Cross-section limits for the 208 Pb(86 Kr,n)293118 reaction

In April-May, 2001, the previously reported experiment to synthesize element 118 using the ²⁰⁸Pb(⁸⁶Kr,n)²⁹³118 reaction was repeated. No events corresponding to the synthesis of element 118 were observed with a total beam dose of 2.6 x 10¹⁸ ions. The simple upper-limit cross-sections (1 event) were 0.9 and 0.6 pb for evaporation residue magnetic rigidities of 2.00 Tm and 2.12 Tm, respectively. A more detailed cross-section calculation, accounting for an assumed narrow excitation function, the energy loss of the beam in traversing the target and the uncertainty in the magnetic rigidity of the Z = 118 recoils is also presented. Re-analysis of the primary data files from the 1999 experiment showed the reported element 118 events are not in the original data. The current results put constraints on the production cross-section for synthesis of very heavy nuclei in cold-fusion reactions.Received: 2 September 2002, Revised: 10 April 2003, Published online: 18 November 2003PACS: 25.70.Gh Compound nucleus - 25.70.Jj Fusion and fusion-fission reactions - 27.90. + b      

Wild double tangent ball embeddings of spheres in En

It has been known for years that a 2-sphere Σ in E³ must be flatly embedded if it has double tangent balls on opposite sides of Σ at each of its points. However, when the double tangent balls are not required to be on opposite sides of Σ, pathological embeddings exist. This paper details the allowable wild embeddings of spheres having these indiscrete double tangent balls and discusses the higher dimensional analogues.     

Further studies of large collision residues in relativistic heavy-ion reactions with heavy nuclei

Target residue mass and charge distributions have been measured radiochemically for the reaction of 25.2 GeV ¹²C ions with Au and Pb. Enhanced product yields for A = 140?170 are found that are not present in reactions of Pb with GeV protons. The shape of the mass distribution in this region is used to define a pre-equilibrium product mass distribution.     

Reflection asymmetry of the fission transition nucleus 235U

An analysis of the energy variation of the fission cross section and fragment angular distributions for the ²³⁴U (n,f) reaction reveals that the nuclear is reflection assymetric at the inner barrier.     

Implications of the target residue mass and charge distributions in the interaction of 8.0 GeV20Ne with181Ta

Target residue mass and charge distributions have been measured radioanalytically for the reaction of 8.0 GeV²⁰Ne ions with Ta. These distributions are very similar to those distributions observed in the reaction of Ta with protons of equivalent total energy rather than equivalent velocity. Detailed comparisons of the production cross sections for near target residues with abrasion-ablation model calculations show these products to have an excitation energy of ～75 MeV.     

Application of matrix solid-phase dispersion in the determination of dibenzo[a,l]pyrene content of experimental animal diets used in a large-scale tumor study.

A method utilizing matrix solid-phase dispersion (MSPD) was developed for isolation and determination of dibenzo[a,l]pyrene (DBP) in experimental rainbow-trout diets used in a large-scale carcinogenesis study. A 0.5 g sample of moist ration containing 0-225 ppm DBP (dry basis) was mixed with 2 g C18 sorbent and benzo[a]pyrene internal standard was added to the mixture. Extraction and clean-up were accomplished in a single step by extracting the sample mixture with hexane-benzene 4:1 from a cartridge containing 2 g Florisil. DBP was quantified by HPLC on a C5 bonded phase column with fluorescence detection. Mean analytical recovery of DBP from control diet spiked at three concentration levels was 101 to 107% with relative standard deviations of 1 to 7%. The limit of detection of DBP was equivalent to 0.014 ppm in the ration. Application of the method to verification of DBP levels in trout rations from the carcinogenesis study is described. Control ration (0 ppm DBP) was screened for possible DBP contamination and none was found. This is the first report on analysis of DBP in experimental animal diets.     

Dechaos — A program for automatic or interactive analysis of gamma-ray spectra

DECHAOS is a gamma-ray spectral analysis program for personal computers. The program offers two modes of operation, automatic or interactive. The spectra to be analyzed can be acquired using any pulse height analyzer. The program includes routines for energy calibration, peak shape and efficiency calibration. Complex multiplets can be resolved automatically with the peak areas being determined using least-squares fitting techniques. Output tables include all data used in the calculation and peak information. The program is public domain software.     

New superheavy element isotopes: ²⁴²Pu(⁴⁸Ca,5n) ²⁸⁵114

The new, neutron-deficient, superheavy element isotope 2??114 was produced in ??Ca irradiations of 2?2Pu targets at a center-of-target beam energy of 256 MeV (E*=50 MeV). The α decay of 2??114was followed by the sequential α decay of four daughter nuclides, 281Cn, 277Ds, 273Hs, and 269Sg. 265Rf was observed to decay by spontaneous fission. The measured α-decay Q values were compared with those from a macroscopic-microscopic nuclear mass model to give insight into superheavy element shell effects. The2?2Pu (??Ca,5n2)2??114 cross section was 0.6(-0.5)+0.9 pb.