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In this paper we discuss the process of fission of even fermium isotopes, on the basis of their rotational states. The nuclear intrinsic vorticity and its coupling to the global rotation of the nucleus are used to simulate the interaction between the rotational motion and the pairing field, and lead to pairing quenching in the case of higher angular momentum states. The rotation leads to a decreasing of the fission barrier heights. The ingredients of the model—ground state fission barriers, pairing correlation energies and the cranking moments of inertia—are obtained within the self-consistent Hartree–Fock–Bogoliubov framework using the Skyrme energy density functional. Fission barriers and half-lives are estimated for spins I up to I = 16.

The actinide elements are a group of chemically similar elements with atomic numbers 89 through 103, and include actinium, thorium, protactinium, uranium, neptunium, plutonium, americium, curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium, and lawrencium. Each of the elements has a number of isotopes, all radioactive. Thorium, uranium, and plutonium are well known for their role as the basic fuels (or sources of fuel) for the release of nuclear energy. The importance of the remainder of the actinide group lies at present in research. The actinides present a storage-life problem in nuclear waste disposal. Only the members of the actinide group through Pu have been found to occur in nature. Thorium and uranium occur widely in the earth's crust in combination with other elements, and, in the case of uranium, in significant concentrations in the oceans. With these exceptions, the actinide elements are synthetic in origin for practical purposes, ie, they are products of nuclear reactions. All the actinide elements are radioactive, and, except for thorium and uranium, special equipment and shielded facilities are usually necessary for their manipulation. Special techniques for experimentation with the actinide elements other than Th and U have been devised because of the potential health hazard to the experimenter and the small amounts available. The actinide elements exhibit uniformity in ionic types. Corresponding ionic types are similar in chemical behavior, although the relative stabilities differ from element to element. Of the actinide ions, the small, highly charged ions exhibit the greatest degree of hydrolysis and complex ion formation. The actinide metals, like the lanthanide metals, are highly electropositive. They can be prepared by the electrolysis of molten salts or by the reduction of a halide with an electropositive metal, such as calcium or barium. Thousands of compounds of the actinide elements have been prepared. The elements beyond the actinides in the periodic table can be termed the transactinides. These begin with the element having atomic number 104 and extend, in principle, indefinitely. Nine such elements, numbers 104–1112, are now known, and evidence for the observation of elements 114, 116, and 118 was published in 1999. These reports now await confirmation. Thse elements are synthesized by the bombardment of heavy nuclides with heavy ions. Modern high-speed computers have made possible the calculation of the electronic structure of the atoms, which gives some general guidance about chemical properties. Recently, the even more difficult theoretical problem of predicting the behavior of molecular species under actual experimental conditions has been addressed using relativistic quantum-chemical calculations combined with fundamental physicochemical considerations. Keywords: Actinides; Transactinides; Productions; Nuclear; Chemical Properties

Purpose: This synopsis attempts to shed light on the progresses made in the field of cancer therapy using α-particles. Hurdles and Progresses: The rationale of selection of radionuclides focusing on comparison of α- and β-emitters, the hurdles and their solutions, and recent developments are addressed. The efforts made in the field of α-radioimmunotherapy of hematologic malignancies are emphasized. A good deal of progress has been achieved in the past decade, and preclinical studies with a variety of radioimmunoconjugates with astatine and bismuth radioisotopes (At-211, Bi-212, and Bi-213) have generated encouraging results, providing an impetus for future clinical trials. Conclusion: The onset of early clinical trials with α-emitters will hopefully enable the cancer researchers to come up with extremely effective and highly specific “smart bombs” to target cancer cells.

For the 60 years that have passed after the discovery of the first artificial elements Np and Pu, the investigations of the properties of new elements have become one of the fundamental and quickly developing fields of nuclear physics and nuclear chemistry. The transition from the traditional method of producing transuranium elements, where continuous and pulsed neutron fluxes have been used, to nuclear reactions induced by heavy ions has made it possible to synthesize 12 new elements heavier than fermium (Z=100). The theoretical description of the masses and fission barriers of the new nuclei led in the mid-1960s to the prediction of “islands of stability” for the very heavy and superheavy nuclides in the vicinity of the closed proton and neutron shells. The experimental data that demonstrate the enhanced stability of nuclei, close to the deformed shells Z=108 and N=162, relative to different decay modes and also the reactions of their synthesis are discussed from the point of view of advancing into an u...

We calculate complete fission potential-energy surfaces versus five shape coordinates: elongation, neck diameter, light-fragment deformation, heavy-fragment deformation, and mass asymmetry for even nuclei in the range 82⩽Z⩽100. The potential energy is calculated in terms of the macroscopic-microscopic model with a folded-Yukawa single-particle potential and a Yukawa-plus-exponential macroscopic model in the three-quadratic-surface parameterization. The structure of the calculated energy landscapes exhibits multiple valleys leading to different scission configurations. The properties of these valleys and the saddle-points at the beginning of these valleys can be directly related to bimodal fission properties observed in the radium region, in the light-actinide region, and in the fermium region). The rms deviation between calculated and experimental fission-barrier heights is only 1.08 MeV for 31 nuclei from 70Se to 252Cf.

