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The isotopic distribution of nuclei produced in the 50Ti + 249Cf reaction has been studied at the gas-filled recoil separator TASCA at GSI Darmstadt, which separates ions according to differences in magnetic rigidity. The bombardment was performed at an energy around the Bass barrier and with the TASCA magnetic fields set for collecting fusion-evaporation reaction products. Fifty-three isotopes located “north-east” of 208Pb were identified as recoiling products formed in non-fusion channels of the reaction. These recoils were implanted with energies in two distinct ranges; besides one with higher energy, a significant low-energy contribution was identified. The latter observation was not expected to occur according to kinematics of the known types of reactions, namely quasi-elastic, multi-nucleon transfer, deep-inelastic collisions or quasifission. The present observations are discussed within the framework of two-body kinematics passing through the formation of a composite system.

The isotopic distribution of nuclei produced in the 50Ti + 249Cf reaction has been studied at the gas-filled recoil separator TASCA at GSI Darmstadt, which separates ions according to differences in magnetic rigidity. The bombardment was performed at an energy around the Bass barrier and with the TASCA magnetic fields set for collecting fusion-evaporation reaction products. Fifty-three isotopes located “north-east” of 208Pb were identified as recoiling products formed in non-fusion channels of the reaction. These recoils were implanted with energies in two distinct ranges; besides one with higher energy, a significant low-energy contribution was identified. The latter observation was not expected to occur according to kinematics of the known types of reactions, namely quasi-elastic, multi-nucleon transfer, deep-inelastic collisions or quasifission. The present observations are discussed within the framework of two-body kinematics passing through the formation of a composite system.

To identify the atomic number of superheavy nuclei produced in 48Ca-induced fusion-evaporation reactions, an experiment aiming at measuring characteristic X-rays is being prepared at GSI, Darmstadt, Germany. The gas-filled separator TASCA will be employed, sending the residues towards the multi-coincidence detector setup TASISpec. Two ionoptical modes relying on differing magnetic polarities of the quadrupole magnets can be used at TASCA. New simulations and experimental tests of transmission and background suppression for these two focusing modes into TASISpec are presented.

To identify the atomic number of superheavy nuclei produced in 48Ca-induced fusion-evaporation reactions, an experiment aiming at measuring characteristic X-rays is being prepared at GSI, Darmstadt, Germany. The gas-filled separator TASCA will be employed, sending the residues towards the multi-coincidence detector setup TASISpec. Two ionoptical modes relying on differing magnetic polarities of the quadrupole magnets can be used at TASCA. New simulations and experimental tests of transmission and background suppression for these two focusing modes into TASISpec are presented.

The deformed doubly magic nucleus Hs270 has so far only been observed as the four-neutron (4n) evaporation residue of the reaction Mg26+Cm248, where a maximum cross section of 3 pb was measured. Theoretical studies on the formation of Hs270 in the 4n evaporation channel of fusion reactions with different entrance channel asymmetry in the framework of a two-parameter Smoluchowski equation predict that the reactions Ca48+Ra226 and S36+U238 result in higher cross sections due to lower reaction Q values, in contrast to simple arguments based on the reaction asymmetry, which predict opposite trends. Calculations using hivap predict cross sections for the reaction S36+U238 that are similar to those of the Mg26+Cm248 reaction. Here, we report on the first measurement of evaporation residues formed in the complete nuclear fusion reaction S36+U238 and the observation of Hs270, which is produced in the 4n evaporation channel, with a measured cross section of 0.8-0.7+2.6 pb at 51-MeV excitation energy. The one-event cross-section limits (68% confidence level) for the 3n, 4n, and 5n evaporation channels at 39-MeV excitation energy are 2.9 pb, while the cross-section limits of the 3n and 5n channel at 51 MeV are 1.5 pb. This is significantly lower than the 5n cross section of the Mg26+Cm248 reaction at similar excitation energy. © 2010 The American Physical Society.

