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The Eight New Synthetic Elements

Description: In an early continuation of the investigation of the radioactive isotopes of element number 43 (technetium) Segre and Seaborg produced by the deuteron and neutron bombardment of molybdenum the isotope Tc{sup 99}, which they observed to decay by means of an isomeric transition with a half-life of 6.6 hours to a lower isomeric state with a half-life greater than 40 years. The upper isomeric state of this isotope was observed by Segre and C. S. Wu to be produced in the fission of uranium and more recently R. P. Schumann and also D. C. Lincoln and W. H Sullivan working on the Plutonium Project of the Manhattan District have independently observed the beta-particles of half-life about 10 years due to the lower isomeric state. Later work by E. E. Motta and G. E. Boyd sets a more accurate value of 9.4 x 10{sup 5} years for this half-life. Since this isotope is formed in rather large amounts, namely, a fission yield of 6.2%, in the slow neutron induced fission of uranium it is now possible to isolate technetium in weighable amounts and in rather substantial quantities. For example, a uranium pile operating at a power level of 10{sup 5} kw would produce about four grams of technetium, as the isotope T{sup 99}, per day. With such a long half-life the radioactivity associated with convenient amounts (some mg.) would be so small in intensity as to not create a problem provided reasonable care in handling were exercised.
Date: November 1, 1947
Creator: Seaborg, Glenn T.
Partner: UNT Libraries Government Documents Department

The occurrence of plutonium in nature

Description: Plutonium has been chemically separated from seven different ores and the ratios of plutonium to uranium determined. This ratio was found to be fairly constant in pitchblende and monazite ores, in which the uranium content varied from 50% t o 0.24%, and substantially less in carnotite and fergusonite.
Date: November 29, 1950
Creator: Levine, Charles A. & Seaborg, Glenn T.
Partner: UNT Libraries Government Documents Department

CHARTING THE NEW ELEMENTS

Description: This article reviews the history of the discovery of new elements and the current state of knowledge of the transuranic elements.
Date: October 1, 1980
Creator: Seaborg, Glenn T.
Partner: UNT Libraries Government Documents Department

Evidence for Subshell at Z = 96

Description: The evidence is decisive that major nuclear shells are completed at 82 protons and 126 neutrons (both represented by the nuclide Pb{sup 208}) and these, along with major shells at 82 neutrons and certain lower nucleon numbers (N or Z = 20, 28, 50), are well explained by the strong spin orbit coupling model of Mayer and Haxel, Jensen, and Suess. This model suggests the filling of quantum states at certain intermediate points, and there is an accumulating amount of evidence that such 'sub shells' are also discernible, for example, at Z = 58 and Z = 64. The evidence from alpha radioactivity, both (1) the effect of the nuclear radius shrinkage on the relationship between energy and half-life and (2) the discontinuities in the plots of energy vs. mass number at constant Z, gives a striking indication of the closing of major shells at Z = 82 and N = 126. Application of these sensitive criteria as tests for the much smaller 'subshell' effects in the regions Z > 82 and N > 126 leads to some evidence for such a subshell at Z = 96 (curium).
Date: September 3, 1953
Creator: Seaborg, Glenn T.
Partner: UNT Libraries Government Documents Department

Nuclear Thermodynamics of the Heaviest Elements

Description: The phenomenon of alpha particle emission, a general observable property for the nuclides above lead, makes it possible to relate these nuclides energetically. The radioactive decay energy along a radioactive series can be summed so that the total decay energy for each nuclide in the series is known with respect to its position above teh bottom of the series, that is, with respect to its terminal lead (or bismuth) isotope. This can be done for each of the four mass types and, as shown, one can obtain this information for all the collateral members as well as the members in the main line of decay. Thus it is possible, using the relation between mass and energy and the known mass of the alpha particle, to convert this radioactive decay energy ine ach case to a relative mass value based on the mass of one of the four end products, Pb{sup 208}, Pb{sup 207}, Pb{sup 206}, or Bi{sup 209}. If the absolute mass of each of these is known, it is then possible to calculate the absolute mass for all the heavy nuclides above lead for which decay energy data are known or can be estimated. The absolute mass of only one of this group of four need actually be known since the neutron binding energies related them can be measured. it is also possible to measure the absolute masses of other nuclei in each of the four series, for example, such nuclides as U{sup 238}, Th{sup 232}, U{sup 235}, or Np{sup 237} which are available in sufficient quantity for mass spectrographic measurements, and the aboslute masses of the other members of each of the series may then be calculated from these through proper use of the decay data. if the absolute masses of more than one member of the same ...
Date: March 1, 1952
Creator: Seaborg, Glenn T.
Partner: UNT Libraries Government Documents Department

