Analysis of decay data from neutron-rich nuclei

The β-decays of the neutron-rich nuclei ¹²Be and ²⁹Ne have been studied. The statistical correlations between the almost identical half-lives of ¹²Be and its daughter ¹²B are analysed for a large sample of ¹²Be decay data. Stringent mutual bounds are obtained on the parameter set, leading to a precise determination of the ¹²Be half-life of 21.50±0.04 ms. From a simultaneous detection of β-particles and neutrons from the decay of ²⁹Ne the neutron emission probability, P_n, is determined to 17±5%. No indication of two-neutron emission is seen from this nucleus. An upper limit of 2.2% (90% confidence level) is established for P_2n. Received: 3 May 2001 / Accepted: 6 August 2001     

Gold-Catalyzed [3+2] Carbocycloaddition Reaction of Pinacol Alkenylboronates: Stereospecific Synthesis of Boryl-Functionalized Cyclopentene Derivatives

Gold-catalysis has enabled new synthetic opportunities in the chemistry of vinyldiazo compounds. Herein, we report the gold-catalyzed reaction of stabilized vinyldiazo compounds with pinacol alkenylboronates to provide boryl-functionalized cyclopentene derivatives through a formal [3+2] carbocycloaddition reaction, a very unusual pathway in alkenylboronate chemistry. This reaction proceeds with high regio- and stereoselectivity. The synthetic usefulness of the resulting borylated cyclopentene derivatives toward the synthesis of densely functionalized cyclopentanoids is also demonstrated.     

New perspectives in the studies of resonance scattering

We consider various possibilities for studies of nuclear structure in resonance reactions induced by radioactive beam. We discuss investigations on both sides of nuclear stability as well as studies of the α-cluster structure of light nuclei applying the reverse geometry thick target method.     

Beta-delayed two-proton emission at ISOLDE

The process of β-delayed two-proton emission has attracted much interest over the past two decades, since it was hoped that the study of this process would provide information on correlations inside nuclei. At ISOLDE ³¹Ar has been extensively studied in three experiments during the past decade. We review these studies by comparing the new physics results that have emerged from the different experiments and by highlighting the technical development leading to these results. The β-delayed two-proton emission is, in most cases, simply an extension of β-delayed single proton emission to high lying states that are unstable to proton emission, thus no sign of correlations has been seen. This revised version was published online in July 2006 with corrections to the Cover Date.     

A Study in the Use of Linear Programming for School Planning in Odense

This paper considers the school situation in Odense, Denmark, in 1992. School children, according to a forecast for the various census districts of the city, are assigned to school facilities, existing and planned, by means of linear programming. The resulting solution gives an indication of where in the city there will be an excess or deficit of school capacity. This provides an easy way of evaluating alternative school system expansion plans. Sample results are given, and there is also a discussion of some implementation aspects of this case study.     

New isotope227Rn and revised halflives for223Rn and226Rn

Neutron-rich isotopes of radon, produced by spallation reactions in a ThC² target and selected chemically, were mass-separated and used as samples for radiation counting experiments. Assignments of the activities to radon isotopes were confirmed by genetic relationships to the previously known francium daughters. The halflife for the new isotope²²⁷Rn is 23±1 s and that for²²⁶Rn is 7.4±0.1 min. X-rays,γ-rays, and conversion electrons from the²²³Rn activity were measured. The decay patterns ofK X-rays and known gamma transitions in the²²³Fr daughter yield a halflife of 23.2± 0.4 min for²²³Rn, in contrast to the value of 43± 5 min reported earlier. Energies, intensities, and likely multipolarities for the most prominent gamma transitions in the²²³Rn→²²³Fr decay are presented.     

Nuclear shape transition in neutron-deficient gold isotopes

On-line resonance ionization mass spectrometry has been applied to determine the isotope shift and hyperfine structure of^185–189Au and tne I=11/2 isomer of¹⁸⁹Au in the 6s²S_1/2 6p²P_1/2=268 nm) transition. The Au atoms were obtained as daughters of mass-separated Hg isotopes produced at the ISOLDE facility at CERN, ionized by a three-step resonant photoionization process, detected and mass-selected by time of flight. A drastic change of the nuclear charge radius was observed between¹⁸⁷Au and¹⁸⁶Au, which is interpreted as an onset of strong deformation of ₂ 0.25 in¹⁸⁶Au and¹⁸⁵Au.This work has been supported by the Bundesministerium für Forschung und Technologie. One of us, J. Wood was supported in part by the U.S. Department of Energy, Contract DE-AS05-80 ER 10599.     

Optimisation of flow-injection-hydride generation inductively coupled plasma spectrometric determination of selenium in electrolytic manganese

Flow-injection-hydride generation procedure for Se in electrolytic manganese was optimized by means of the experimental design approach. Instrumental variables like power supplied (P), sample (F) and argon (G) flow rates together with chemical variables like NaBH₄ and HCl concentrations were studied. In case of the chemical variables, it was concluded that sodium tetrahydridoborate concentrations higher than 1.0% extinguished the plasma while HCl concentration should always be higher than 0.6 mol dm⁻³. The analysis of effects suggested that all the instrumental variables are significant factors, and the optimum conditions were P = 1550 W, F = 4.75 mL min⁻¹ and G = 0.6 mL min⁻¹. The influence of Mn was specially studied and it was concluded that the interferences were negligible if Mn is below 2.0 g L⁻¹. In the same sense, the interferences of antimony(III), arsenic(V) and mercury(II) were also considered negligible. Finally, a detection limit of 0.0005% (w/w) was obtained (a repeatability R.S.D. <2.0% for all Se concentrations tried). Some manganese samples were also spiked with different concentrations of Se(IV) and the results demonstrated to be in good statistical agreement with expected values.