arXiv subjects

M. Dombsky

Publications and source records attributed to M. Dombsky.

5 recordsLinked to original sources

arXiv2013

The interaction of 11Li with 208Pb

Background: 11Li is one of the most studied halo nuclei. The fusion of 11Li with 208Pb has been the subject of a number of theoretical studies with widely differing predictions, ranging over four orders of magnitude, for the fusion excitation function. Purpose: To measure the excitation function for the 11Li + 208Pb reaction. Methods: A stacked foil/degrader assembly of 208Pb targets was irradiated with a 11Li beam producing center of target beam energies from above barrier to near barrier energies (40 to 29 MeV). The intensity of the 11Li beam (chopped) was 1250 p/s and the beam on-target time was 34 hours. The alpha-decay of the stopped evaporation residues was detected in a alpha-detector array at each beam energy in the beam-off period (the beam was on for <= 5 ns and then off for 170 ns). Results: The 215At evaporation residues were associated with the fusion of 11Li with 208Pb. The 213,214At evaporation residues were formed by the breakup of 11Li into 9Li + 2n, with the 9Li fusing with 208Pb. The 214At evaporation residue appears to result from a "quasi-breakup" process. Conclusions: Most of 11Li + 208Pb interactions lead to breakup with a small fraction (<= 11%) leading to complete fusion.

nucl-ex↗

arXiv2010

Isotope Shift Measurements of Stable and Short-Lived Lithium Isotopes for Nuclear Charge Radii Determination

Changes in the mean-square nuclear charge radii along the lithium isotopic chain were determined using a combination of precise isotope shift measurements and theoretical atomic structure calculations. Nuclear charge radii of light elements are of high interest due to the appearance of the nuclear halo phenomenon in this region of the nuclear chart. During the past years we have developed a new laser spectroscopic approach to determine the charge radii of lithium isotopes which combines high sensitivity, speed, and accuracy to measure the extremely small field shift of an 8 ms lifetime isotope with production rates on the order of only 10,000 atoms/s. The method was applied to all bound isotopes of lithium including the two-neutron halo isotope Li-11 at the on-line isotope separators at GSI, Darmstadt, Germany and at TRIUMF, Vancouver, Canada. We describe the laser spectroscopic method in detail, present updated and improved values from theory and experiment, and discuss the results.

physics.atom-ph↗

arXiv2009

Tensor interaction constraints from beta decay recoil spin asymmetry of trapped atoms

We have measured the angular distribution of recoiling daughter nuclei emitted from the Gamow-Teller $β$ decay of spin-polarized $^{80}$Rb. The asymmetry of this distribution vanishes to lowest order in the Standard Model (SM) in pure Gamow-Teller decays, producing an observable very sensitive to new interactions. We measure the non-SM contribution to the asymmetry to be $A_{T}$= 0.015 $\pm$ 0.029 (stat) $\pm$ 0.019 (syst), consistent with the SM prediction. We constrain higher-order SM corrections using the measured momentum dependence of the asymmetry, and their remaining uncertainty dominates the systematic error. Future progress in determining the weak magnetism term theoretically or experimentally would reduce the final errors. We describe the resulting constraints on fundamental 4-Fermi tensor interactions.

nucl-ex↗

arXiv2005

Nuclear Charge Radius of Li-9, Li-11: Halo Neutron: the influence of Halo Neutrons

The nuclear charge radius of Li-11 has been determined for the first time by high precision laser spectroscopy. On-line measurements at TRIUMF-ISAC yielded a Li-7 - Li-11 isotope shift (IS) of 25101.23(13) MHz for the Doppler-free 2s - 3s transition. IS precision for all other bound Li isotopes was also improved. Differences from calculated mass-based IS yield values for change in charge radius along the isotope chain. The charge radius decreases monotonically from Li-6 to Li-9, and then increases from 2.217(35) fm to 2.467(37) fm for Li-11. This is compared to various models, and it is found that a combination of halo neutron correlation and intrinsic core excitation best reproduces the experimental results.

physics.atom-ph↗

arXiv2005

Scalar interaction limits from the beta-neutrino correlation of trapped radioactive atoms

We have set limits on contributions of scalar interactions to nuclear beta decay. A magneto-optical trap (MOT) provides a localized source of atoms suspended in space, so the low-energy recoiling nuclei can freely escape and be detected in coincidence with the beta. This allows reconstruction of the neutrino momentum, and the measurement of the beta-neutrino correlation, in a more direct fashion than previously possible. The beta-neutrino correlation parameter of the 0+ to 0+ pure Fermi decay of 38mK is $\tilde{a}$=0.9981+-0.0030+-0.0037, consistent with the standard model prediction a=1.

nucl-ex↗