R. J. Charity

Democratic Decay ofBe6Exposed by Correlations

The interaction of an E/A=70-MeV (7)Be beam with a Be target was used to populate levels in (6)Be following neutron knockout reactions. The three-body decay of the ground and first excited states into the α+p+p exit channel were detected in the High Resolution Array. Precise three-body correlations extracted from the experimental data allowed us to obtain insight into the mechanism of the three-body democratic decay. The correlation data are in good agreement with a three-cluster-model calculation and thus validate this theoretical approach over a broad energy range.

Correlations between reaction product yields as a tool for probing heavy-ion reaction scenarios

Experimental multidimensional joint distributions of neutrons and charged reaction products were analyzed for 136 Xe + 209 Bi reactions at E/A = 28, 40, and 62 MeV and were found to exhibit several different types of prominent correlation patterns. Some of these correlations have a simple explanation in terms of the system excitation energy and pose little challenge to most statistical decay theories. However, several other types of correlation patterns are difficult to reconcile with some, but not other, possible reaction scenarios. In this respect, correlations between the average atomic numbers of intermediate-mass fragments, on the one hand, and light particle multiplicities, on the other, are notable. This kind of multiparticle correlation provides a useful tool for probing reaction scenarios, which is different from the traditional approach of interpreting inclusive yields of individual reaction products.

2p-2p decay of {sup 8}C and isospin-allowed 2p decay of the isobaric-analog state in {sup 8}B

8 C is found to decay to four protons and an α particle in two 2p emission steps. The correlations between the protons in the first step ( 8 C to 6 Be) exhibit a significant enhancement in the region of the decay phase space where the two protons have small relative energy, a region sometimes called the diproton region. The decay of the isobaric analog of 8 C in 8 B is also found to decay by 2p emission. This is the first case of isospin-allowed 2p decay between isobaric analog states.

Comprehensive {gamma}-ray spectroscopy of rotational bands in the N=Z+1 nucleus {sup 61}Zn

The Zn-61(30)31 nucleus has been studied via the combined data of two fusion-evaporation reaction experiments using a Ar-36 beam and a Si-28 target foil. The experimental setups involved the Ge array GAMMASPHERE and neutron and charged particle detectors placed around the target position. The resulting level scheme comprises about 120 excited states connected via some 180 gamma-ray transitions. In total, seven rotational structures were identified up to I similar to 25 or higher and compared with predictions from cranked Nilsson-Strutinsky calculations.

Characterization of superdeformed bands in {sup 62}Zn

Combined data from four fusion-evaporation reaction experiments were utilized to investigate deformed and superdeformed structures in Zn-62(30)32. Combination of the Gammasphere gamma-ray spectrometer and ancillary particle detection systems allowed for the connection of rotational bands to well-known, low-lying excited states in Zn-62, as well as spectroscopy of discrete high-spin states reaching excitation energies of E-x=42.5 MeV. Four well- or superdeformed bands in Zn-62 are characterized and described by means of cranked Nilsson-Strutinsky calculations.

Particle decay of {sup 12}Be excited states

The breakup of E/A=50 MeV (12)Be fragments following inelastic scattering off of hydrogen and carbon target nuclei has been studied. The breakup channels alpha+(8)He, (6)He+(6)He, t+(9)Li, and p+(11)Li were observed. Two doublets at excitation energies of 12.8 and 15.5 MeV were found for the alpha+(8)He channel. A low-energy shoulder in the excitation-energy spectra at 10.2 MeV indicates one or more additional states. This work could not confirm the presence of (6)He-(6)He rotational structure reported by Freer [Phys. Rev. C 63, 034301 (2001)], although possible peaks at excitation energies of 13.5 and 14.5 MeV were found for (6)He+(6)He decay. Significant structure is observed in the excitation-energy spectrum for p+(11)Li at 25-30 MeV which maybe associated with T=3 analog states.

Prompt Proton Decay in the Vicinity of 56Ni

A new decay mode, the so called prompt proton decay, was discovered in 1998. It has since proven to be an important decay mechanism for several neutron deficient nuclei in the A similar to 60 region. To measure with high accuracy the energies and angular distributions of these protons, a state-of-the-art charged particle detector - LuWuSiA - was developed. It was first utilized during a fusion-evaporation reaction experiment performed at Argonne National Laboratory, U.S.A. In this contribution, the characteristics of the prompt proton decay are discussed along with the special features of LuWuSiA as well as a revisit to the prompt proton decay in Cu-58.

Rotational bands near 56Ni

Rotational bands have been found in Co-57 and Ni-57, using Gammasphere in conjunction with the Microball and 30 neutron detectors. The bands in Co-57, extending the mass 60 region of deformation down to Z = 27, are signature partner sequences. The quadrupole moments and dynamic moments of inertia of the new bands in both nuclei are similar to those of rotational sequences in the neighboring nuclei. The high-spin structure of Co-57 is compared with Skyrme Hartree-Fock calculations.

Collisions between 48Ti + 93Nb at 917 MeV.

Collisions between {sup 48}Ti + {sup 93}Nb at 19.1 MeV/nucleon were studied using two 4{pi} detection systems. A reconstruction procedure was developed to determine the mass, kinetic, and excitation energies of the primary projectile and targetlike fragments. The results show a broad range of mechanisms. These results were compared with predictions of the quantum-molecular dynamics model. {copyright} {ital 1996 The American Physical Society.}

Energy Dependence of Multifragmentation in 84Kr+197Au Reactions

The relationship between observed intermediate mass fragment and total charged particle multiplicities has been measured for [sup 84]Kr + [sup 197]Au collisions at energies between [ital E]/[ital A]=35 and 400 MeV. Fragment multiplicities are greatest for central or near-central collisions. For these collisions, fragment production increases up to [ital E]/[ital A][approx]100 MeV, and then decreases at higher energies.