High-precision Penning Trap Mass Measurements Research Articles

Precision mass measurement of lightweight self-conjugate nucleus 80Zr

Protons and neutrons in the atomic nucleus move in shells analogous to the electronic shell structures of atoms. The nuclear shell structure varies as a result of changes in the nuclear mean field with the number of neutrons N and protons Z, and these variations can be probed by measuring the mass differences between nuclei. The N = Z = 40 self-conjugate nucleus 80Zr is of particular interest, as its proton and neutron shell structures are expected to be very similar, and its ground state is highly deformed. Here we provide evidence for the existence of a deformed double-shell closure in 80Zr through high-precision Penning trap mass measurements of 80–83Zr. Our mass values show that 80Zr is substantially lighter, and thus more strongly bound than predicted. This can be attributed to the deformed shell closure at N = Z = 40 and the large Wigner energy. A statistical Bayesian-model mixing analysis employing several global nuclear mass models demonstrates difficulties with reproducing the observed mass anomaly using current theory. High-precision mass measurements of exotic zirconium nuclei are reported, and reveal a double-shell closure for the deformed nucleus 80Zr, which is more strongly bound than previously thought.

High-precision Penning trap mass measurements of ‘difficult’ elements produced via projectile fragmentation with LEBIT

Rare isotope beams of many elements can be difficult or impossible to obtain at ISOL facilities due to their high melting points or chemical reactivity, but they are easily produced by projectile fragmentation and in-flight separation, a technique that rapidly produces fragments lighter than the projectile in a chemistry-free manner. Until recently, such high-energy projectile fragments could not be reduced to the thermal energies necessary for precision mass measurements in Penning traps. The Low Energy Beam and Ion Trap (LEBIT) facility at the National Superconducting Cyclotron Laboratory (NSCL) has demonstrated that projectile fragment beams can be thermalized and measured in a high-precision Penning trap. Since 2005, over 30 isotopes have been measured with LEBIT, including several isotopes of elements which are difficult for ISOL facilities to produce, such as Fe, Co, Si, Br, and S. These measurements have contributed to our understanding of nuclear structure, nuclear astrophysics, and fundamental symmetries. Some recent highlights include the discovery of an isomeric state in 65Fe, testing the Isobaric Mass Multiplet Equation (IMME) with the A = 32, T = 2 quintet with a measurement of 32Si, probing out to the proton dripline with 70mBr, and studying the N = 28 shell closure with measurements of 40 − 44S. Results of these measurements will be discussed, along with the technical developments which made them possible.

Recent high-precision Penning trap mass measurements performed at LEBIT

Collected here are all publications related to high-precision Penning trap mass measurements performed at LEBIT which were published from 2007 to 2009.

Precision Penning trap mass measurements on exotic ions: status and perspectives

Penning traps are powerful instruments for the precise and accurate mass determination of rare isotopes. At present, many Penning trap facilities installed at radioactive beam facilities provide key data for nuclear astrophysics, for the study of nuclear structure evolution far from stability, and the test of fundamental interactions. This article summarizes the present status and current limits in the field of high-precision Penning trap mass measurements on short-lived exotic ions.

High-precision Penning trap mass measurements of 9,10Be and the one-neutron halo nuclide 11Be

Penning trap mass measurements of 9Be, 10Be (t1/2=1.51 My), and the one-neutron halo nuclide 11Be (t1/2=13.8 s) have been performed using TITAN at TRIUMF. The resulting 11Be mass excess (ME=20177.60(58) keV) is in agreement with the current Atomic Mass Evaluation (AME03) [G. Audi, et al., Nucl. Phys. A 729 (2003) 337] value, but is over an order of magnitude more precise. The precision of the mass values of 9,10Be have been improved by about a factor of four and reveal a ≈2σ deviation from the AME mass values. Results of new atomic physics calculations are presented for the isotope shift of 11Be relative to 9Be, and it is shown that the new mass values essentially remove atomic mass uncertainties as a contributing factor in determining the relative nuclear charge radius from the isotope shift. The new mass values of 10,11Be also allow for a more precise determination of the single-neutron binding energy of the halo neutron in 11Be.