Precision mass measurements of neutron-rich nuclei between N=50 and 82

Volume: 420Our knowledge of binding energies of neutron-rich nuclei has experienced a major revision during the last five years due to the introduction of Penning-trap based mass measurements. New mass values for nearly 300 nuclides produced in fission with uncertainties of 10 keV or less have become available. The data produced at three Penning trap facilities at Jyvaskyla, CERN-ISOLDE and Argonne cover all isotopic chains from Ni to Pr, except iodine. In this talk some of this data is reviewed and applied using the mass differentials such as two-neutron binding energy and odd-even staggering to probe their sensitivity on changes in nuclear structure and on the strength of the N=82 shell gap and associated pairing effects.Non peer reviewe

Off-line studies of the laser ionization of yttrium at the IGISOL facility

A laser ion source is under development at the IGISOL facility, Jyvaskyla, in order to address deficiencies in the ion guide technique. The key elements of interest are those of a refractory nature, whose isotopes and isomers are widely studied using both laser spectroscopic and high precision mass measurement techniques. Yttrium has been the first element of choice for the new laser ion source. In this work we present a new coupled dye-Ti:Sapphire laser scheme and give a detailed discussion of the results obtained from laser ionization of yttrium atoms produced in an ion guide via joule heating of a filament. The importance of not only gas purity, but indeed the baseline vacuum pressure in the environment outside the ion guide is discussed in light of the fast gas phase chemistry seen in the yttrium system. A single laser shot model is introduced and is compared to the experimental data in order to extract the level of impurities within the gas cell.Comment: 18 pages submitted to NIM

Isomeric states close to doubly magic 132^{132}Sn studied with JYFLTRAP

The double Penning trap mass spectrometer JYFLTRAP has been employed to measure masses and excitation energies for $11/2^-$ isomers in $^{121}$Cd, $^{123}$Cd, $^{125}$Cd and $^{133}$Te, for $1/2^-$ isomers in $^{129}$In and $^{131}$In, and for $7^-$ isomers in $^{130}$Sn and $^{134}$Sb. These first direct mass measurements of the Cd and In isomers reveal deviations to the excitation energies based on results from beta-decay experiments and yield new information on neutron- and proton-hole states close to $^{132}$Sn. A new excitation energy of 144(4) keV has been determined for $^{123}$Cd$^m$. A good agreement with the precisely known excitation energies of $^{121}$Cd$^m$, $^{130}$Sn$^m$, and $^{134}$Sb$^m$ has been found.Comment: 10 pages, 6 figures, submitted to Phys. Rev.

Q_EC values of the Superallowed beta-Emitters 10-C, 34-Ar, 38-Ca and 46-V

The Q_EC values of the superallowed beta+ emitters 10-C, 34-Ar, 38-Ca and 46-V have been measured with a Penning-trap mass spectrometer to be 3648.12(8), 6061.83(8), 6612.12(7) and 7052.44(10) keV, respectively. All four values are substantially improved in precision over previous results.Comment: 9 pages, 7 figures, 5 table

Production of Zero-Energy Radioactive Nuclear Beams through Extraction from the Liquid-Vapour Interface of Superfluid Helium

A new approach has been investigated to create an ultra-cold radioactive beam from high-energy ions. A 223Ra alpha-decay recoil source has been used to produce radioactive ions in superfluid helium. The alpha spectra demonstrate that the recoiling 219Rn ions have been extracted out of liquid helium. This first observation of the extraction of heavy positive ions across the superfluid helium surface has been possible thanks to the high sensitivity of radioactive ion detection. An efficiency of 36 % has been obtained for the ion extraction out of liquid helium.</p

Mass and low-lying levels of 106,108In from the 106,108Cd(p,nγ) reactions

106In has been studied via the reaction 106Cd(p,nγ)106In in the energy range Ep=7-9 MeV. Inbeam γ-ray excitation functions, γ-γ coincidence measurements, and β+-delayed γ-ray excitation functions have been used to identify thirteen levels in 106In. From this new level scheme the energy separation of the high-spin ground state and the low-spin isomer has been determined to be 28.6±0.5 keV. The threshold energy of the strongest low-lying γ-ray transition yields a mass excess for 106In of -80601±15 keV. Spins for some states are suggested by comparing the excitation functions to Hauser-Feshbach calculations. In-beam γ-ray excitation functions for the 108Cd(p,nγ)108In reaction give a mass excess for the 3+ β+-decaying state in 108In of -84018±12 keV. The systematics of odd-odd In nuclei are discussed in a j-j coupling model

In-trap conversion electron spectroscopy

The Penning trap REXTRAP at ISOLDE was used to test the feasibility of in-trap conversion electron spectroscopy. The results of simulations, experiments with solid conversion electron sources as well as first on-line and tests with trapped radioactive ions are presented. In addition to obtaining high-resolution spectroscopic data, the detection of conversion electrons was found to be a useful tool for the diagnostics of the trap operation. The tests proved the feasibility of in-trap spectroscopy but also revealed some potential problems to be addressed in the future