Selected Publications: Commissioning of the collinear last spectoscopy system in the BECOLA facility at NSCL, K. Minamisono, P.F. Mantica, A. Klose, S. Vinnikova, A. Schneider, B. Johnson, and B.R. Barquest. Nucl Instrum. Methods Phys. Res. A, 709, 85 (2013)
Beta decay of Co-71,73: probing single-particle states approaching doubly-magic Ni-78, M.M. Rajabali, et al., Phys. Rev. C 85, 034326 (2012).
Tests of atomic charge-exchange cells for collinear laser spectroscopy, A. Klose, K. Minamisono, Ch. Geppert, N. Froemmgen, M. Hammen, J. Kraemer, A. Krieger, C.D.P. Levy, P.F. Mantica, W. Noertershaeuser, and S. Vinnikova, Nucl. Instrum. Methods Phys. Res. A 678, 114 (2012).
Beta decay of nuclei around Se-90: search for signatures of a N=56 subshell closure relevant to the r process, M. Quinn, et al., Phys. Rev. C 85, 035807 (2012).
High-spin microsecond isomeric states in Ag-96, A.D. Becerril, et al., Phys. Rev. C 84, 041303(R) (2012).
"Half-lives of ground and isomeric states in Cd-97 and the astrophysical origin of Ru-96,"
G. Lorusso, A. Becerril, A. Amthor, T. Baumann, D. Bazin, J.S. Berryman, B.A. Brown, R.H. Cyburt, H.L. Crawford, A. Estrade, A. Gade, T. Ginter, C.J. Guess, M. Hausmann, G.W. Hitt, P.F. Mantica, M. Matos, R. Meharchand, K. Minamisono, F. Montes, G. Perdikakis, J. Pereira, M. Portillo, H. Schatz, K. Smith, J.B. Stoker, A. Stolz, and R.G.T. Zegers, Phys. Lett. B 699, 141 (2011).
The low-energy properties of atomic nuclei are predicted to show dramatic changes when the ratio of neutrons-to-protons in the nucleus becomes extremely unbalanced. My research group is working to deduce the electromagnetic properties of nuclei that have extreme neutron-to-proton ratios. The desired nuclei, which exist for only fractions of a second, are produced in very small quantities using intermediate-energy reactions at NSCL.
Two electromagnetic properties of primary interest are the nuclear magnetic dipole moment and nuclear electric quadrupole moment. The dipole moment is sensitive to the orbital component of the angular momentum of any unpaired protons and/or neutrons in the nucleus. The dipole moment provides information on the nuclear quantum structure and the occupied single-particle states. The quadrupole moment is a measure of the deviation of the average charge distribution of the nucleus away from spherical symmetry. The shape of the collection of protons and neutrons in the nucleus, e.g. the nuclear collectivity or deformation, can be inferred from the quadrupole moment.
One way to deduce the electromagnetic moments of nuclei is via Collinear Laser Spectroscopy (CLS). The CLS method involves the co-propagation of a low-energy beam (~ 60 keV) of atoms/ions with laser light. Fixed-frequency laser light is Doppler tuned into resonance by varying the energy of the beam, with the subsequent fluorescence detected by a photomultiplier tube. The resulting hyperfine spectrum, a product of the interaction of atomic electrons with the nucleus, is analyzed to extract the nuclear magnetic dipole and electric quadrupole moments.
We have installed and commissioned a CLS beam line in the low-energy beam experimental area at NSCL as part of the Beam Cooling and Laser Spectroscopy (BECOLA) facility. The BECOLA facility also includes a cooler and buncher, which will accept the direct current (DC) rare isotope beams from the NSCL beam thermalization area and convert them into a low-emittance, pulsed beam to improve the sensitivity of the CLS measurement.Stable beams of Ca, K, Fe and Mn have been produced from off-ion sources, and the hyperfine spectra have been collected and analyzed. An example spectrum for stable K-39 is given here, where the four peaks correspond to transitions between hyperfine states that arise from the interaction between the atomic electrons and the K-39 nucleus, which has spin 3/2. The first on-line CLS measurements with short-lived radioisotopes, where sample sizes are of order 10 4 per second, are planned for the coming year.