Some Comments on the Mechanism of Fission

Description: A correlation of spontaneous fission rates with Z and A is made to show that these rates depend on the nuclear type. Some suggestions as to the mechanisms are given and it is also shown how these relate to the mechanism of slow neutron and photo fission.
Date: July 25, 1951
Creator: Seaborg, Glenn T.
Partner: UNT Libraries Government Documents Department

Activation Energy for Fission

Description: The experimentally determined exponential dependence of spontaneous fission rate on Z{sup 2}/A has been used to derive an expression for the dependence of the fission activation energy on Z{sup 2}/A. This expression has been used to calculate the activation energy for slow neutron induced fission and photofission. The correlation with the experimental data on these types of fission seems to be quite good.
Date: August 29, 1952
Creator: Seaborg, Glenn T.
Partner: UNT Libraries Government Documents Department

The Transcalifornium Elements

Description: During the past sixty years, four elements beyond californium on the atomic number scale have been synthesized by the transmutation of lighter elements. The first preparation of einsteinium and fermium occurred in a thermonuclear explosion. Mendelevium and element 102, however, were prepared by a more conventional method, that of charged particle bombardment of elements of high atomic number.
Date: December 8, 1958
Creator: Seaborg, Glenn T.
Partner: UNT Libraries Government Documents Department

Recent Developments in the Field of the TransplutoniumElements

Description: The author tells about some of the most interesting aspects of recent research on the synthetic transplutonium elements. The amount of recent information on these elements is obviously too much to cover completely in the time that has been placed at my disposal. Therefore, in planning my talk, I have attempted to choose those topics which have the broadest implications for the whole transuranium field of research. Although much important and interesting research is, of course, being done in many laboratories, I have chosen examples mainly from the work in our own laboratory, the Radiation Laboratory at the University of California in Berkeley. I shall cover this information about the known transplutonium elements, listed in Slide No. 1, by discussing them in order of increasing atomic number, and I shall conclude with some thoughts concerning the prospects for elements with higher atomic numbers than any that have been produced and identified up to the present time. For purposes of orientation, Slide No. 2 shows the position in the periodic table of the presently known and the future transuranium elements. The transplutonium elements through element 103, together with the five preceding elements, are members of the 'heavy rare earth', or actinide transition series, which is analogous to the lighter rare easth, or lanthanide, transition series. The undiscovered 'trans-103' elements will fit into the periodic table as shown. I shall, of course, refer in my talk to the important unifying principle embodied in the periodic table.
Date: September 10, 1958
Creator: Seaborg, Glenn T.
Partner: UNT Libraries Government Documents Department

Recent Work with the Transuranium Elements

Description: In this discussion of the heaviest known elements, the author describes some recent research which appears to offer the most promise for future investigations. As a general background, the author reviews briefly the history and properties of the transuranium elements.
Date: November 1, 1958
Creator: Seaborg, Glenn T.
Partner: UNT Libraries Government Documents Department

Early History of Heavy Isotope Research at Berkeley

Description: I have had the idea for some time that it would be interesting and worthwhile to put together an account of the early work on heavy isotopes at Berkeley. Of a special interest is the discovery of plutonium (atomic number 94) and the isotope U{sup 233}, and the demonstration of their fission with slow neutrons. This work served as a prelude to the subsequent Plutonium Project (Metallurgical Project) centered at the University of Chicago, in connection with which I have also had the idea of putting together a history of the work of my chemistry group. I have decided that it would be an interesting challenge to write this account on a day-to-day basis in a style that would be consistent with the entries having been written at the end of each day. The aim would be to make this history as accurate as possible by going back to the original records and using them with meticulous care.
Date: June 1, 1976
Creator: Seaborg, Glenn T.
Partner: UNT Libraries Government Documents Department

Peaceful uses of nuclear energy

Description: It is now a quarter of a century since nuclear energy was introduced to the public. Its introduction was made in the most dramatic, but unfortunately in the most destructive way - through the use of a nuclear weapon. Since that introduction enormous strides have been made in developing the peaceful applications of this great and versatile force. Because these strides have always been overshadowed by the focusing of public attention on the military side of the atom, the public has never fully understood or appreciated the gains and status of the peaceful atom. This booklet is an attempt to correct, in some measure, this imbalance in public information and attitude. It is a compilation of remarks, and excerpts of remarks, that I have made in recent years in an effort to bring to the public the story of the remarkable benefits the peaceful atom has to offer man. This is a story that grows with the development and progress of the peaceful atom. It must be told so that we can learn to use the power of nuclear energy wisely and through this use help to build a world in which the military applications of the atom will never again be a threat to mankind.
Date: January 1, 1970
Creator: Seaborg, Glenn T.
Partner: UNT Libraries Government Documents Department

