Precision mass measurements of neutron-rich Y, Nb, Mo, Tc, Ru, Rh, and Pd isotopes

Direct mass measurements with typical uncertainties of 1-10keV have been performed for the first time for ten neutron-rich isotopes ^{102, 103}Y , ¹⁰⁸Nb , ¹¹¹Mo , ^{113, 114}Tc , ¹¹⁶Ru , ¹¹⁹Rh , and ^{121, 122}Pd . The obtained mass data compared with the 2003 atomic-mass evaluation shows systematic overestimation of binding energies far from stability. The relationship between two-neutron separation energies, nuclear structure and shape changes has been investigated by comparing the experimental data with a theoretical calculation based on the Hartree-Fock-Bogoliubov approximation using modern energy density functionals.     

Penning-trap mass measurements on <Superscript>92, 94-98, 100</Superscript>Mo with JYFLTRAP

Penning-trap measurements on stable ^{92, 94-98, 100}Mo isotopes have been performed with relative accuracy of \(\ensuremath 1\cdot 10^{-8}\) with the JYFLTRAP Penning-trap mass spectrometer by using ⁸⁵Rb as a reference. The Mo isotopes have been found to be about 3keV more bound than given in the Atomic Mass Evaluation 2003 (AME03). The results confirm that the discrepancy between the ISOLTRAP and JYFLTRAP data for ^101-105Cd isotopes was due to an erroneous value in the AME03 for ⁹⁶Mo used as a reference at JYFLTRAP. The measured frequency ratios of Mo isotopes have been used to update mass-excess values of 30 neutron-deficient nuclides measured at JYFLTRAP.     

Double-β decay studies with JYFLTRAP

We have applied JYFLTRAP double Penning trap mass spectrometer to study several double-β decay Q values that could be useful for the search of neutrinoless double-β decay and, hence for the determination of neutrino properties.     

The use of the ion guide technique for collinear laser spectroscopy

The present paper introduces the Ion Guide Isotope Separator On-Line IGISOL. In addition, different ion guide types for different reaction types are reviewed. Further, plans to improve IGISOL performance are presented. This revised version was published online in August 2006 with corrections to the Cover Date.     

Production of pure 133mXe for CTBTO

Underground nuclear weapon detonations release gaseous species into the atmosphere. The most interesting isotopes/isomers from the detection point of view are ^131mXe, ^133mXe, ¹³³Xe and ¹³⁵Xe. We have developed a method that employs high-precision Penning trap mass spectrometry at the JYFLTRAP facility, the University of Jyväskylä, to produce pure calibration samples of these isotopes/isomers. Among developments this work required a new mass resolution record of a few parts-per-million. Here the status and future plans of the project are reviewed.     

Q values of the superallowed beta emitters 26Alm, 42Sc, and 46V and their impact on Vud and the unitarity of the Cabibbo-Kobayashi-Maskawa matrix

The beta-decay Q(EC) values of the superallowed beta emitters 26Alm, 42Sc, and 46V have been measured with a Penning trap to a relative precision of better than 8 x 10(-9). Our result for 46V, 7052.72(31) keV, confirms a recent measurement that differed from the previously accepted reaction-based Q(EC) value. However, our results for 26Alm and 42Sc, 4232.83(13) keV and 6426.13(21) keV, are consistent with previous reaction-based values. By eliminating the possibility of a systematic difference between the two techniques, this result demonstrates that no significant shift in the deduced value of Vud should be anticipated.     

Mass measurement on the rp-process waiting point 72Kr

The mass of one of the three major waiting points in the astrophysical rp process 72Kr was measured for the first time with the Penning trap mass spectrometer ISOLTRAP. The measurement yielded a relative mass uncertainty of deltam/m=1.2x10(-7) (deltam=8 keV). (73,74)Kr, also needed for astrophysical calculations, were measured with more than 1 order of magnitude improved accuracy. We use the ISOLTRAP masses of 72-74Kr to reanalyze the role of 72Kr (T(1/2)=17.2 s) in the rp process during x-ray bursts and conclude that 72Kr is a strong waiting point delaying the burst duration with at least 80% of its beta-decay half-life.     

Decay heat studies for nuclear energy

The energy associated with the decay of fission products plays an important role in the estimation of the amount of heat released by nuclear fuel in reactors. In this article we present results of the study of the beta decay of some refractory isotopes that were considered important contributors to the decay heat in reactors. The measurements were performed at the IGISOL facility of the University of Jyväskylä, Finland. In these studies we have combined for the first time a Penning trap (JYFLTRAP), which was used as a high resolution isobaric separator, with a total absorption spectrometer. The results of the measurements as well as their consequences for decay heat summation calculations are discussed.     

First precision mass measurements of refractory fission fragments

Atomic masses of 95-100Sr, 98-105Zr, and [corrected] 102-110Mo and have been measured with a precision of 10 keV employing a Penning trap setup at the IGISOL facility. Masses of 104,105Zr and 109,110Mo are measured for the first time. Our improved results indicate significant deviations from the previously published values deduced from beta end point measurements. The most neutron-rich studied isotopes are found to be significantly less bound (1 MeV) compared to the 2003 atomic mass evaluation. A strong correlation between nuclear deformation and the binding energy is observed in the two-neutron separation energy in all studied isotope chains.     

Reinvestigation of the beta-decay of 110Mo

The beta-decay of the neutron-rich nucleus ¹¹⁰Mo, separated by the IGISOL on-line mass separator from other fission products, has been investigated by using beta-gamma and gamma-gamma coincidence techniques. The decay scheme of ¹¹⁰Mo has been revised, including 3 new excited states and 7 new transitions in ¹¹⁰Tc. The -feedings were measured and values and B(GT) values were deduced based on a -value from systematics. Three excited 1 ⁺ states in ¹¹⁰Tc fed by spin-flip allowed-unhindered beta transitions were identified. The deduced beta-decay strengths are compared with the Gamow-Teller strength distribution obtained from a macroscopic-microscopic calculation. The role of the asymptotic quantum numbers in the context of the allowed beta-decay is discussed.Received: 5 May 2003, Revised: 13 June 2003, Published online: 26 November 2003PACS: 27.60. + j - 21.10.Tg Lifetimes - 23.20.Lv Gamma transitions and level energiesJ.C. Wang: Present address: Argonne National Laboratory, 9700 S. Cass Ave., Room F-133, Bldg 203, Argonne, IL 60439, USA;