[en] The production cross sections for the actinide products from ¹³⁶Xe bombardments of ²⁴⁹Cf at energies 1.02, 1.09, and 1.16 times the Coulomb barrier were determined. Fractions of the individual actinide elements were chemically separated from recoil catcher foils. The production cross sections of the actinide products were determined by measuring the radiations emitted from the nuclides within the chemical fractions. The chemical separation techniques used in this work are described in detail, and a description of the data analysis procedure is included. The actinide production cross section distributions from these ¹³⁶Xe + ²⁴⁹Cf bombardments are compared with the production cross section distributions from other heavy ion bombardments of actinide targets, with emphasis on the comparison with the ¹³⁶Xe + ²⁴⁹Cm reaction. In addition a technique for modeling the final actinide cross section distributions has been developed and is presented

[en] The production cross sections for the actinide products from ¹³⁶Xe bombardments of ²⁴⁹Cf at energies 1.02, 1.09, and 1.16 times the Coulomb barrier were determined. Fractions of the individual actinide elements were chemically separated from recoil catcher foils. The production cross sections of the actinide products were determined by measuring the radiations emitted from the nuclides within the chemical fractions. The chemical separation techniques used in this work are described in detail, and a description of the data analysis procedure is included. The actinide production cross section distributions from these ¹³⁶Xe + ²⁴⁹Cf bombardments are compared with the production cross section distributions from other heavy ion bombardments of actinide targets, with emphasis on the comparison with the ¹³⁶Xe + ²⁴⁸Cm reaction. A technique for modeling the final actinide cross section distributions has been developed and is presented. In this model, the initial (before deexcitation) cross section distribution with respect to the separation energy of a dinuclear complex and with respect to the Z of the target-like fragment is given by an empirical procedure. It is then assumed that the N/Z equilibration in the dinuclear complex occurs by the transfer of neutrons between the two participants in the dinuclear complex. The neutrons and the excitation energy are statistically distributed between the two fragments using a simple Fermi gas level density formalism. The resulting target-like fragment initial cross section distribution with respect to Z, N, and excitation energy is then allowed to deexcite by emission of neutrons in competition with fission. The result is a final cross section distribution with respect to Z and N for the actinide products. 68 refs., 33 figs., 6 tabs

[en] Techniques used in recent studies of the chemical and nuclear properties of elements 103-105 will be discussed. Similar techniques have also recently been used in the study of electron capture-delayed fission of neutron-deficient actinides. These techniques allow the study of isotopes with sub-minute half-lives and production rates of less than one atom per minute. A review of recent results will also be presented

[en] A set of eight stand-alone sample chambers with a common interface were constructed at LBNL for improved detection of alpha and fission decay chains over currently used designs. The stainless steel chambers (see Figure 1 for a schematic and Figure 2 for a photograph of a completed chamber) were constructed to allow for low background detection of a daughter event by removal of the sample following the detection of a parent event. This mother-daughter mode of operation has been utilized successfully with our Merry-go-Round (MG) detection system[Gregorich 1994]

[en] A multicomponent decay curve analysis technique has been developed and incorporated into the decay curve fitting computer code, MLDS (maximum likelihood decay by the simplex method). The fitting criteria are based on the maximum likelihood technique for decay curves made up of time binned events. The probabilities used in the likelihood functions are based on the Poisson distribution, so decay curves constructed from a small number of events are treated correctly. A simple utility is included which allows the use of discrete event times, rather than time-binned data, to make maximum use of the decay information. The search for the maximum in the multidimensional likelihood surface for multi-component fits is performed by the simplex method, which makes the success of the iterative fits extremely insensitive to the initial values of the fit parameters and eliminates the problems of divergence. The simplex method also avoids the problem of programming the partial derivatives of the decay curves with respect to all the variable parameters, which makes the implementation of new types of decay curves straightforward. Any of the decay curve parameters can be fixed or allowed to vary. Asymmetric error limits for each of the free parameters, which do not consider the covariance of the other free parameters, are determined. A procedure is presented for determining the error limits which contain the associated covariances. The curve fitting procedure in MLDS can easily be adapted for fits to other curves with any functional form. (orig.)

[en] A novel, fast and simple separation procedure is presented for separation of plutonium from lighter actinides and fission products. Classical methods, such as TTA-extraction and anion exchange resin techniques, were examined but failed to provide sufficient separation from lighter actinides. A successful procedure based on solid phase extraction chromatography was developed. Plutonium was effectively separated from interfering activities within 8 minutes using TEVA-resino, a quaternary amine-based liquid anion exchanger sorbed on an inert support. Recoveries of about 70 percent were achieved for plutonium with decontamination factors of 105 to 106 from neptunium, uranium and thorium

[en] Techniques used in recent studies of the chemical and nuclear properties of elements 103-105 will be discussed. Similar techniques have also recently been used in the study of electron capture-delayed fission of neutron-deficient actinides. These techniques allow the study of isotopes with sub-minute half-lives and production rates of less than one atom per minute. A review of recent results will also be presented

[en] The isotope ²⁶⁰Lr produced in reactions of ¹⁸O with ²⁴⁹Bk was used to perform chemical experiments on lawrencium to learn more about its chemical properties. These experiments involved extractions with thenoyl trifluoroacetate (TTA), ammonium alpha-hydroxyisobutyrate (HIB) elution from a cation exchange resin column, and reverse-phase chromatography using hydrogen di(2-ethylhexyl)orthophosphoric acid (HDEHP) to investigate the chemical properties of Lr. The results from the HIB elutions also give information about the ionic radius of Lr(III) which was found to elute very close to Er. An attempt to reduce Lr(III) was also made

[en] Ion exchange techniques have been an indispensable tool in the study of the transactinide elements. These techniques have been used to determine the most basic chemical properties of the transactinide elements, such as their positions within the periodic table. More recently, ion exchange has been used to study the chemical properties of the transactinide elements and their lighter homologs. This chemical knowledge has, in turn, been used to study the nuclear properties of isotopes of the transactinide elements

[en] 65-s ²⁶¹Rf and 34-s ²⁶²Ha have been produced at the Lawrence Berkeley Laboratory 88-Inch Cyclotron by the ²⁴⁸Cm(¹⁸O,5n) and ²⁴⁹Bk(¹⁸O,5n) reactions, respectively. These isotopes of element 104 and 105 are produced at a one atom per minute rate, and rapid chemical separations are performed on a one-minute time scale. They are identified by detecting the α- and SF radiations from their decay. First aqueous phase chemical separations of Rf and Ha determined their primary oxidation states in aqueous solution, placing them in the periodic table at the bottom of groups 4 and 5, respectively, and confirming Seaborg's actinide concept. More recently, experiments measuring the chemical properties in more detail have uncovered some interesting and unexpected trends in periodic table properties