Heavy-ion induced transfer and strongly-damped reactions

The study of light-ion induced few-nucleon transfer reactions has contributed signifiacntly to the understanding of nuclear structure. Single-nucleon transfer is a direct probe of single-particle shell structure while two-nucleon transfer is a direct probe of pairing correlations in nuclei. From 1964-75 our research exploited the Rochester MP Tandem accelerator plus Enge Split-pole magnetic spectrometer for such studies as can be seen from the first 20 publications listed of our transfer reactions studies.

The advent of 4 arrays of Compton-suppressed Ge -ray detectors made it feasible to study heavy-ion induced transfer reactions to investigate intruguing aspects of nuclear structure. This was exploited extensively in the 1980s and 1990s [1]. Examples are selective population of high-j orbitals in actinide nuclei, and inelastic excitation accompanied by pair-transfer allowing study of the spin dependence of pairing correlations in two-nucleon transfer reactions [2]. Diabolic pair transfer [3,4,5], a manifestation of Berry phase [6] in nuclei, involves pair transfer across a band crossing, while enhanced multinucleon-transfer [7,8] between two colliding superfluid nuclei, at subbarrier energies, could lead to the nuclear Josephson effect [9]. Our first search for diabolic pair transfer had insufficient sensitivity [9]. Modern detectors plus neutron-rich radioactive Sn beams may enable study of nuclear Josephson effects and diabolical pair transfer [1].

Heavy-ion induced transfer, and especially strongly-damped reactions provide a powerful means of populating nuclear states in neutron rich nuclei. Both heavy-ion induced transfer reactions and strongly-damped reactions have been used with CHICO plus Gammasphere to populate and explore high-spin states in neutron rich nuclei ranging from A=30 up to the actinide nuclei as listed in the attached publication list. Collaborators from the University of Surrey, University of Massachussetts at Lowell, Argonne National Laboratory and LBNL/UC Berkeley initiated some of our recent studies and such work will remain a cornerstone of the proposed research program with stable beams.

This program has led to 9 Ph.D. theses; S. Juutinen (Jyvaskyla, 1988), X.T. Liu (Knoxville, 1988), W.J. Kernan (Rochester, 1989), M.A. Stoyer (Berkeley, 1990), K.G. Helmer (Rochester, 1992), M. Devlin (Rochester, 1995), A.D. Yamamoto (Surrey, 2004), J.J. Valiente Dobón (Surrey, 2004), and E. Ngijoi-Yogo (Lowell 2004).

The scientific impact of this use of transfer reactions to study nuclear structure can be evaluated from the publication list.

1) C.Y. Wu, W. von Oertzen, D. Cline, M.W. Guidry, Annu. Rev. Nucl. Part. Sci, 40, 285 (1990).

2) C.Y. Wu, X.T. Liu, W.J. Kernan, D. Cline, T. Czosnyka, M.W. Guidry, A.E. Kavka, R.W. Kincaid, B. Kotlinski, S.P. Sorensen, E. Vogt., Phys. Rev. C 39, 298 (1989).

3) R.S. Nikam and P. Ring, Phys. Rev. Lett. 58, 980 (1987).

4) L.F. Canto, P. Ring, Y. Sun, J. O. Rasmussen, S. Y. Chu, and M. A. Stoyer., Phys. Rev. C 47, 2836 (1993).

5) K.G. Helmer, C.Y. Wu, D. Cline, A.E. Kavka, W.J. Kernan, E.G. Vogt, M.W. Guidry, X.L. Han, R.W. Kincaid, X.T. Liu, H. Schecter, J.O. Rasmussen, A. Schihab-Eldin, M.A. Stoyer, and M.L. Halbert, Phys. Rev. C 48, 1879 (1993).

6) M.V. Berry, Proc. R. Soc. London, Ser. A 392, 45 (1984).

7) W.J. Kernan, C.Y. Wu, X.T. Liu, D. Cline, T. Czosnyka, M.W. Guidry, M. Halbert, A.E. Kavka, R.W. Kincaid, S.P. Sorensen, E.G. Vogt., Nucl. Phys. A524, 344 (1991).

8) J.H. Sorensen and A. Winther, Phys. Rev. C 47, 1691 (1993).

9) K. Dietrich, Ann. Phys. 66, 480 (1971).