Adsorption of the Lighter Homologs of Element 104 and Element 105 on DGA Resin from Various Mineral Acids
The goal of studying transactinide elements is to further understand the fundamental principles that govern the periodic table. The current periodic table arrangement allows for the prediction of the chemical behavior of elements. The correct position of a transactinide element can be assessed by investigating its chemical behavior and comparing it to that of the homologs and pseudo-homologs of a transactinide element. Homologs of a transactinide element are the elements in the same group of the periodic table as the transactinide. A pseudo-homolog of a transactinide element is an element with a similar main oxidation state and similar ionic radius to the transactinide element. For example, the homologs of rutherfordium, Rf, are titanium, zirconium and hafnium (Ti, Zr and Hf); the pseudo homologs of Rf are thorium, Th, and plutonium, Pu. Understanding the chemical behavior of a transactinide element compared to its homologs and pseudo-homologs also allows for the assessment of the role of relativistic effects. Relativistic effects occur when the velocity of the s orbital electrons closest to the nucleus approaches the speed of light. These electrons approach the speed of light because they have no orbital momentum. This causes two effects, first there is in a decrease in Bohr radius of the inner electronic orbitals because of this there is an increase in particle mass. A contraction of outer s and p orbitals is also seen. The contraction of these orbitals results in an energy destabilization of the outer most shell, in the case of transactinides this would be the 5f and 6d orbitals. The outer most d shell and all f shells can also experience a radial expansion due to these orbitals being screened from the effective nuclear charge. Another relativistic effect is the 'spin-orbit splitting' for p, d and f orbitals into j = 1 {+-} 1/2 states. Where j is the total angular momentum vector and 1 is angular quantum number. All of these effects have the same order of magnitude and increase roughly according to Z. This feature is what makes studying the heavy elements so interesting because the chemical properties of transactinide elements should strongly exhibit these effects. For this work the terms heavy element and transactinide elements will be used interchangeably and are defined as elements with an atomic number greater than 103, Z > 103. In order to study the transactinide elements they must be isolated once they have been produced and transported to a chemistry apparatus. The transactinide elements are produced either via 'hot' or 'cold' fusion reactions. 'Hot' fusion reactions result in excitation energies of the compound nucleus of 40-50 MeV and occur when an actinide target nuclei fuse with a projectile with A < 40, where A is the atomic mass number. 'Cold' fusion results in excitation energies of 10-15 MeV. Cold fusion conditions tend to occur when a target of a spherical nuclei (Pb or Bi) is bombarded with a heavy projectile (A > 40). Hot fusion generally leads to neutron rich isotopes and cold fusion tends to produce a compound nucleus that emits 1-2 neutrons upon de-excitation. If a sufficiently thin target is employed, then the products of the nuclear reaction will recoil out of the target and can either be transported to the chemistry setup, e.g. using a gas jet, or trapped by implementing them on a catcher. An example for a catcher setup using a copper block as a catcher is described here. The copper block is placed behind the target during the irradiation and all nuclei recoiling from the target position will implant themselves in the block. The copper block is subsequently dismounted and sputter cleaned. It is then shaved with a micro-lathe. The 7-10 {micro}m copper shavings are then subjected to chemical separation. The copper is dissolved in aqua regia. Lanthanum carrier is added to the aqua regia to precipitate tri-, tetra- and penta- valent cations when ammonium hydroxide is added. The precipitate is then washed and converted to the nitrate form. This solution is then added onto a cation exchange column, the eluent is deposited and dried on a polypropylene film and then counted on solid state detectors. There are several challenges when studying the chemical behavior of transactinide elements. The first challenge is the low production rate of transactinides. Transactinides are produced on an atom-at-a-time basis, meaning that only one atom is ever available for chemical study. Because of this the chemical system being used must be selective for only one chemical state. The second challenge in transactinide chemistry is the short half-lives of the elements. Half-lives of the transactinides range from nanoseconds to a few hours. This leads to the need for fast chemistry. Another challenge is the need for a high degree of separation from interfering radionuclides so that the event with the transactinide element can be detected.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 945879
- Report Number(s):
- LLNL-SR-409699; TRN: US0901254
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ACTINIDES
ADSORPTION
AMMONIUM HYDROXIDES
ANGULAR MOMENTUM
AQUA REGIA
ATOMIC NUMBER
CHEMICAL PROPERTIES
CHEMICAL STATE
CHEMISTRY
COLD FUSION
COPPER
DUBNIUM
EXCITATION
INORGANIC ACIDS
MASS NUMBER
NEUTRON-RICH ISOTOPES
NUCLEAR REACTIONS
NUCLEI
QUANTUM NUMBERS
RADIOISOTOPES
RESINS
TRANSACTINIDE ELEMENTS
VALENCE