Eskola, K.

Eskola, P.

Ghiorso, A.

Harris, J.

Nurmia, M.

eScholarship - University of California

Lawrence Berkeley National LaboratoryRecent WorkTitlePOSITIVE IDENTIFICATION OF TWO ALPHA PARTICLE EMITTING ISOTOPES OF ELEMENT 104Permalinkhttps://escholarship.org/uc/item/3fm666nqAuthorsGhiorso, A.Nurmia, M.Harris, J.et al.Publication Date1969-04-30eScholarship.org Powered by the California Digital LibraryUniversity of California., • I . • Submitted to Physical Review Letters UCRL-18819 Preprint POSITIVE IDENTIFICATION OF TWO ALPHA PARTICLE EMITTING ISOTOPES OF ELEMENT 104 A. Ghiorso, M. Nurmia, J. Harris, K. Eskola, and P. Eskola April 30, 1969 , .. AEC Contract No. W - 7 405 -eng -48 ...... ..... ~ ------• I~·~ , " . c.~~. LAWRENCE RADIATION LABORATORY f\ ..... 0 00 UNIVERSITY of CALIFORNIA BERKELEY -( ~ DISCLAIMER This document was prepared as an account of work sponsored by the United States Government. While this document is believed to contain correct information, neither the United States Government nor any agency thereof, nor the Regents of the University of California, nor any of their employees, makes any warranty, express or implied, or assumes any legal responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by its trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or the Regents of the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof or the Regents of the University of California. . UCRL-18819 POSITIVE IDENTIFICATION OF TWO ALPHA fARTICLE EMITTING * ISOTOPES OF ELEMENT 104 . "r :I: A. Ghiorso, M. Nurmia, Jo Harris, K. Eskola, P. Eskola Lawrence Radiation Laboratory University of California Berkeley, California April 30, 1969 ABSTRACT We have studied isotopes of element 104 formed by bombard-. 249 12 13 ing Cf with C and C ions. 257104 and 259104 were positively identified by milking their daughters, 253No and 255Noo 257104 is a 4.5-sec alpha particle, activity with a complex spectrumj 259104 'is likewise an alpha emitter with a half-life of 3 sec. 258104 is ten-, tatively identified as an ll-msec spontaneous fission activity. 1 In a recent report we have described our unsuccessful attempts to confirm the attribution by Dubna experimenters of a 0.3-second spontaneous 2 fission emitter to an isotope of element 1040 In this letter we will des-cribe what we believe are defini ti ve experiments which characterize the isotopes 257104 and 259104 • In addition, tentative evidence for 258104 is included. 3 249 A 60 microgram target of mono-isotopic Cf was electrodeposited from an isopropyl alcohol solution in an area of 0021 cm2 on a substrate sand-wich consisting of 001 mg/cm2 Pd sputtered onto 2.2 mg/cm2 Be. This 290 microgram/cm2 target was bombarded mainly by l2C and 13C ions accelerated by the Berkeley RILAC to make isotopes of element 104 but an appreciable fraction f th'e" b b d t 't 11_ 14N 15N 160 i C o om ar ments were conduc ed Wl h~, , ,and, ons. urrents in the range of 4 to 5 microamperes dc (as completely stripped ions) were -2-UCRL-18819 typically used and the total number of microamperehours was several thousands. The apparatus used was similar to that described in our papers 4,5 concerning the properties of various isotopes of nobelium. The transmuted atoms recoiling from the target were swept by helium gas from the target region operating at a pressure of about 500 torr through a 0.4 mm diameter orifice into vacuum to be deposited onto the periphery of a 45 cm diameter wheeL The digitally-controlled wheel was periodically rotated to place these atoms into positions adjacent to four Si-Au surface barrier crystal detectors6 so that after suitable amplification and analysis a.lpha particle spectra could be obtained. The energy and half-life data were stored in a ~DP-9 computer. The bombarding energy was measured with a solid state detector looking at o particles scattered from the target at an angle of 20 and was adjusted by means of Be metal foil degraders to reduce the energy of the 10.4 MeV/nucleon partic"les from the HILAC. The beam current was monitored by a wa ter-cooled Faraday cup. Because of the very high beam densities that were used, it was also necessary to liquid-cool the windows, the degrader fOils, and the target. 12 249 The . C bombardments of the Cf target produced a new alpha particle activity with a complex energy spectrum (Fig. 1) and a half-life of 4.5 ±LO seconds 0 The spectra were submitted to a computer analysis 7 with the result that four prominent alpha particle groups with energies 8.70, 8.78, 8.95, and 9.00 MeV and relative intensities 0.15, 0.2; 0.3, 0.35, respectively, were assigned to the activity. For alpha energy calibration, the 6.043 MeV peak of 209,21°Rn and the 7.43 MeV peak of 250Fm were used and extrapolation was made by use of a pulse generator. The absolute accuracy of the energy value s is estimated to be 0.02 MeV. The amount of activity was substantial (~5 cOlmts per microamperehour) and it was possible to measure its excitation function with good accuracy (Fig. 2). The function, with a maximum cross section of approximately 10-32 cm2, corresponds to that expected for the 12C,4n • , -3- UCRL-18819 reaction to produce 257104 and is consistent with the caiculations8 of Sikkeland and Lebeck. To make certain of the mass and atomic number of this activity, a series of experiments was carried out to identify the 25~o daughter, an alpha particle emitter with an energy Qf 8.01 MeV and a haU':'life of 105 seconds. 