PL9601122 PL9601121 High-Spin Nuclear Target of 178m2Hf: Creation and Nuclear Reaction Studies Yu. Ts. Oganesian1, S.A. Karamian1, Yu. P. Gangrsky1, B. Gorski1, B.N. Markov1, Z. Szeglowski2, Ch. Briangon3, O. Constantinescu3, M. Hussonnois3, J. Pinard3, R. Kulessa4, H.J. Wollersheim4, G. Graw5, J. de Boer5, G. Huber6 and H.V. Muradian7 XFLNR, JINR Dubna, Russia; 2H. Niewodniczanski Institute Nuclear Physics, Krakow, Poland; 3CSNSM, IPN, Orsay, France; 4GSI, Darmstadt, Germany; 6Miinchen University, Germany; 6Mainz University, Germany; 7Kurchatov Institute, Moscow, Russia. Investigations of the hafnium-178 isomers are a new scientific direction promising the devel- opment of a fundamental knowledge both in the field of the nuclear structure and of nuclear reactions. The completed experiments give grounds for hope of obtaining data on the electro- magnetic moments, on the mean radius and the deformation of the 178Hf nucleus in the state 16+, on the wave function structure of this state, as well as to study the influence of the target high spin on the differential cross sections of nuclear reactions, to find and investigate neutron resonances with a high spin, to obtain direct information on the density of the levels in the earlier inaccessible region of the spin and of the excitation energy, to measure directly the parameters of a giant dipole resonance based on the high spin state and to clarify in detail the role of the structure hindrances in nuclear reactions. Sorption Behaviour of Short-Lived W and Hf Isotopes on Ion Exchangers from HC1/HF Solutions in Fast On-Line Experiments D. Schumann1, R. Dressier1, S. Fischer1, St. Taut1, R. Binder2, Z. Szeglowski3, B. Kubica3, L.I. Gusieva4, G.S. Tikhomirova4, 0. Constantinescu5, G.I. Buklanov5, V.P. Domanov5, M. Constantinescu5, Dinh Thi Lien5, A. Jakushev5, Yu.Ts. Oganessian5, I. B. Brudanin6, A.F. Novgorodov 6 and H. Bruchertseifer7 *FG Radiochemie, Institut fur Analytische Chemie, Technische Universitat, FRG; 2Kern- und Radiochemie Leipzig, FRG; 3H. Niewodniczanski Institute of Nuclear Physics, Krakow, Poland; institute of Geochemistry and Analytical Chemistry RAN, Moscow, Russia; laboratory of Nuclear Reactions, JINR Dubna, Russia; 8Laboratory of Nuclear Problems, JINR Dubna, Russia; 7PSI Villigen, Switzerland. Introduction The 4-6 subgroups of elements are suitable tracers to investigate the chemical properties of the heavy elements 104-106. The main problem in this field is the fast separation of these elements from all other nuclides produced in heavy ion reactions. Previous works showed that the separation of W from Hf and lanthanides in mixed solutions of HC1 and HF at low concentrations can be carried out using the ion exchange method. It was shown that W can be completely separated from Hf by adsorbing the latter on Dowex 50X8 using 0.05 M HC1 / 10"3M HF solution. First on-line experiments at the TRIGA reactor in Mainz showed that Mo can be completely separated from the lanthanides, Zr and Nb by using the degasser from the SISAK system and separation columns filled with cation exchanger. In the present work we tested these conditions in fast one-line separations using heavy ion reactions at the U-400 cyclotron (Laboratory of Nuclear Reactions JINR Dubna, Russia). Experimental Short lived isotopes of tungsten and hafnium were produced via the following heavy ion reactions: 255 i47,i49Sm + 2oNe __> Hf (95-98 MeV) 152,154,158Qd + 20Ne _^ W (96 MeV) at the U-400 cyclotron. The recoiled atoms were transported from the target chamber using a KCl/Ar gas jet (1 1/min). The equipment for the separation experiments has been described earlier. Columns (20 X 3 mm) were filled with Dowex 50X8 or Dowex 1X8 (240 mesh) and preequilibrated for 12 hours. All separation experiments were performed with the mixture of 0.05 M HC1 and 10 ~3M HF using flow rates of 1-3 ml/min. The measurements were performed using a high resolution HPGeX detector (ORTEC) and a HPGe-PT detector (ORTEC). Results and Discussion 1. Tungsten The main products of the nuclear reaction were mW (2.38 min), 170W (2.42 min), 169W (1.27 min) and 168W (53.2 s) produced in the 3n and 4n reaction channel, respectively. l74W (29 min.) and mW (34 min.) could not be detected due to their relatively long half-life. The results of the separation using the 0.05 M HC1 / 10"3M HF solution are shown in Fig.l. It can be seen that all four W isotopes are found on Dowex 1X8 (171W: 294,8 keV, 170W: 316.2 keV, 124.7 keV, 169W: 136.8 keV, 168W: 178.8 keV). These peaks cannot be found after the separations on Dowex 50X8. Some peaks from these W isotopes can be observed on the cation exchanger too, but they are overlapped with those of other nuclides for example: mW/168Hf - 183.7 keV. Therefore, the conclusion can be drawn that W can be completely separated in the described way, as had already been expected from previous studies. 100 150 200 250 300 350 400 450 500 2500- DOUEN 1X8 2000- 1300- f 9 1000- "' ' a ? 500- 100 150 200 250 300 350 400 450 500 trwrgy | k«V ] Figure 1: 7-Spectra of the Dowex 50X8 and Dowex 1X8 columns: nuclear reaction: i52,i54,i58Gd + 20Ne -* W; solution: 0.05 M HC1 / 10"3 M HF. 256 PL9601123 200 2SO 300 anwgy (kav ] Figure 2: 7-Spectra of the Dowex 50X8 and Dowex 1X8 columns: nuclear reaction: 147-149Sm + 20Ne -» Hf solution: 0.05 M HC1 / 10~3 M HF. 2. Hafnium As can be seen from Fig.2 the main reaction products 166Hf (1.25 min.) and 186Hf (6.77 min.) can be found on Dowex 50X8. Only small peaks of 165Hf (179.9 keV) and 166Hf (228.0 keV) are observed on the anion exchange column. The calculation shows that 99% of Hf is adsorbed on the cation exchanger while Lu is completely adsorbed on this column. Summary The results show that in the described system of cation and anion exchange columns with 0.05 M HC1 / 10~3M HF solution tungsten can be separated from nearly all other elements produced in heavy ion reactions, mainly from lanthanides and hafnium. Consequently, the developed system should be applicable for fast on-line separations of the element 106. Ion Exchange Behaviour of Zirconium and Hafnium as Homologues of 104 Element in Phosphoric Acid Solutions Z. Szeglowski1, L.I. Guseva2, Din Thi Lien3, V.P. Domanov3, O. Constantinescu3, G.S. Tikhomirova2 and M. Hussonnois4 XH. Niewodniczanski Institute of Nuclear Physics, Krakow, Poland; institute of Geoche- mistry and Analitycal Chemistry RAN, Moscow, Russia; 3Laboratory of Nucleai Reactions, JINR, Dubna, Russia; 4IPN, Orsay, France. The distribution coefficient of Zr, Hf, Sr and some actinide and lanthanide elements between ion exchange resins and phosphoric acid solutions were determined. The optimum conditions for the concentration and separation of Zr(Hf) from the trivalent actinides in H3PO4 - ion exchange resins systems have been found. The high decontamination factor (>106) of hafnium from europium was obtained using the Dowex 50 resin in 0.5 M H3PO4 solution. In the conditions imitating the isolation of element 104 257.