We demonstrate experimentally and theoretically that the sign of two-wave coupling gain in sillenite crystal at some polarization of light changes with the increase of the amplitude of square-wave field applying along the axis. It is shown that the nonunidirectional energy exchange is the reason of this effect in Bi12TiO20 single crystal. Also strong influence of this effect on the polarization properties of the two-wave coupling gain was it revealed at the experimental investigations of the efficiency of the two-wave interaction in Bi12SiO20 single crystal. At the theoretical analysis we used the model obtained on the basic of the mode approach. Made the numerical calculation of dependencies of the two-wave coupling gain has good agreement with the experimental data. This calculation has allowed estimating the material parameters of the investigated samples of the crystal.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

An intrinsically time-resolved version of frequency-modulation (FM) spectroscopy has been recently developed and applied to the study of gas-phase photodissociation dynamics. Transient FM spectroscopy allows low background detection of radical species with shot-noise limited sensitivities, time resolution sufficient for detection of collisionless photoproducts, and frequency resolution characteristic of single-mode cw lasers. Methods for the quantitative analysis of Doppler-broadened FM line shapes to give velocity and rotational polarization information have been established permitting the measurement of scalar and vector properties of molecular fragmentation in exquisite detail. Several recent examples of the application of transient FM spectroscopy will be presented and discussed, including correlated scalar distributions in the dissociation of ketene from CH{sub 2}(a{sup 1} A{sub 1}) Doppler profiles, and the full vector correlation analysis of CN (X {sup 2}{Sigma}{sup +}) fragments arising from ICN dissociation.

The Evaluated Photon Data Library, 1997 version (EPLD97), is designed for use in photon transport calculations at Lawrence Livermore National Laboratory. This library includes photon interaction data for all elements with atomic number between Z = 1 (hydrogne) and 100 (fermium), including: photoionization, photoexcitation, coherent and incoherent scattering, and pair and triplet porduction cross sections. For use in applications data is provided for all elements over the energy range 1 eV to 100 GeV. This report documents the sources and treatment of the data included inthis library. EPDL97 completely supersedes the earlier 1989 version of EPDL and it is highly recommended that useres only use the most recent version of this library.

The Radiochemical Engineering Development Center at Oak Ridge National Laboratory processes irradiated targets to recover the transplutonium actinides for research and industrial users. In a typical processing campaign, dekagram quantities of curium are recovered for recycle into targets for subsequent irradiation and processing; decigram quantities of californium are recovered for fabrication into neutron sources; and milligram quantities of einsteinium and berkelium as well as picogram quantities of fermium are recovered for distribution to the research community. The transcurium actinides are separated in a series of chromatographic elutions using a cation-exchange resin and ammonium α-hydroxyisobutyrate as the eluant. The fermium fraction from these final purification runs still contains significant amounts of rare earth fission products, such as yttrium, dysprosium, and holmium. In the most recent campaign, a process using a TEVA™ resin extraction chromatography column was developed and tested to determine its effectiveness in providing a fermium product free of rare earth fission products. Gamma spectroscopy indicated that dysprosium and holmium were reduced to levels less than minimum detectable limits and that only 0.07 pg of 91Y remained in the final fermium product, which contained 0.5 pg of 257Fm. An overall decontamination factor of ∼ 103 was achieved for fission product removal.

The Skyrme-Hartree–Fock–Bogoliubov calculations of the energies of first 2+ rotational states of deformed superheavy (SH) elements in the region of 108 ≤ Z ≤ 126 and 148 ≤ N ≤ 180 are reported. The results agree well in the case of fermium isotopes after a proper scaling of the moment of inertia. The scaling factor equals 1.3. The extension of the model to the region of SH elements gives a possibility of better estimation of the Q-values of α-decay, which is a dominant decay mode of SH elements.