Nuclear Thermodynamics of the Heaviest Elements. II

Description: The masses of the isotopes of the heaviest elements have been calculated from known decay data in the region, extended by means of decay energies calculated from closed decay-energy cycles and estimated from the systematics of alpha and beta decay energies. The absolute values of the masses are based on the mass-spectrometrically determined mass of Pb{sup 208} and a few measured neutron binding energies. The half-life systematics of alpha decay and spontaneous fission are also presented, and some predictions of the properties of as yet undiscovered nuclides are made.
Date: October 1, 1957
Creator: Foreman Jr., Bruce M. & Seaborg, Glenn T.
Partner: UNT Libraries Government Documents Department

Nuclear Thermodynamics of the Heaviest Elements. II

Description: The masses of the isotopes of the heaviest elements have been calculated from known decay data in the region, extended by means of decay energies calculated from closed decay-energy cycles and estimated from the systematics of alpha and beta decay energies. The absolute values of the masses are based on the mass-spectrometrically determined mass of Pb{sup 208} and a few measured neutron binding energies. The half-life systematics of alpha decay and spontaneous fission are also presented, and some predictions of the properties of as yet undiscovered nuclides are made.
Date: January 1, 1958
Creator: Foreman Jr., Bruce M. & Seaborg, Glenn T.
Partner: UNT Libraries Government Documents Department

Extension of Alpha- and Beta-Decay Systematics of ProtactiniumIsotopes

Description: As part of the program for obtaining data to extend the scope of the systematics of alpha-radioactivity and to obtain more data pertaining to the energy surface in the heavy region of elements, they have made some pertinent new measurements on protactinium isotopes. The heaviest isotope of protactinium hitherto reported is that of mass 234 and hence it would be of interest to know the beta-emission properties of heavier isotopes in order to tie them in with the known radioactive data in this general region. Since low-energy deuteron bombardment of U{sup 238} might be expected to lead to Pa{sup 235} and Pa{sup 236} by (d,{alpha}n) and (d,{alpha}) reactions and proton bombardment to Pa{sup 235} by the (p,{alpha}) reaction, these irradiations were made in the 60-inch cyclotron at energies of 19 and 9.5 Mev, respectively. The protactinium was chemically separated following the bombardment of natural uranium by a procedure which involved a number of manganese dioxide cycles coupled with extractions of protactinium from aqueous into organic solvents. The manganese dioxide cycles consisted of precipitating this compound from the solution of uranium in nitric acid, followed by centrifugation, dissolution of the solid with hydroxylamine solution, dilution, and reprecipitation. The dissolved precipitate from the last cycle was acidified, salted with ammonium nitrate, and the protactinium extracted with diisopropyl ketone, several washings with salted solutions being made to insure good separation from fission products. The protactinium was then washed back into a low acidity aqueous solution and after acidification was extracted into a benzene solution of thenoyltrifluoroacetone which forms a complex ion with the protactinium. This solution was then evaporated to dryness on a platinum counting plate leaving a weightless deposit of protactinium.
Date: January 30, 1950
Creator: Meinke, W. Wayne & Seaborg, Glenn T.
Partner: UNT Libraries Government Documents Department

FISSION OF GOLD BY CARBON IONS

Description: Angular distribution and kinetic-energy spectra of fragments, and cross sections for fission of gold with 68- to 124-Mev C{sup 12} ions have been obtained by observation of the fragments in two types of detectors, gas scintillation chambers and silicon p-n junctions. From the parameters used to fit the angular distributions to the theoretical curves of Halpern and Strutinski, we have obtained the average excitation energy of the fissioning nucleus at the time of fission. This quantity is approximately 25 Mev, which is nearly independent of bombarding energy, suggesting that fission is preceded by the emission of several particles from the compound nucleus. The fission cross section increases from a value of 100 mb at 68 Mev to 1.28 b. at 124 Mev. Over this range of bombarding energies, the total fragment kinetic-energy release rises from 142 {+-} 6 to 146 {+-} 6 Mev. At all bombarding energies, the variation of laboratory-system kinetic energy of the fragments with laboratory-system angle indicates full momentum transfer by the bombarding particle to the fissioning system.
Date: June 8, 1960
Creator: Gordon, Glen E.; Larsh, Almon E.; Sikkeland, Torbjorn & Seaborg,Glenn T.
Partner: UNT Libraries Government Documents Department

