Paul Mantica
Professor Office: N103 NSCL
Phone: 517-355-9672 456 /
Websites: Research Group - Area
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Nuclear Decay Spectroscopy
(Research Description PDF - 1071 kb)My research has focused on the study of low-energy properties of nuclei far from the valley of ß stability to provide experimental support for the dramatic structure changes predicted for nuclei with extreme neutron-to-proton ratios. Two experimental approaches are used in these studies: ß-NMR spectroscopy to measure ground state moments of nuclei near the proton drip line and ß-decay spectroscopy to probe the low-energy quantum structure of nuclei. Both approaches make use of short-lived, ß-unstable nuclei produced via projectile fragmentation at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University.
Efforts in the ß-decay spectroscopy program have focused on investigating the decay properties of neutron-deficient nuclei towards doubly magic 100Sn. Such studies were not possible at NSCL in the past due to significant quantities of contaminants in our rare isotope beams. Implementation of the new Radio Frequency Fragment Separator (RFFS), funded in part by a Major Research Instrumentation grant from the National Science Foundation, now provides access to a range of nuclei important to studies of both nuclear structure and nuclear astrophysics. One recent study involved characterization of the ß decay of 84Mo, which is a "waiting point" in the astrophysical rapid proton capture (rp-) process pathway. Waiting points are important to the time evolution of the rp-process, since the product nuclide after proton capture (in this case, 85Tc) is unbound, resulting in an equilibrium capture and disintegration scenario that is only broken by the "slow" ß-decay process. We have deduced a more precise and shorter half-life of 84Mo compared to previously reported values, meaning that mass processing along the rp-process in the A~80 region is less hindered than originally thought.
The determination of dipole and quadrupole moments of exotic nuclei can provide insight into new features of nuclear structure. The nuclear magnetic dipole moment is sensitive to the orbital contribution to the nuclear state wave function, while the electric quadrupole moment is a direct measure of the nuclear charge distribution. Nuclear moments at NSCL are measured with the technique of nuclear magnetic resonance on ß-emitting nuclei (ß-NMR). We have recently completed the first ground state quadrupole moment measurement at NSCL. The precise measurement of the quadrupole moment of 37K, produced as a polarized beam using our novel nucleon pickup method, was successful due a recent upgrade of our ß-NMR system that leads to higher oscillating magnetic fields at the sample position. The large quadrupole moment of 37K (see Figure) can be reconciled with theoretical expectations by considering a stronger polarization of the core protons by the valence neutrons.
One opportunity we plan to exploit is the availability of low-energy beams of radioactive ions at NSCL for nuclear moment measurements. We are developing a new laser polarization beam line to spin polarize, in a controlled way via laser optical pumping, slow-moving (< 60 keV) beams of radioactive atoms and/or ions. The spin-polarized species would be implanted into a catcher foil at the center of our ß-NMR apparatus, and resonance techniques would be used to determine ground state dipole and/or quadrupole moments with high precision. The laser polarization project is in collaboration with Prof. Morrissey (Chemistry/NSCL) and Prof. Bollen (Physics and Astronomy/NSCL) and is scheduled for completion in 2011.
Selected Publications
Nuclear Magnetic Moment of the 57Cu Ground State, K. Minamisono, P.F. Mantica, T.J. Mertzimekis, A.D. Davies, M. Hass, J. Pereira, J.S. Pinter, W.F. Rogers, J.B. Stoker, B.E. Tomlin, and R.R. Weerasiri, Phys. Rev. Lett. 2006, 96, 102501.Nuclear Spin Polarization Following Intermediate-Energy Heavy-ion Reactions, D.E. Groh, J.S. Pinter, P.F. Mantica, T.J. Mertzimekis, A.E. Stuchbery, and D.T. Khoa, Phys. Rev. C 2007, 76, 054608.
Onset of Isomers in 125,126,127,128Cd and Weakened Neutron-neutron Interaction Strength, N. Hoteling, W.B. Walters, B.E. Tomlin, P.F. Mantica, J. Pereira, A. Becerril, T. Fleckenstein, A.A. Hecht, G. Lorusso, M. Quinn, J.S. Pinter, and J.B. Stoker, Phys. Rev. C 2007, 76, 044324.
Beta Decay of Neutron-rich 53-56Ca, P.F. Mantica, R. Broda, H.L. Crawford, A. Damaske, B. Fornal, A.A. Hecht, C. Hoffman, M. Horoi, N. Hoteling, R.V.F. Janssens, J. Pereira, J.S. Pinter, J.B. Stoker, S.L. Tabor, T. Sumikama, W.B. Walters, X. Wang, and S. Zhu, Phys. Rev. C 2008, 77, 014313.
Quadrupole Moment of 37K, K. Minamisono, P.F. Mantica, H.L. Crawford, J.S. Pinter, J.B. Stoker, Y. Utsuno, and R.R. Weerasiri, Phys. Lett. B 2008, 662, 389.
