Spin depending angular anisotropy of the alpha-decay and spontaneous fission of oriented transuranium nuclei

G.M.Gurevich1, A.L.Erzinkyan2, P.-D.Eversheim3, V.T.Filimonov4 , V.Golovko5, P.Herzog3, I.Kraev5, A.A.Lukhanin6, A.A.Belyaev6, V.I.Noga6, V.P.Parfenova2, T.Phalet5, A.V.Rusakov1, N.Severijns5, Yu.G.Toporov4, V.N.Vyachin7, D. Zakoucky8

1Institute for Nuclear Research, Russian Academy of Sciences, Moscow, Russia

2Institute of Nuclear Physics, Moscow State University, Moscow, Russia

3Bonn University, Bonn, Germany

4Research Institute for Atomic Reactors, Dimitrovgrad, Russia

5Leuven University, Leuven, Belgium

6Kharkov Institute of Physics and Technology, Kharkov, Ukraine

7All-Russian Scientific Research Institute of Experimental Physics, Sarov, Russia

8Nuclear Research Institute, Rez, Czech Republik

Two main objectives of this research project are: 1) to investigate a relation between the angular anisotropy of the alpha emission of oriented 241,243Am, 253,255Es, 255,257Fm nuclei and their nuclear deformation, and 2) to obtain first precise data on the quantum numbers of fission channels from the spontaneous fission anisotropy of oriented 255Es and 257Fm nuclei. The low temperature nuclear orientation (LTNO) technique is used to measure angular distribution of charged fragments. Samples for the experiment were prepared using the ion implantation of transuranium isotopes into specially prepared iron foils. Pure 241Am and 243Am sources were prepared at the electromagnetic isotope separator in Sarov which was modified to perform ion implantation. Es and Fm activities were prepared by neutron irradiation of curium targets in high flux nuclear reactor (1.5´ 1015 neutrons/cm2s) with subsequent radiochemical separation and purification of accumulated Es and Fm. This activity was used to prepare sources for LTNO experiments containing 253,254,255Es and 255Fm by ion implantation at the Bonn isotope separator. First measurements of the alpha emission angular anisotropy in the temperature range 40 - 1000 mK were performed using 3He - 4He dilution refrigerator in combination with charged fragment detectors (Si PIN diodes) working at 4.2 K. 54Mn(Ni) nuclear orientation thermometer was used to measure an absolute temperature. The data on the angular distribution in favoured a -decay of 253Es and 255Fm (daughter isotope of 255Es) were extracted from the measurements and are being analysed now.