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Experiments of the Effect of Atomic Electrons on the DecayConstant of Be7

Description: In an attempt to detect a possible influence of the atomic electrons on the radioactive decay constant of Be{sup 7} they have measured {lambda}{sub Be}-{lambda}{sub BeO} and found (-3.0 {+-} 1.8) 10{sup -4} {lambda}{sub Be}. They describe also a method to measure mean lives of radioactive substances in a time short compared with the mean life.
Date: July 1, 1948
Creator: Segre, Emilio & Wiegand, Clyde
Partner: UNT Libraries Government Documents Department

Electronic Structure of the Heaviest Elements

Description: All of the available evidence leads to the view that the 5f electron shell is being filled in the heaviest elements giving rise to a transition series which begins with actinium in the same sense that the rare earth or 'lanthanide' series begins with lanthanum. Such an 'actinide' series is suggested on the basis of evidence in the following lines: (1) chemical properties, (2) absorption spectra in aqueous solution and crystals, (3) crystallographic structure data, (4) magnetic susceptibility data and (5) spectroscopic data. The salient point is that the characteristic oxidation state (i.e., the oxidation state exhibited by the member containing seven 5f and presumably also by the member containing fourteen 5f electrons, curium and element 103) is the III state, and the group is placed in the periodic table on this basis. The data also make it possible to give a suggested table of electronic configurations of the ground state of the gaseous atom for each of the elements from actinium to curium inclusive.
Date: July 14, 1948
Creator: Seaborg, G.T.
Partner: UNT Libraries Government Documents Department

Some Excitation Functions of Bismuth

Description: Excitation functions have been measured, using a 38-Mev alpha-beam and a 19-Mev deuteron beam for the following reactions: Bi({alpha},2n)At{sup 211}, Bi({alpha},3n)At{sup 210}, Bi(d,p)Ra E, Bi(d,n)Po{sup 210}, and Bi(d,3n)Po{sup 209}. The results are summarized in Figs. 4 and 5 and Tables I and II. A new isotope of astatine, At{sup 210}, has been identified; this isotope has a half life of 8.3 hr., decaying by K-capture to Po{sup 210} with the emission of a 1.0-Mev gamma-ray and a few conversion electrons.
Date: October 10, 1948
Creator: Kelly, E.L. & Segre, E.
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

An Isotope Effect in a Simple Chemical Reaction

Description: It has been found that the carbon dioxide obtained from the decarboxylation of singly-carboxyl labeled malonic acid is impoverished in the C{sup 14} label and that the acetic acid formed is correspondingly enriched.
Date: July 13, 1948
Creator: Yankwich, Peter E. & Calvin, Melvin
Partner: UNT Libraries Government Documents Department

An Isotope Effect in Photosynthesis

Description: In the course of some kinetic studies on photosynthesis of barley seedlings, it has been found that plants utilize C{sup 12}O{sub 2} faster than C{sup 14}O{sub 2}. The plants were placed in a closed system containing an infra-red absorption-cell for the analysis of total CO{sub 2} and an ionization chamber for the determination of C{sup 14}O{sub 2} in the gas phase, both instruments recording continuously. Carbon dioxide, containing about 2% C{sup 14}O{sub 2}, was introduced in the dark and the specific activity at this point taken as unity. After a short dark period, the lights were turned on and photosynthesis was allowed to take place. A figure shows the result of a typical experiment. During the initial dark period the specific activity fell because of dilution by inactive respired CO{sub 2}. However, as photosynthesis proceeded, the specific activity of the residual CO{sub 2} rose until, when only 1/6 of it remained, the specific activity reached a peak some 20% higher than it had been at the start of photosynthesis. At this point the steady respiratory dilution became an appreciable fraction of the total remaining CO{sub 2}, and the specific activity dropped rapidly.
Date: November 23, 1948
Creator: Weigl, J.W. & Calvin, M.
Partner: UNT Libraries Government Documents Department

Paramagnetic Suseptibilities and Electronic Structure of AqueousCations of Elements 92 to 95