The deformed doubly magic nucleus Hs270 has so far only been observed as the four-neutron (4n) evaporation residue of the reaction Mg26+Cm248, where a maximum cross section of 3 pb was measured. Theoretical studies on the formation of Hs270 in the 4n evaporation channel of fusion reactions with different entrance channel asymmetry in the framework of a two-parameter Smoluchowski equation predict that the reactions Ca48+Ra226 and S36+U238 result in higher cross sections due to lower reaction Q values, in contrast to simple arguments based on the reaction asymmetry, which predict opposite trends. Calculations using hivap predict cross sections for the reaction S36+U238 that are similar to those of the Mg26+Cm248 reaction. Here, we report on the first measurement of evaporation residues formed in the complete nuclear fusion reaction S36+U238 and the observation of Hs270, which is produced in the 4n evaporation channel, with a measured cross section of 0.8-0.7+2.6 pb at 51-MeV excitation energy. The one-event cross-section limits (68% confidence level) for the 3n, 4n, and 5n evaporation channels at 39-MeV excitation energy are 2.9 pb, while the cross-section limits of the 3n and 5n channel at 51 MeV are 1.5 pb. This is significantly lower than the 5n cross section of the Mg26+Cm248 reaction at similar excitation energy. © 2010 The American Physical Society.

The deformed doubly magic nucleus Hs270 has so far only been observed as the four-neutron (4n) evaporation residue of the reaction Mg26+Cm248, where a maximum cross section of 3 pb was measured. Theoretical studies on the formation of Hs270 in the 4n evaporation channel of fusion reactions with different entrance channel asymmetry in the framework of a two-parameter Smoluchowski equation predict that the reactions Ca48+Ra226 and S36+U238 result in higher cross sections due to lower reaction Q values, in contrast to simple arguments based on the reaction asymmetry, which predict opposite trends. Calculations using hivap predict cross sections for the reaction S36+U238 that are similar to those of the Mg26+Cm248 reaction. Here, we report on the first measurement of evaporation residues formed in the complete nuclear fusion reaction S36+U238 and the observation of Hs270, which is produced in the 4n evaporation channel, with a measured cross section of 0.8-0.7+2.6 pb at 51-MeV excitation energy. The one-event cross-section limits (68% confidence level) for the 3n, 4n, and 5n evaporation channels at 39-MeV excitation energy are 2.9 pb, while the cross-section limits of the 3n and 5n channel at 51 MeV are 1.5 pb. This is significantly lower than the 5n cross section of the Mg26+Cm248 reaction at similar excitation energy. © 2010 The American Physical Society.

The angular momenta and parities of the low lying states of Sn-132 have been firmly determined through studies of the beta-decay of In-132. The lowest lying state with a negative parity is shown to have a collective octupole character. Several particle-ho, Addresses: FOGELBERG B, UNIV UPPSALA, DEPT NEUTRON RES, S-61182 NYKOPING, SWEDEN. UNIV OSLO, DEPT CHEM, N-0315 OSLO, NORWAY. ROYAL INST TECHNOL, DEPT PHYS, S-10405 STOCKHOLM, SWEDEN.

A measurement of B(E3) in the two-proton nuclide Te-134 was made, giving the first empirical value of the effective proton octupole charge in the neutron rich doubly closed shell region at Sn-132. It is demonstrated that the effective E2 and E3 charges ca, Addresses: OMTVEDT JP, UNIV OSLO, DEPT CHEM, POB 1033 BLINDERN, N-0315 OSLO, NORWAY. UNIV UPPSALA, DEPT NEUTRON RES, S-61182 NYKOPING, SWEDEN. RUSSIAN ACAD SCI, AF IOFFE PHYSICOTECH INST, ST PETERSBURG 194021, RUSSIA. RUSSIAN ACAD SCI, ST PETERSBURG NUCL

Addresses: MACH H, UPPSALA UNIV, DEPT NEUTRON RES, S-61182 NYKOPING, SWEDEN. UNIV OSLO, DEPT CHEM, N-0315 OSLO, NORWAY. AF IOFFE PHYS TECH INST, ST PETERSBURG 194021, RUSSIA. ST PETERSBURG NUCL PHYS INST, GATCHINA 188350, RUSSIA.

Experimental studies at the OSIRIS fission-product mass separator have yielded a wealth of new results on the doubly-magic region near Sn-132. In the following we focus on two aspects of the new results: on the evidence for octupole collectivity of the 3(, Addresses: MACH H, UNIV UPPSALA, DEPT NEUTRON RES, S-61182 NYKOPING, SWEDEN. ROYAL INST TECHNOL, DEPT PHYS FRESCATI, S-10405 STOCKHOLM, SWEDEN. UNIV OSLO, DEPT CHEM, N-0315 OSLO, NORWAY. RUSSIAN ACAD SCI, AF IOFFE PHYSICOTECH INST, ST PETERSBURG 194021, R