Accumulation of radioactive nuclear wastes all over the world is among the most severe ecological problems that must be solved without delay. In this regard, of great interest is the neutron method of transmutation of nuclear wastes using neutron fluxes from reactors. The neutron method of fusion of new elements is based on the successive capture of neutrons by the initial cores. The cores that absorbed neutrons undergo β-decay. As a result, new cores with masses and charges exceeding the initial ones are created. Interest in the neutron method arose in 1966, when a group of American physicists from the Los-Alamos National Laboratory performed underground experiments on thermonuclear fusion of transuranium elements in Nevada [1]. U and Am targets were irradiated by neutron fluxes produced during explosions of thermonuclear charges. The heaviest transuranium element they obtained was Fm. They tried to detect Fm and Md elements among the irradiation products, but did not succeeded. This failure was explained in 1980, when American physicists from the Los-Alamos and Livermore National Laboratories succeeded in fusion of Fm in the reaction Fm(t, p) Fm. The Fm half-life for spontaneous fission was T = 1.5 s. This is almost 10 times less than Т = 131 year for Fm [2]. Analogous decrease in Т with increasing number of neutrons in a fissionable nucleus was revealed in fusion of Fm in the reaction Fm(d, p) Fm [3]. For Fm, Т = 380 ± 60 μs, which is almost 10 times less than Т = 160 min for Fm [4]. The authors of these experiments explained this sharp destabilization of heavy fermium isotopes undergoing spontaneous fission by the shell structure of fragments. The latter become more and more close to the doubly magic nucleus Sn with Z = 50 and N = 82 as the number of neutrons in the fissionable nucleus increases. It should be noted that fragments of the heavy Fm isotopes – magic and nearly margic Sn–Sn isotopes – are weakly active cores. After a series of β-decays with half-lives from 2.2 min to 77.4 h they are transformed into stable Te or Xe cores [5]. Thus, the magic character of fragments of heavy fermium isotopes was a reason for their rapid spontaneous decay. Therefore, new transuranium elements with Z > 100 were not fused by the neutron method. The mendelevium element with Z = 101 was first discovered in USA in 1955 in the course of the nuclear reaction Еs(α, n) Md. The next elements with Z > 101 were fused in nuclear reactions with accelerated heavy ions [6]. Unsuccessful attempts to fuse the far transuranium elements [1] were caused by the unique obstacle – the predisposition of heavy fermium isotopes to spontaneous fission. This property could be useful for transmutation of nuclear wastes. There are grounds to believe that cores of radioactive wastes, including actinides and fission fragments, will gradually approach the fermium precipice in the process of neutron absorption and will end their existence in the form of weakly active Sn isotopes. These isotopes must be removed from the mixture of cores. Otherwise, the Sn isotopes can also start to absorb neutrons, new radionuclides will be accumulated, and the process as a whole will be reminiscent of the Sisyphys work. This work can be useful for the experts evaluating perspectives for the neutron method of transmutation of radioactive wastes.

AS A CODISCOVERER OF ALL OF the elements from 96 to 106 and of the earliest work on element 110,1 can attest to the fact that all of that research was exciting: It was an exploration into the unknown that required the development of new techniques that eventually developed sensitivities for identifying one atom at a time. But the discovery of elements 99 and 100 was something quite different. It was completely unexpected, a most extraordinary event that mimicked the r-process by which the heaviest elements were put on our Earth in the first place. It occurred in 1952, when the first thermonuclear device in history was exploded in the South Pacific by Los Alamos Scientific Laboratory. This was a highly secret event, and initially, the UC Radiation Laboratory was not involved in any way In fact, our first news that something very unusual had happened came when Glenn T. Seaborg received from Washington, D.C., ...

Electrochemical reduction of heavy elements from aqueous solution to amalgams was studied by radiopolarography and radiocoulometry. Mechanism of actinide reduction on a mercury pool is discussed through simulation techniques. Special emphasis is placed on redox reactions and potentials, kinetics of the process and effect of acetate and citrate ions as complexing agents. Three groups of actinides have been found. The first group represents actinium and from uranium to berkelium. Reduction occurs in the experimental conditions via an irreversible 3–0 process. The second group consists of the elements from fermium to nobelium, which are reduced in non-complexing solutions, or with acetate ions, similarly as barium and radium, via a reversible 2–0 reaction. Finally, californium and einsteinium behave as intermediate elements. It is noticeable that such groups are also observed in the actinide series by studying the structure of the trivalent aqua ions. On the basis of the above mentioned investigations of actinides and lanthanides several examples of electrochemical application are presented. Californium has been separated from preceding transuranium and lanthanide elements (except europium) by electrochemical reduction to amalgams in acetic solution. Separation factors from 25–90 are achieved with appropriate cathodic potentials. Similarly, this element could be separated from several heavier actinides with citric media. The electrochemical preparation of mixed uranium-nickel and uranium-tin amalgams from aqueous acetate solutions is investigated. The dependence of redox potentials of mixed amalgams on different atomic ratio U∶Ni and U∶Sn in amalgams is measured. The large shift of redox potentials of mixed amalgams to the positive direction is detected when the atomic ratio U∶Ni or U∶Sn in amalgams reaches 1∶5. The thermal distillation of mercury from mixed amalgams with different U∶Ni and U∶Sn atomic ratios was carried out and the products were identified by chemical analysis and X-ray diffraction. The intermetallics UNi5 and USn3 were prepared from mixed amalgams with the atomic ratios U∶Ni=1∶5 and U∶Sn=1∶3. The uranium and neptunium amalgams are prepared by electrolysis of aqueous acetate solutions and are processes into metals or nitrides U2N3, NpN by thermal distillation of mercury in vacuum or in nitrogen atmosphere.