Description: Magnetic susceptibilities per gram atomic weight of elements 92 to 95 in most of their oxidation states were measured on 0.1 ml of solution which was 0.007 to 0.09 M in heavy element. The values obtained (all paramagnetic) in c.g.s. units x 10{sup 6} were: U(IV), 3690; Np(VI), 2060; Np(V), 4120; Np(IV), 4000; Pu(IV), 1610; Pu(III), 370; Am(III), 720. The results could be interpreted only on the basis of electronic configurations 5f{sup n}, even though susceptibilities were generally lower than the theoretical values and lower than experimental values for corresponding lanthanide cations. The lower values should be expected as a result of the Stark effect produced by fields of anions and of water dipoles. Failure of the Russell-Saunders approximation to the coupling between electrons may account for some of the error in the theoretical calculations. Wider multiplet splitting in the actinides accounts for the fact that the susceptibilities of Pu(III) and Am(III) are many-fold lower than those of Sm(III) and Eu (III) respectively.
Date: November 12, 1948
Creator: Howland, Jerome J. & Calvin, Melvin
Partner: UNT Libraries Government Documents Department

The Path of Carbon in Photosynthesis

Description: The dark fixation of carbon dioxide by green algae has been investigated and found to be closely related to photosynthesis fixation. By illumination in the absence of carbon dioxide followed by treatment with radioactive carbon dioxide in the dark, the amount fixed has been increased ten to twenty fold. This rate of maximum fixation approaches photosynthesis maximum rates. The majority of the radioactive products formed under these conditions have been identified and isolated and the distribution of labeled carbon determined. From these results a tentative scheme for the mechanism of photosynthesis is set forth.
Date: March 8, 1948
Creator: Calvin, M. & Benson, A.A.
Partner: UNT Libraries Government Documents Department

The Path of Carbon in Photosynthesis II. Amino Acids

Description: The radioactive amino acid's synthesized from C{sup 14}O{sub 2} by green algae both in the light and in the dark after CO{sub 2}-free preillumination have been separated and identified using paper chromatography and radioautography. The radioactive amino acids identified were aspartic acid, alanine and smaller amounts of 3- and 4-carbon amino acids. This finding as well as the total absence of radioactive glutamic acid substantiates the mechanism for reduction of CO{sub 2} previously postulated by members of this laboratory.
Date: May 25, 1948
Creator: Stepka, W.; Benson, A.A. & Calvin, M.
Partner: UNT Libraries Government Documents Department

Path of Carbon in Photosynthesis III

Description: Although the overall reaction of photosynthesis can be specified with some degree of certainty (CO{sub 2} + H{sub 2}O + light {yields} sugars + possibly other reduced substances), the intermediates through which the carbon passes during the course of this reduction have, until now, been largely a matter of conjecture. The availability of isotopic carbon, that is, a method of labeling the carbon dioxide, provides the possibility of some very direct experiments designed to recognize these intermediates and, perhaps, help to understand the complex sequence and interplay of reactions which must constitute the photochemical process itself. The general design of such experiments is an obvious one, namely the exposure of the green plant to radioactive carbon dioxide and light under a variety of conditions and for continually decreasing lengths of time, followed by the identification of the compounds into which the radioactive carbon is incorporated under each condition and time period. From such data it is clear that in principle, at least, it should be possible to establish the sequence of compounds in time through which the carbon passes on its path from carbon dioxide to the final products. In the course of shortening the photosynthetic times, one times, one ultimately arrives at the condition of exposing the plants to the radioactive carbon dioxide with a zero illumination time, that is, in the dark. Actually, in the work the systematic order of events was reversed, and they have begun by studying first the dark fixation and then the shorter photosynthetic times. The results of the beginnings of this sort of a systematic investigation are given in Table I which includes three sets of experiments, namely a dark fixation experiment and two photosynthetic experiments, one of 30 seconds duration and the other of 60 seconds duration.
Date: June 1, 1948
Creator: Benson, A.A. & Calvin, M.
Partner: UNT Libraries Government Documents Department

The Path of Carbon in Photosynthesis IV. The Identity and Sequencefo the Intermediates in Sucrose Synthesis

Description: The synthesis of sucrose from C{sup 14}0{sub 22} by green algae has been investigated and the intermediates separated by the method of paper chromatography. It is shown that sucrose is the first free sugar appearing during photosynthesis. It is apparently formed by condensation of the glucose-I-phosphate and a fructose phosphate. A series of radioautographs of paper chromatograms of extracts from plants which have photosynthesized for different periods of time has been prepared. The results indicate that 2-phosphoglyceric acid is the first product synthesized from C0{sub 2} during photosynthesis.
Date: December 14, 1948
Creator: Calvin, M. & Benson, A.
Partner: UNT Libraries Government Documents Department

