ERRATA to the thesis Separation and study of nuclides far from beta stability and search for new regions of nuclear stability Magne Skarestad Location Is written Should be Review paper,p.2 missing SISAK=Short-lived Lsotopes footnote .Studied by Akufve techniqu Paper I,p.2400 detector 1 and 2 1.7 from bottom detector 2 and 1 Paper II,p.1695 H.F.O, Lawrence ref.8 F.O. Lawrence Paper II,p.1695 Borg,S., Rydberg.B.,... Borg,S., Bergstrom.I., ref.11 Rydberg,B.,... Paper IV,p,76i 1365.6 table 4. last line 1356.6 Paper VII,p.271 to note that this 1.3 in 2.column to note that the Paper VII,p.271 the simple decay 1,15 in 2.column the simple delay Paper VII,p.271 eq.(2) Paper VII,p.271 eq.(3) Paper VII,p.271 D/r2 fig. 6 Paper VII,p.271 Kcal kcal/mol fig. 6 1 3 3 Paper VII,p.271 y-axis, 100" »10" y-axis, 10" fig. 6 faptr X,p.U7 1 mg/om*d 1 mg/oni *d (ill) Paper X,p.i53 30 nT is shown 30p I are shown 1.2 from bottom SEPARATION AND STUDY OF NUCLIDES FAR FROM BETA STABILITY AND SEARCH FOR NEW REGIONS OF NUCLEAR STABILITY BY MAGNE SKARESTAD 1977 UNIVERSITY OF OSLO, DEPARTMENT OF CHEMISTRY, OSLO, NORWAY CONTENTS: Preface List of papers Review 1. Introduction 2. SISAK 2.1 The experimental technique 2.2 Study of short-lived, neutron-rich rare-earth isotopes 3. ISOLDE 3.1 Development of target systems 3.2 On-line atomic-beam magnetic resonance (ABMR) measurements 3.3 ABMR results k. Superheavy elements b.l Production in secondary reactions ^.2 Chemical separation schemes 5. Perspectives ... „ ...yfeu PREFACE The present work consists of a review and thirteen papers, based on experiments carried out at the University of Manchester, Rutherford Laboratory, University of Oslo, University of Mainz and CERN during the period 1971-1976. It is with great pleasure I thank all my collaborators for for excellent co-operation in the various investigations '' concerned. In particular, I am indebted to Dr. G.W.A. Newton, Dr. C.J. Batty, professor P.G. Hansen and Dr. C. Ekstrflm for ( the opportunity to participate in their inspiring research groups. It is also a pleasure to acknowledge professor G. Hermann, who kindly made the experimental facilities available at the Institut filr Kernchemie, Mainz. Special thanks are due to professor A.C. Pappas, who introduced me to the field of nuclear science, for his continuous support and good advice on numerous occasions. •-&.. ...yfc.- LIST OF PAPERS The present work includes the following series of papers, referred to with roman numerals I-XIII in the accompanying review: I. P.O. Aronsson, B.E. Johansson, J. Rydberg, G. Skarnemark, J. Alstad, B. Bergersen, E. Kvale and M. Skarestad: SISAK - a new technique for rapid, continuous (radio)- chemical separations. J. Inorg. Nucl. Chem. £6. (1974) 2397. II. P.O. Aronsson, G. Skarnemark and M. Skarestad: Short-lived isotopes of lanthanum, cerium and praseodymium studied by SISAK-technique. J. Inorg. Nucl. Chem. _3_6 (1974) 1689. III. P.O. Aronsson, G. Skarnemark and M. Skarestad:... The half-life o-fr*50Ce obtained by SISAK-technique. """ : Inorg. Nuc'l.'Chem. Letters 10 (1974) 499". IV. P.O. Aronsson, G. Skarnemark, E. Kvale and M. Skarestad: Decay characteristics of some neutron-rich lanthanide nuclides obtained by SISAK-technique. •Inorg. Nucl. Chem. Letters 1£ (1974) 753. V. JfC Trautmann, P.O. Aronsson, T. Bj^rnstad, N. Kaffrell, E. Kvale, M. Skarestad, G. Skarnemark and E. Stender: The combination of the gas jet recoil technique with fast chemical on-line separation system SISAK. Inorg. Nucl. Chem. Letters 11 (1975) 729. VI. L.C. Carraz, I.R. Haldorsen, H.L. Ravn, M. Skarestad and L. Westgaard: Fast release of nuclear reaction products from refractory matrices. Nucl. Instr. Meth. JL4_8 (1978) 217. VII. H.L. Ravn, L.A. Carraz, J. Denimal, E. Kugler, M. Skarestad, S. Sundell and L. Westgaard: ' New techniques at ISOLDE-2. • Nucl. Instr. Meth. 139_ (1976) 267. VIII. J.M. D'Auria, L.C. Carraz, P.G. Hansen, B. Jonson, S. Mattsson, H.L. Ravn, M. Skarestad and L. Westgaard: The N=Z nuclide 7"Rb with 1,1* = l,0+ . Phys. Lett. 6_6B (1977) 233. IX. C. Ekstrflm, S. Ingelman, G. Wannberg and M. Skarestad: Atomic-beam measurements of nuclear spins at ISOLDE, CERN. CERN Report 76-13 (1976) 193. X. C. EkstrSm, S. Ingelnin, G. Wannberg and M. Skarestad: Hyperfine structure, nuclear spins and magnetic moments of some cesium isotopes. Nucl. Phys. A292 (1977) 144. XI. C. EkstrSm, S. Ingelman, C. Wannberg and M. Skarestad: Nuclear spin measurements in some nuclides of the alkali elements rubidium and francium. University of Uppsala, Institute of Physics Report, UUIP-954 (1977). XII. C.J. Batty, A.I. Kilvington, J.L. Weil, G.W.A. Newton, M. Skarestad and J.D. Hemmingway: Search for superheavy elements and actinides produced by secondary reactions in a tungsten target. Nature 244, 5416 (1973) 429. XIII. G.W.A. Newton, V.J. Robinson, M. Skarestad and J.D. Hemmingwa; The chemical separation of some heavy elements from proton irradiated tungsten. J. Inorg. Nucl. Chem. 3J3. (1973) 2035. REVIEW PAPER •••»-,. -1- In the past decade the study of the "sea of instability" surrounding the stable nuclides which form a peninsula in the N,Z diagram (Fig. 1), has developed into a major field of research. In this period, the "off-shore" research has led to the observation of new phenomena, the domain of observed nuclides has been enlarged and detailed properties of a large number of nuclides, in the ground state as well as in excited states, have been studied (1 ' 2 ' 3). In the same period a frantic search for a new island of (near) stability has been going on. According to theoreticians, the island is situated around 2 9 8114 where the disruptive coulombic forces are expected to become out-balanced by stabilizing shell effects. The search for these superheavy nuclei has included attempts to produce them artificially as well as attempts to find them in nature. The extention of the range of experiments has been possible because of the development in experimental techniques. New and more intense beams of bombarding particles have become available, new types of measuring methods have been developed and "old" methods have been adapted to new facilities. Last, but not least, we have seen some decisive progress in the development of product separation methods which aim at providing isotopica.lly. pure samples for physics experiments, on a short time-scale and in high efficiency. In recent years a number of new separation approaches have been realized like the electric and magnetic field separator LOHENGRIN , the gas-filled magnetic separator JOSEF and the kinematic separator SHIP . These systems are all characterized by very short separation times (a* 10 s), but the efficiency -2- is rather low (10~ - 10" ). An exception is the .kinematic separator which may work with efficiencies in the percent region. In this case, however, only fusion products are separated. Selectivity in both atomic number (Z) and mass number (A), is achieved in all systems, although the resolution is limited. In addition to these new approaches, progress has been made in bringing the more conventional approaches of radiochemical separations and electromagnetic mass separation up to a standard which meets the present and future demands. A large part of the present work concerns the progress in this area. In radiochemical separations, progress has been made in developing both discontinuous and continuous separation techni- (7 8) ques ' . Outstanding examples of fast, discontinuous (a) separations have been reported from the University of Mainz , where chemical separations are performed on a subsecond time scale. However, when experiments have to be performed repeatedly, a continuous separation process delivering a steady source of short-lived species is more appropriate. Such separations are accomplished in the on-line operating solvent extraction system SISAK . The combination of this separation technique with a Gas Jet Recoil Transport (GJRT) system makes it possible to adapt the separation system to different irradiation facilities(V) The performance of SISAK has been illustrated through the study of short-lived rare-earth isotopes, using conventional y- ray spectroscopy . A summary is given in chapter 2. In chemical separations, a selection in Z but not in A, is achieved. At most on-line isotope separator facilities, the situation is the other way around. A separation in A is readily CTCAV - Ton-t-nn©<= RttiriieH hv AViifvp. +echniaue -3- 100 • Z 6O- 169 ISO Fig. 1. The chart of nuclides. The domain of known nuclides is enclosed by the broken contour, the black' squares representing stable nuclides. The proposed island of superheavy nuclei, enclosed by the dashed contour and marked with SHE, contains those nuclei which according to Nix^59^ have half-lives longer than 1 day. obtained, while sufficient selectivity in Z in many cases is hard to reach. Still, progress in delivering beams of single elements is being made by proper choices of target matrices and ion-source configurations . Selective on-line thermo- chromatographic separations of some product elements, following mass separation, have also been demonstrated^11^. Apart from selectivity, progress is also made in enlarging the range of available product elements as well as in reducing the delay inherent in the target systems. At ISOLDE an extensive investi- gation of refractory materials in porous form at high temperatures, showed that a number of these matrices have very favourable delay-time'characteristics(VI). The nost promising matrices have been tested on-line with good results(VII "v:!:iI).