25 deg C are reponted. A series of acids in dimethylformamide was titrated with the alkali methoxides by the high-frequency and conductance methods. The titration curves by these two methods were very similar in shape and also very similar to the curves for the corresponding type of acid in aqueous solution (W.L.H.)
Date: September 14, 1959
Partner: UNT Libraries Government Documents Department

Activation Measurements for Thermal Neutrons, U.S. Measurements of 36Cl in Mineral Samples from Hiroshima and Nagasaki; and Measurement of 63 Ni in Copper Samples From Hiroshima by Accelerator Mass Spectrometry

Description: The present paper presents the {sup 36}Cl measurement effort in the US. A large number of {sup 36}Cl measurements have been made in both granite and concrete samples obtained from various locations and distances in Hiroshima and Nagasaki. These measurements employed accelerator mass spectrometry (AMS) to quantify the number of atoms of {sup 36}Cl per atom of total Cl in the sample. Results from these measurements are presented here and discussed in the context of the DS02 dosimetry reevaluation effort for Hiroshima and Nagasaki atomic-bomb survivors. The production of {sup 36}Cl by bomb neutrons in mineral samples from Hiroshima and Nagasaki was primarily via the reaction {sup 35}Cl(n,{gamma}){sup 36}Cl. This reaction has a substantial thermal neutron cross-section (43.6 b at 0.025 eV) and the product has a long half-life (301,000 y). hence, it is well suited for neutron-activation detection in Hiroshima and Nagasaki using AMS more than 50 years after the bombings. A less important reaction for bomb neutrons, {sup 39}K(n,{alpha}){sup 36}Cl, typically produces less than 10% of the {sup 36}Cl in mineral samples such as granite and concrete, which contain {approx} 2% potassium. In 1988, only a year after the publication of the DS86 final report (Roesch 1987), it was demonstrated experimentally that {sup 36}Cl measured using AMS should be able to detect the thermal neutron fluences at the large distances most relevant to the A-bomb survivor dosimetry. Subsequent measurements in mineral samples from both Hiroshima and Nagasaki validated the experimental findings. The potential utility of {sup 36}Cl as a thermal neutron detector in Hiroshima was first presented by Haberstock et al. who employed the Munich AMS facility to measure {sup 36}Cl/Cl ratios in a gravestone from near the hypocenter. That work subsequently resulted in an expanded {sup 36}Cl effort in Germany that paralleled the US work. More recently, ...
Date: January 14, 2005
Creator: Straume, Tore; Marchetti, Alfredo A.; Egbert, Stephen D.; Roberts, James A.; Men, Ping; Fujita, Shoichiro et al.
Partner: UNT Libraries Government Documents Department