Complete structure determination of the astrophysically important nucleus Na below the proton threshold

The fusion–evaporation reaction ¹⁰B(¹²C, 2n) was used to make the first observation of in-beam γ decays from the astrophysically important nucleus ²⁰Na, lying adjacent to the proton drip-line. All states below the proton threshold in ²⁰Na were populated and identified in the experiment. These include new levels, previously unresolved levels, and states located with improved energy precision. The level structure of ²⁰Na, and its γ transitions, are compared to the mirror partner ²⁰F measured simultaneously in this experiment. In particular, a high degree of energy stability is found for all negative parity states. These results are discussed in the context of the nuclear shell model.     

"Safe" Coulomb excitation of 30Mg

We report on the first radioactive beam experiment performed at the recently commissioned REX-ISOLDE facility at CERN in conjunction with the highly efficient gamma spectrometer MINIBALL. Using 30Mg ions accelerated to an energy of 2.25 MeV/u together with a thin (nat)Ni target, Coulomb excitation of the first excited 2+ states of the projectile and target nuclei well below the Coulomb barrier was observed. From the measured relative deexcitation gamma-ray yields the B(E2;0(+)gs-->2(+)1) value of 30Mg was determined to be 241(31)e2 fm4. Our result is lower than values obtained at projectile fragmentation facilities using the intermediate-energy Coulomb excitation method, and confirms the theoretical conjecture that the neutron-rich magnesium isotope 30Mg resides outside the "island of inversion."     

Level structure of 22Mg: implications for the 21Na(p,gamma)22Mg astrophysical reaction rate and for the 22Mg Mass

The level structure of (22)Mg has been studied with high-sensitivity gamma-ray spectroscopy techniques. A complete level scheme is derived incorporating all subthreshold states and all levels in the energy region relevant for novae burning. The excitation energy of the most important astrophysical resonance is measured with improved accuracy and found to differ from previous values. Combining the present result with a recent resonance energy measurement of this state leads to a derived (22)Mg mass excess of -400.5(13) keV.     

A first experimental approach to the 15O + α elastic scattering

The ¹⁵O(α,α)¹⁵O elastic scattering is investigated using a ¹⁵O radioactive beam and a He gas cell limited by Mylar windows. The width of a ¹⁹Ne state at an excitation energy of 5.35MeV is measured as Γ_α = 3.2±1.6keV, in agreement with charge symmetry estimate.     

Isoguanine and 5‐Methyl‐Isocytosine Bases,In Vitro and In Vivo

The synthesis, base‐pairing properties and in vitro and in vivo characteristics of 5‐methyl‐isocytosine (isoC^Me) and isoguanine (isoG) nucleosides, incorporated in an HNA(h) (hexitol nucleic acid)–DNA(d) mosaic backbone, are described. The required h‐isoG phosphoramidite was prepared by a selective deamination as a key step. As demonstrated by T_m measurements the hexitol sugar showed slightly better mismatch discrimination against dT. The d‐isoG base mispairing follows the order T>G>C while the h‐isoG base mispairing follows the order G>C>T. The h‐ and d‐isoC^Me bases mainly mispair with G. Enzymatic incorporation experiments show that the hexitol backbone has a variable effect on selectivity. In the enzymatic assays, isoG misincorporates mainly with T, and isoC^Me misincorporates mainly with A. Further analysis in vivo confirmed the patterns of base‐pair interpretation for the deoxyribose and hexitol isoC^Me/isoG bases in a cellular context, through incorporation of the bases into plasmidic DNA. Results in vivo demonstrated that mispairing and misincorporation was dependent on the backbone scaffold of the base, which indicates rational advances towards orthogonality.     

The contribution of 2N photon absorption in C(γ,2N) reactions for Eγ = 150–400 MeV

The ¹²C(γ,pn) and ¹²C(γ,pp) reactions have been studied using tagged photons of energy E_γ = 150–400 MeV. Recoil momentum distributions are compared to the results of Monte Carlo calculations based on a two-nucleon photon absorption model and two different phase space models. The ¹²C(γ,pn) data at low missing energy are consistent with absorption on 1p² and 1s1p nucleon pairs.     

Development of an automatic multiple dynamic hollow fibre liquid-phase microextraction procedure for specific migration analysis of new active food packagings containing essential oils

A two-phase based hollow fibre liquid-phase microextraction (HFLPME) with a high automatization degree and able to process up to six samples simultaneously by means of a multiple channel syringe pump has been successfully developed. The experimental set-up allows to carry out dynamic extractions with a considerable reduction of sample handling. The system has been applied for the first time to the determination in aqueous food simulant of migrants from prototypes of active packagings to assess their safety before marketing, showing detection limits in the ng g(-1) range, relative standard deviations below 13% and concentration factors ranging from 83 to 338.     

The REX-ISOLDE project

The Radioactive Beam Experiment REX-ISOLDE [1–3] is a pilot experiment at ISOLDE (CERN) testing the new concept of post acceleration of radioactive ion beams by using charge breeding of the ions in a high charge state ion source and the efficient acceleration of the highly charged ions in a short LINAC using modern ion accelerator structures. In order to prepare the ions for the experiments singly charged radioactive ions from the on-line mass separator ISOLDE will be cooled and bunched in a Penning trap, charge bred in an electron beam ion source (EBIS) and finally accelerated in the LINAC. The LINAC consists of a radiofrequency quadrupole (RFQ) accelerator, which accelerates the ions up to 0.3 MeV/u, an interdigital H-type (IH) structure with a final energy between 1.1 and 1.2 MeV/u and three seven gap resonators, which allow the variation of the final energy. With an energy of the radioactive beams between 0.8 MeV/u and 2.2 MeV/u a wide range of experiments in the field of nuclear spectroscopy, astrophysics and solid state physics will be addressed by REX-ISOLDE. This revised version was published online in July 2006 with corrections to the Cover Date.     

The α -decay properties of 186Bi

The α decay of ¹⁸⁶Bi was investigated via the ⁹⁷Mo(⁹²Mo, p2n) reaction and the use of a fragment mass analyzer with a double-sided Si strip detector. In contrast to an earlier work wherein only one α transition was reported, we observed two transitions arising from two isomers in ¹⁸⁶Bi with energies and half-lives of: 7158(20) keV, T_1/2 = 15.0(17) ms; and 7261(20) keV, T_1/2 = 9.8(13) ms.