What are nuclei really like? This is the primary question of nuclear science--a blend of chemistry and physics, with a dash of computer science (for data acquisition and analysis) and nuclear engineering (for neutron facilities). Partial answers to the question come from small scale experiments; the simple ones (based on one discipline or technique) have been done, but interesting questions remain to be answered by a suitable blend of techniques. We emphasize the studies of radioactive materials that require chemical isolation and purification combined with high precision measurements of radiations accompanying radioactive decay.
Some projects are chosen because of their obvious applications (e.g., analyzing nuclear waste, or contributing to a catalog of gamma-ray spectra) and others are chosen "just for fun" (e.g., characterizing the decay of 234Th and the Pa isomers it produces). Most of our laboratory work is carried out in the Neutron Science Laboratory on the Ann Arbor North Campus. Here we produce radioactive materials by "fast” neutron irradiations, develop chemical separations, and study the gamma rays emitted in radioactive decay.
The components of a mixture of radioactive materials are most likely to be identified by gamma-ray spectroscopy, but the relation between number of decays and number of gamma rays is generally not precisely known (typical uncertainties are 3-10%). We are developing techniques to allow measuring this property much more precisely (0.1-0.6% uncertainties). A key part of the technique is knowing the purity of our samples from analysis of the fractions, pure and impure, obtained during a purification process. Often the mass of each important component (aside from solvent) may be less than a nanogram. The technique has been applied to several readily available nuclides that can serve as calibration standards in other laboratories.
In some cases we collaborate with groups from other institutions, e.g., use magnetic lens to separate products of beams of heavy ions from accelerators at Michigan State University and Notre Dame. These collaborations provide physical means of isolation and identification of radioactive materials when chemical techniques are not feasible.
"Nuclear Reactions with Radioactive, Isomer Beams: Coulomb Excitation of 18F.g.s. and its JII = 5+ Isomer 18Fm using a Large Position-sensitive NaI array", J.A. Zimmerman, F.D. Becchetti, H.C. Griffin, D.A. Roberts, M.Y. Lee, T.W. O'Donnell, J.A. Brown, R.M. Ronningen, T. Glasmacher, R.W. Ibbotson, H. Scheit, B. Pritychenko, D.W. Anthony, P.A. Lofy, M. Steiner, Nucl. Instr. Methods A 579 (2007) 476-480.
"X- and ?-ray emissions observed in the decay of 237Np and 233Pa", Daniel J. DeVries, Henry C. Griffin, Appl. Radiat. Isotopes 66 (2008) 668.
"Photon emissions observed in the decay of 233Th", Daniel J. DeVries and Henry C. Griffin, Appl. Radiat. Isotopes 66 (2008) 1999.
"Quantitative gamma-ray spectroscopy of 237-239Np", Henry C. Griffin, Krishnaswamy Rengan, J. Radioanal. Nucl. Chem. 276 (2008) 731-736.
"Absolute Intensities of ? Rays Emitted in the Decay of 239U", Henry C. Griffin, in Fission and Properties of Neutron-Rich Nuclei, J.H. Hamilton, A.V. Ramayya, H.K. Carter, eds., World Scientific (2008) 264-9.
"New Experimental Approach for Heavy and Superheavy Element Production", M. Barbui, T. Materna, P. Sahu, A. Wieloch, F.D. Becchetti, G. Dhubaryan, M. Cinausero, T. W. O'Donnell, D. Fabris, H. Griffin, K. Hagel, S. Kowalski, M. Lunardon, Z. Majka, S. Moretto, R. Murthy, J.B. Natowitz, G. Nebbia, S. Pesente, G. Piete, L. Qin, V. Rizzi, Z. Sosin, G. Souliotis, G. Viesti, R. Wada, J. Wang; International J. of Modern Physics E-Nuclear Physics 18 (2009) 1036-1043.