Selected Publications: Evidence for a Change in the Nuclear Mass Surface with the Discovery of the Most Neutron-rich Nuclei with 17 ≤ Z ≤ 25, O.B. Tarasov, et al., Phys. Rev. Lett. 2009, 102, 142501.
Penning Trap Mass Spectroscopy of Neutron-rich Fe and Co Isotopes Around N=40 with LEBIT, R. Ferrer, et al., Phys. Rev. C 2010, 81, 044318.
Discovery of a Nuclear Isomer in 65Fe with Penning Trap Mass Spectrometry, M. Block, et al., Phys. Rev. Lett. 2008, 100, 132501.
States in 23O via Beta Decay of 23N, C. Sumithrarachchi, D.J. Morrissey, et al., Phys. Rev. C 2010, 81, 014302.
Discovery of Exotic Isotopes 40Mg and 42Al Suggests Neutron Drip Line Slant Toward Heavier Nuclei, T. Baumann, et al., Nature 2007, 449, 1022.
The rp Process and Masses of N ≈ Z ≈ 34 Nuclides, J. Savory, et al., Phys. Rev. Lett. 2009, 102, 132501.
Modern Nuclear Chemistry, W. Loveland, D.J. Morrissey and G.T. Seaborg (Wiley Interscience,2006).
Radioactive Nuclear Beam Facilities Based on Projectile Fragmentation, D. J. Morrissey, and B. M. Sherrill, Proc. Royal Soc. A, 356. 1985 (1998), and Lecture Notes on Physics 2004, 651, 113.
We carry out research in nuclear chemistry that is centered on the production and use of the most exotic, short-lived nuclei. We have applied this knowledge to produce beams of very exotic radioactive ions. These nuclei are interesting in their own right, some of which have not been observed before. My graduate students have worked on unraveling the mechanisms of nuclear reactions and on studying the decay properties of the most exotic nuclei. The NSCL is a unique facility that brings together a strong group of nuclear scientists and provides an exceptional setting for studying the properties of nuclei. The cyclotrons accelerate ions that span the periodic table and have very high kinetic energies. When the fast ions react with a target nucleus, the incident ion is often broken into nuclear fragments with a distribution of sizes, some of which are very unstable and quite unusual. The probability distributions of the products were early subjects of study by my group and can be predicted with reasonable accuracy. The momenta, or velocities, of the fragments were shown to be distributed around that of the beam and to be predicted by models of the nuclear reaction. These fast moving fragments can be passed through an isotope separator to produce beams of individual radioactive ions. We worked on developing these fragment separators and they have become the central instruments for research at NSCL and have provided intense beams of unstable ions to study nuclear reactions and decay properties. The NSCL currently relies on the second generation fragment separator completed in 2001 and a revolutionary fragment separator is being designed for the FRIB facility that will replace the NSCL.
The distribution of fragments from the reaction of 76Ge with 9Be as a function of atomic number, Z, and neutron excess, N-Z. Each dot represents a nucleus that was individually identified in the experiment and particles to the right of the red line were produced and identified for the first time ever.
Along with using the new fragment separator, our group has completed the construction and development of an auxiliary device to deliver the exotic reaction products at thermal energies. In this project, we have extended the ion-guide ion-source (IGISOL) technique developed primarily in Europe and Japan and recently by another group at Argonne National Lab to collect individual ions. The new device is tailored to stop and collect the exotic isotopes produced by the A1900 fragment separator at NSCL using a differentially pumped gas cell in a process related to atmospheric sampling mass spectrometry. The so-called gas-catcher system has begun operation and many successful and extremely precise mass measurements have been carried out at the NSCL by the group headed by Prof. Bollen. We are currently developing the next-generation devices for thermalization of projectile fragments that will be able to provide the large variety of fragments needed for the FRIB facility.