[en] Thulium(III) oxide (Tm₂O₃) targets prepared by the polymer-assisted deposition (PAD) method were irradiated by heavy-ion beams to test the method's feasibility for nuclear science applications. Targets were prepared on silicon nitride backings (thickness of 1000 nm, 344 (micro)g/cm²) and were irradiated with an ⁴⁰Ar beam at laboratory frame energy of ∼210 MeV (50 particle nA). The root mean squared (RMS) roughness prior to irradiation is 1.1 nm for a ∼250 nm (∼220 (micro)g/cm²) Tm₂O₃ target, and an RMS roughness of 2.0 nm after irradiation was measured by atomic force microscopy (AFM). Scanning electron microscopy of the irradiated target reveals no significant differences in surface homogeneity when compared to imaging prior to irradiation. Target flaking was not observed from monitoring Rutherford scattered particles as a function of time

[en] The new isotope 178Tl was produced in a bombardment of 102Pd by 78Kr ions at 340 MeV. Reaction products were separated from the beam by the Berkeley Gas-Filled Separator and implanted into a silicon strip detector where the subsequent alpha decays were measured. Four distinct alpha transitions from 178Tl were observed correlated to 6.54 MeV alpha decays from the previously known 174Au daughter. In some cases, the 174Au decay was followed by a 5.815 MeV alpha decay. This new transition is tentatively assigned to the decay of the 170Ir ground state. The half-life of 178Tl was measured to be 254 ms. The alpha decay branch of 174Au was determined to be 90(6) percent

[en] Excitation functions for the 1n and 2n exit channels of the 208Pb(51V,xn)259-xDb reaction were measured. A maximum cross section of the 1n exit channel of 2070+1100/-760 pb was measured at an excitation energy of 16.0 +- 1.8 MeV. For the 2n exit channel, a maximum cross section of 1660+450/-370 pb was measured at 22.0 +- 1.8 MeV excitation energy. The 1n excitation function for the 209Bi(50Ti,n)258Db reaction was remeasured, resulting in a cross section of 5480+1750/-1370 pb at an excitation energy of 16.0 +- 1.6 MeV, in agreement with previous values [F. P. Hebberger, et al., Eur. Phys. J. A 12, 57 (2001)]. Differences in cross section maxima are discussed in terms of the fusion probability below the barrier

[en] Electron-capture delayed fission was observed in ²⁴⁴Es produced via the ²³⁷Np(¹²C,5n)²⁴⁴Es reaction at 81 MeV (on target) with a production cross section of 0.31±0.12 (micro)b. The mass-yield distribution of the fission fragments is highly asymmetric. The average preneutron-emission total kinetic energy of the fragments was measured to be 186±19 MeV. Based on the ratio of the number of fission events to the measured number of α decays from the electron-capture daughter ²⁴⁴Cf (100% α branch), the probability of delayed fission was determined to be (1.2±0.4) x 10^-4. This value for the delayed fission probability fits the experimentally observed trend of increasing delayed fission probability with increasing Q value for electron-capture

[en] A new nuclear reaction for the production of ²⁴⁰Am was experimentally investigated. Targets of 150-500 μg/cm²²⁴²Pu on 2 μm Ti were produced through molecular deposition. Five irradiations, in which ²⁴²Pu, ^natTi, and ^natNi targets were jointly activated with protons from the Lawrence Berkeley National Laboratory 88-Inch Cyclotron produced ²⁴⁰Am, ⁴⁸V, and ⁵⁷Ni, respectively. The radioactive decay of these nuclides was monitored using high-purity Ge gamma ray detectors in the weeks following irradiation. A maximum ²⁴²Pu(p, 3n)²⁴⁰Am nuclear reaction cross section was measured to be 45 ± 13 mb with 23 MeV protons. While this value is lower than theoretical predictions, it is high enough to be the most viable nuclear reaction for the large-scale production of ²⁴⁰Am. (orig.)

[en] We report on the first independent verification of element 114 at Lawrence Berkeley National Laboratory (LBNL). In the past years the Dubna Gas Filled Recoil Separator (DGFRS) group reported the successful synthesis of superheavy elements (SHE) in numerous ⁴⁸Ca irradiations of actinide targets. Cross sections reported from these experiments are remaining rather constant at the level of a few picobarns, breaking the strong downward trend obvious in hot fusion reactions with other projectiles. Verification of the DGFRS results hence is of paramount importance, but for a long time, confirmation attempts failed to produce SHE in ⁴⁸Ca induced reactions. In a 8-day experiment at the Berkeley Gas-filled Separator (BGS) at LBNL we have observed production of two atoms of element 114 in the reaction ⁴⁸Ca(²⁴²Pu,3-4n)^287,286114. Based on the observed decay properties these decay chains were attributed to the decay of ²⁸⁷114 and ²⁸⁶114 produced in the 3n and 4n channel, respectively. Decay modes, lifetimes, and decay energies are consistent with those reported by the DGFRS group. The 1.4 pb cross sections measured in this work for both the 3n and 4n channels are lower than 3.6 pb and 4.5 pb, respectively, reported by the DGFRS group.

[en] Thulium(III) oxide (Tm₂O₃) targets prepared by the polymer-assisted deposition (PAD) method were irradiated by heavy-ion beams to test the method's feasibility for nuclear science applications. Targets were prepared on silicon nitride backings (thickness of 1000 nm, 344 μg/cm²) and were irradiated with an ⁴⁰Ar beam at a laboratory frame energy of ∼210 MeV (50 particle nA). The root mean squared (RMS) roughness prior to irradiation is 1.1 nm for a ∼250 nm (∼220 μg/cm²) Tm₂O₃ target, and an RMS roughness of 2.0 nm after irradiation was measured by atomic force microscopy (AFM). Scanning electron microscopy of the irradiated target reveals no significant differences in surface homogeneity when compared to imaging prior to irradiation. Target flaking was not observed from monitoring Rutherford scattered particles as a function of time

[en] The polymer-assisted deposition (PAD) method was used to create crack-free homogenous metal oxide films for use as targets in nuclear science applications. Metal oxide films of europium, thulium, and hafnium were prepared as models for actinide oxides. Films produced by a single application of PAD were homogenous and uniform and ranged in thickness from 30 to 320 nm. Reapplication of the PAD method (six times) with a 10% by weight hafnium(IV) solution resulted in an equally homogeneous and uniform film with a total thickness of 600 nm.