N-17, A Delayed Neutron Emitter

Description: The decay scheme of a 4.2 second neutron emitter has been investigated in detail. Chemical and physical evidence shows that it is N{sup 17}, which emits beta rays to a broad excited state of O{sup 17}, which then breaks up into a neutron plus O{sup 16}. The energy spectrum of the neutrons is determined by measuring the energies of the O{sup 16} recoils in a proportional counter. The neutrons have a most probable energy of 0.9 Mev, a 'half width' of less than .5 Mev, and an upper limit of about 2 Mev. {beta}-recoil coincidences are observed, as predicted by the Bohr-Wheeler theory, and the {beta}-ray energy is measured by absorption. The beta rays in coincidence with neutrons have an upper limit of 3.7 {+-} 0.2 Mev. Beta-rays directly to the ground stat of O{sup 17} are not observed because of high background effects, but should have an energy of 8.7 Mev. Some evidence is presented to show that energy is conserved in the {beta}-n transition through the broad excited state in O{sup 17}.
Date: November 5, 1948
Creator: Alvarez, L. W.
Partner: UNT Libraries Government Documents Department

Artificial Collateral Chains to the Thorium and ActiniumFamilies

Description: The authors have produced and identified two new series of alpha-particle emitting radioactive elements; one is a 'collateral' branch of the actinium (4n + 3) radioactive family and the other is collateral to the thorium (4n) family. The series are of considerable interest in that they are the first whose early members lie on the neutron deficient side of beta stability. They have been produced in high yield of irradiation of thorium with deuterons of energy about {sup 80}Mev in the Berkeley 184-inch cyclotron. So far as the present observations are concerned both of these series begin with isotopes of protactinium (atomic number 91), although progenitors with higher atomic numbers are to be expected and will possibly be produced and identified. These protactinium isotopes are Pa{sup 227} and Pa{sup 228} formed by d,7n and d,6n reactions respectively.
Date: July 1, 1948
Creator: Ghiorso, A.; Meinke, W.W. & Seaborg, G.T.
Partner: UNT Libraries Government Documents Department

Monthly Progress Report No. 61 for May, 1948

Description: This is the University of California, Radiation Laboratory monthly progress report for May 1948. It discusses the following: (1) 184-inch Cyclotron Program; (2) 60-inch Cyclotron Program; (3) Synchrotron Program; (4) Linear Accelerator Program; (5) Experimental Physics; (6) Theoretical Physics, (7) Isotope Separation Program; (8) Chemistry Departments; (9) Medical Physics; and (10) Health Physics and Chemistry.
Date: May 31, 1948
Creator: Authors, Various
Partner: UNT Libraries Government Documents Department

The Isolation and Properties of Curium

Description: The isolation of curium, element number 96, in relatively pure form has been accomplished. A method, involving a solvent extraction process, is given for the purification of americium from lanthanum and other ions. The discovery of a higher oxidation state of americium led to a method of separating americium from curium. Separation of the two elements was also accomplished by use of ion exchange resins. The details of the isolation of curium are given; the results of the spectrographic analysis, specific activity measurement, and calorimetric determination of half life showed the curium to be relatively pure. The absorption of light of various wave-lengths by an aqueous solution of Cm(III) is described, and some physical effects of the radiation from the curium are noted.
Date: August 1, 1948
Creator: Werner, Louis B.
Partner: UNT Libraries Government Documents Department

Isolation and Propterties of Curium

Description: The isolation of curium, element number 96, in relatively pure form has been accomplished. A method, involving a solvent extraction process, is given for the purification of americium from lanthanum and other ions. The discovery of a higher oxidation state of americium led to a method of separating americium from curium. Separation of the two elements was also accomplished by use of ion exchange resins. The details of the isolation of curium are given; the results of the spectrographic analysis, specific activity measurement, and calorimetric determination of half life showed the curium to be relatively pure. The absorption of light of various wave-lengths by an aqueous solution of Cm(III) is described, and some physical effects of the radiation from the curium are noted.
Date: July 28, 1948
Creator: Werner, L.B. & Perlman, I.
Partner: UNT Libraries Government Documents Department

Progress Report No. 63 June 15-July 15, 1948

Description: This is the University of California, Radiation Laboratory progress report for June 15-July 15, 1948. It discusses the following: (1) 184-inch Cyclotron Program; (2) 60-inch Cyclotron Program; (3) Synchrotron Program; (4) Linear Accelerator Program; (5) Experimental Physics; (6) Theoretical Physics, (7) Isotope Separation Program; (8) Chemistry Departments; (9) Medical Physics; and (10) Health Physics and Chemistry.
Date: July 30, 1948
Creator: Authors, Various
Partner: UNT Libraries Government Documents Department