4,9 After a period of 200 seconds during which the 257104 alpha activity was measured, the four crystal detectors were automatically shuttled to positions opposite four similar detectors. This was done in order to measure the activity at high geometry from the daughter atoms which had been transferred by alpha pa~ticle recoil to the detectors when they were opposite the wheel. During the next 200 second period it was then possible to measure the half-life and energy of the daughter atoms free from the interference produced by those atoms produced directly during the bombardment. This cycle was repeated automatically with the beam being turned off during the daughter-measuring intervals. A composite spectrum of the mother and daughter activities is shown in Fig. 3e The activity from the 55-sec 8.10 MeV 254NO which was produced directly in good yield during the bombardment served to monitor the amount of nobelium that reached the surfaces of the crystals by a transfer mechanism of unknown origin; such trans-ferrednobelium atoms were observed only in the first detector. The amount of 253No daughter activity, as well as its energy and half-life, correspond qui te well with the genetic sequence proposed. Bombardments with i3C ions of the 249Cf target produced a somewhat similar activity but it was possible to differentiate it from the 257104 in several ways: (1) The complex alpha particle spectrum consists of two prominent groups with energies 8.77 and 8.86 MeV, and relative intensities 0.6 and 0.4, respectlvely: (2) the half-life is somewhat shorter and our best value so far is 8 about 3 seconds; and (3) the excitation function and cross section correspond 13 259 much more 'closely to those of the C,3n reaction to make 104 than that of ~.- " .. -4- UCRL-18819 the 13C,5n reaction to make 2571040 Further evidence for the assignment to the former nuclide was obtained when the same type of daughter-measuring experiment as in the case of 257104 was carried out. A known isotope of nobelium, the 185-sec 8.11 MeV 255No 4,10 was identified as the alpha recoil product experiments. More recently we have produced the 3-second 104259 reaction in bombardments of 248Cm• in these 16 by the O,5n Spontaneous fission branching decay was not found to be prominent for either one of these nuclides but in a different type of experiment we did uncover a new fission period which is probably due to 2581040 We used an t 11 "t" f d t t" t t th t t" t t h appara us conSlS lng 0 a rum ro a lng nex 0 e arge In vacuum 0 ca c the transmutation reCOils directly. A peripheral series of mica detectors was placed to record the passage of fragments from spontaneous fission; after suitable 12 etching the ir tracks could be 0 bse rved opti cally. The rotating drum was moved transversely to the direction of the beam to spread out the longer-lived ftssionactivities and thus reduce the background. The speed of the drum was such that a 1 millisecond period could be easily measured. An activity with 249 a half-life of 11 ± 2 milliseconds was observed when the Cf target was bom-barded by both 12C and 13C ions. Its excitation functions and yields are con-258 12 13 sistent with its·being assigned to 104 made by the C,3n and C,4n reactions and the half-life compares favorably with the 4 ms predicted by our empirical systematics. 5,11 Even though we have observed thousands of spontaneous fission events, because of the prevalence of isomers in the heavy element region which undergo this type of decay, we still are not certain of the correctness of this attribution. On the other hand, according to Nilsson,13 the appearance of spontaneous fission isomers in this particular region of Z values is unlikely. We gratefully acknowledge the very considerable assistance afforded by the following people in making these experiments possible.: R. Mo Latimer. in the chemical processing of the target material; C. A. Corum and the Mechanical i -5- UCRL-188l9 Technicians at the HILAC for the design and fabrication ~f the apparatus; A. E. Larsh and A: A. Wydler for the electronic hardware used; R. G. Leres and D. F. Lebeck for the .advanced c~mputer software solutions; F. S. Grobelch and the HlLAC operators for the excellent performance of the accelerator; ~nd P. Shaw and C. Jung, our patient mica scanners. We appreciate the very important help in the initial stages by To Sikkeland and are very pleased by the interest and encouragement shown to us by G. T. Seaborg. One of the authors, P. Eskola, is indebted to the National Research Council for SCiences, Helsinki, Finland, for financial supporto -.6- UCRL-18819 FOOTNOTES AND REFERENCES * This work was done under the auspices of the Atomic Energy Commission. tOn leave of absence from Department of Physics, University of Helsinki, Finland. *Guest Scientist supported by the Na~ional Research Council of Sciences, Helsinki, Finland. 