The Ion-Exchange Separation of Zirconium and Hafnium

Description: In the course of a rather cursory examination of the elution of tetra-positive ions from the cation exchange resin Dowex 50 with hydrochloric acid solutions, the authors have discovered a very effective method of separating zirconium from hafnimu. In view of the great labor involved in preparing even reasonably pure hafnium compounds by existing methods, they feel that this procedure will prove very valuable to those interested in obtaining hafnium compounds free of zirconium. Although the conditions which give satisfactory separation were first worked out using microgram amounts of material and the radioactive tracer technique, the run described here, involving milligrams of material, illustrates the applicability of the method to the production of significant amounts of pure hafnium and zirconium.
Date: October 11, 1948
Creator: Street, Kenneth, Jr. & Seaborg, Glenn T.
Partner: UNT Libraries Government Documents Department

ANGULAR DISTRIBUTION OF FRAGMENTS FROM FISSION INDUCED BY HEAVYIONS IN GOLD AND BISMUTH

Description: We present the results of measurements of the angular distribution of fission fragments produced by irradiation of Au{sup 197} and Bi{sup 209} with various heavy ions. The projectiles, B{sup 11}, C{sup 12}, N{sup 14}, and O{sup 16}, had energies from a few MeV above the Coulomb barrier to 10.4 MeV per nucleon. The gross features of these results can be explained by use of a model and parameters that have been used by others to account for angular distributions of fission fragments from helium-ion bombardments. In detail, however, these results appear to indicate that the models used to predict the average value of the angular momentum of the compound nucleus give values too low near the Coulomb barrier. Furthermore, at high bombarding energies it is necessary to consider the fact that appreciable direct interaction is taking place.
Date: May 21, 1962
Creator: Viola, Victor E.; Thomas, T. Darrah & Seaborg, Glenn T.
Partner: UNT Libraries Government Documents Department

CHEMICAL PROPERTIES OF BERKELIUM

Description: The recent production by Thompson, Ghiorso, and Seaborg of a radioactive isotope of berkelium (atomic number 97) makes it possible to investigate the chemical properties of this transuranium element by means of the tracer technique. This isotope has been prepared through the bombardment of Am{sup 241} with about 35 Mev helium ions in the 60-inch cyclotron of the Crocker Laboratory and is believed to have the mass number 243, or possibly 244. This Bk{sup 243} has a half-life of 4.6 hours and decays by electron capture with about 0.1% branching decay by alpha-particle emission. In the present tracer chemical experiments, the radiations accompanying the electron capture process were used as a means of detection and were counted in two ways. Where the sample deposits on the platinum plates were essentially weightless, as was the case following the evaporation and ignition of the elutriant solutions in the column adsorption experiments, a high efficiency was obtained by using a windowloess proportional counter to count the Auger electrons. The thicker samples from the precipitation experiments in which carrier materials were used were counted close to the thin window (3 mg/cm{sup 2} mica) of a bell type Geiger counter filled with 10 cm. xenon to enhance the efficiency for counting the x-rays. An aluminum absorber of thickness about 20 mg/cm{sup 2} was used between the sample and counter window to reduce errors due to variable absorption of soft components caused by small differences in sample thickness.
Date: February 24, 1950
Creator: Thompson, Stanley G. & Seaborg, Glenn T.
Partner: UNT Libraries Government Documents Department

Activation Energy for Fission

Description: Abstract: The experimentally determined exponential dependence of spontaneous fission rate on Z^2/A has been used to derive an expression for the dependence of the fission activation energy on Z^2/A. This expression has been used to calculate the activation energy for slow neutron induced fission and photofission. The correlation with the experimental data on these types of fission seems to be quite good.
Date: August 29, 1952
Creator: Seaborg, Glenn T.
Partner: UNT Libraries Government Documents Department

PROCEEDINGS OF THE SYMPOSIUM COMMEMORATING THE 25th ANNIVERSARY OF ELEMENTS 97 and 98 HELD ON JAN. 20, 1975

Description: This volume includes the talks given on January 20, 1975, at a symposium in Berkeley on the occasion of the celebration of the 25th anniversary of the discovery of berkelium and californium. Talks were given at this symposium by the four people involved in the discovery of these elements and by a number of people who have made significant contributions in the intervening years to the investigation of their nuclear and chemical properties. The papers are being published here, without editing, in the form in which they were submitted by the authors in the months following the anniversary symposium, and they reflect rather faithfully the remarks made on that occasion.
Date: July 1, 1976
Creator: Seaborg, Glenn T.; Street Jr., Kenneth; Thompson, Stanley G. & Ghiorso, Albert
Partner: UNT Libraries Government Documents Department