Progress Report No. 62 June 1-15, 1948

Description: This paper reports on the following programs: (1) 184-inch Cyclotron Program; (2) 60-inch Cyclotron Program; (3) Synchrotron Program; (4) Linear Accelerator Program; (5) Experimental Physics; (6) Theoretical Physics; (7) Isotope Separation Program; (8) Chemistry; and (9) Medical Physics.
Date: June 30, 1948
Partner: UNT Libraries Government Documents Department

Progress Report No. 65 Aug. 15-Sept. 15, 1948

Description: This is a progress report on the following: (1) 184-inch Cyclotron Program; (2) 60-inch Cyclotron Operation; (3) Synchrotron Program; (4) Linear Accelerator Operation; (5) Experimental Physics; (6) Theoretical Physics; (7) Isotope Separation Program; (8) Chemistry; (9) Medical Physics; and (10) Health Chemistry and Physics.
Date: September 15, 1948
Partner: UNT Libraries Government Documents Department

Monthly Progress Report No. 58 for February 1948

Description: This is a monthly progress report on the following programs: (1) 184-inch Cyclotron; (2) 60-inch Cyclotron; (3) Synchrotron; (4) Linear Accelerator; (5) Experimental Physics; (6) Theoretical Physics; (7) Isotope Research; (8) Chemistry; (9) Medical Physics; and (10) Health Physics and Chemistry.
Date: February 1, 1948
Partner: UNT Libraries Government Documents Department

Monthly Progress Report No. 59 for March 1948

Description: This monthly progress report covers the following programs: (1) 184-inch Cyclotron; (2) 60-inch Cyclotron; (3) Synchrotron; (4) Linear Accelerator; (5) Experimental Physics; (6) Theoretical Physics; (7) Chemistry; (8) Medical Physics; and (9) Health Physics and Chemistry.
Date: March 1, 1948
Partner: UNT Libraries Government Documents Department

Monthly Progress Report No. 60 for April 1948

Description: This report gives a short summary of each of the following programs: (1) 184-inch Cyclotron Program; (2) 60-inch Cyclotron Program; (3) Synchrotron Program; (4) Linear Accelerator Program; (5) Experimental Physics; (6) Theoretical Physics; (7) Chemistry; (8) Medical Physics; and (9) Health Physics and Chemistry.
Date: May 1, 1948
Partner: UNT Libraries Government Documents Department

Neutron Deficient Isotopes of Tellurium and Antimony

Description: While investigating the relative yields for the many reactions resulting from the irradiation of antimony with 200-Mev deuterons in the Berkeley 184-inch cyclotron several previously unreported isotopes of tellurium and antimony were encountered. The tellurium fraction when followed on a thin mica window counter could be resolved into half-life periods of 2.5 hrs, 6.0 days and a small amount of a long-lived component. The 2.5 hour period has not been further characterized with respect to mass number or mode of decay other than to note that the radiation is predominantly electrons. The 6.0-day period is accompanied by positrons which were shown to be due to a 3.5 minute antimony daughter which is undoubtedly the same activity assigned to Sb{sup 118} by Risser, Lark-Horowitz and Smith. The positron energy was found to be 3.1 {+-} 0.2 Mev by absorption in berylllum and from the end point of the energy distribution curve taken with a low-resolution beta-ray spectrometer. Gamma activity is also present with this period. The 6.0-day tellurium showed a high abundance of x-rays, little or no conversion electrons and some gamma-ray activity which could be due to the 3.5 minute antimony daughter. The tellurium fraction contained another component of 4.5-day half-life which could not be observed in the decay curve because of its low abundance but which was detected by means of its 39-hour antimony daughter. The 39-hour antimony showed x-rays of tin (critical absorption with cadmiium, silver and palladium), no detectable hard radiation or electrons and is apparently identical with an activity recently assigned to Sb{sup 119} by Coleman and Pool.
Date: January 1, 1948
Creator: Lindner, M. & Perlman, I.
Partner: UNT Libraries Government Documents Department

The Estimation of Heats of Formation

Description: The procedure for estimation of heats of formation of compounds is illustrated by discussion of compounds of several of the elements of the actinide series. The procedure is particularly suited for lanthanide and actinide elements because of the similarity of the ionic radii and types of bonding.
Date: February 2, 1948
Creator: Brewer, Leo
Partner: UNT Libraries Government Documents Department