1. Ao Ghiorso, M" Nurmia, J. Harris, Lawrence Radiation Laboratory Report UCRL-18714, 1969 (unpublished). 2. G. N. Flerov, YUo Tso Oganesyan, YUo V. Lobanov, V. I. Kuznetsov, V. A. Druin, 3· V. P. Perelygin, K. Ao Gavrilov, S. P. Tretiakova, V. M. Plotko, Ato Energ. (USSR) 17, 310 (1964)(Soviet J. At. Energy 17, 1046 (1964), translated from Russian); Phys. Letters 13, 73 (1964). 249 The target material 'Was milked from several hundred micrograIllB of Bk at the TRU facility at ORNL by D. Ferguson et ala, to whom we would like to express our gratitude. 40 A. Ghiorso, T. Sikkeland, M. J. Nurmia, Phys. Rev. Letters 18,401 (1967). 5. A. Ghiorso, T. Sikke land , Physics Today?Q, 25 (1967). 6. Manufactured by ORTEC-. 7. J. T. Routti, S. G. Prussin, Lawrence Radiation Laboratory Report UCRL-17672, Dec. 1968 (unpublished). 8. T. Sikkeland and D. F. Lebeck, unpublished work. 9. v. L. Mikheev, V. I. Ilyushchenko, M. B. Miller, S. M. Polikanov, G. N. Flerov, Yu. P. Kharitonov, At. Energo (USSR) 22, 90 (1967) (Soviet J. At. Energy 22 93 (1967), translated from Russian). 10. G. N. Flerov, S. M. Polikanov, V. L. Mikheev, V. I. I lyushchenko, V. F. Kushniruk, M. B. Miller, A. M. Sukhov, Vo A. Shchego1ev, Yadern. Fiz. 2, 1186 (1967) (Soviet J. Nuc1. Phys. 2; 848 (1967). 11. M. Nurmia, K. Esko1a, P. Esko1a, A. Ghiorso, Lawrence Radiation Lab8ratory " ~7- UCRL-18819 FOOTNOTES AND REFERENCES (continued) • Report UCRL-18712, 1969 (unpublished). 12. P. B. Price and R. M. Walker, Phys. Rev. Letters }, 113 (1962). S. G. Nilsson, Lawrence Radiation Laboratory Report UCRL-18355 Rev., Sept. 1968 (unpublished). -8- UCRL-18819 FIGURE CAPTIONS Fig. 1. A series of alpha spectra of the activities produced by bombardment 249 12 . of Cf with 71-MeV C wns. The top spectrum is the sum of the indi vi-dual spectra from the four detectors. The 8.60 MeV peak is probably due to 2 58Lrj the peaks above that energy belong to 257104 with the exception of the one at 8.87 MeV whose origin is uncertain. Fig. 2. Excitation curves of several acti vi ties produced by bombardment of 249Cf with 12C ions. Note the high yield of the nobelium isotopes 12 produced in C,axn reactions. There is an uncertainty in the energy scale tha t could be as much as 5 Me V. Fig. 3. A set of spectra from the mother-daughter experiment which demonstrates the genetic relationship between 257104 and 25~o. The spectra recorded. by the individual crystal pairs are shown on top with the sum of the last three pairs at the bottom. • OJ C ·c. ro .r:. c..> OJ a. (,/) ........ C ::J o U 80 60 40 20 I;"" 1 x 1000 209R 210R n+ n 6.04:3 214 Ra 7136 252~m 7.04 -9-250Fm 7.43 254No+255NO· 8.10 x_l_ 20 Channe I number' UCRL-18819 x1 8.95 8.87 8.60 9.00 XBL6944816 2. 3. . · -10- UCltL-18819 c: 0 ..... u Q) 103 cfl cfl cfl 0 ~54NO "-u Q) 255No > ..... 253No (\J Q) a::: 102 256No 10 lL-----~--~~--~----~----~----~----~ 60 70 80 90 100 110 Energy (MeV) XBL6944815 Fig. 2 -11- UCRL-18819 Mother Daughter 40 40 30 30 20 10 1. 0 20 20 10 2. 0 20 20 (jj c::: ~ 10 10 ..c::: u 3. 0 rJ) ... c::: ::J 020 20 (J 10 4. 0 30 20 20 10 .' 2.+3.+4. 7.9 8.2 J Energy (MeV) XBL 6944813 Fig. 3 : i LEGAL NOTICE This report was prepared as an account of Government sponsored work. Neither the United States, nor the Commission, nor any person acting on behalf of the Commission: A. Makes any warranty or representation, expressed or implied, with respect to the accuracy, completeness, or usefulness of the informa-tion contained in this report, or that the use of any information, apparatus, method, or process disclosed in this report may not in-fringe privately owned rights; or B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of any information, apparatus, method, or process disclosed in this report. As used in the above, "person acting on behalf of the Commission" includes any employee or contractor of the Commission, or employee of such contractor, to the extent that such employee or contractor of the Commission, or employee of such contractor prepares, disseminates, or pro-vides access to, any information pursuant to his employment or contract with the Commission, or his employment with such contractor. ~~~S' TECHNICAL INFORMA TION DIVISION LAWRENCE RADIATION LABORATORY UNIVERSITY OF CALIFORNIA BERKELEY, CALIFORNIA 94720 --~' ~;...  -JI' 

POSITIVE IDENTIFICATION OF TWO ALPHA PARTICLE EMITTING ISOTOPES OF ELEMENT 104

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