Angular momentum dissipation in16O +58Ni collisions investigated by observation of light particles and? rays

Abstract

A systematic study of angular momentum dissipation in deep-inelastic heavy ion collisions is carried out by combining two experimental methods: the angular correlation of e particles and protons in coincidence with deeply inelastic light fragments; and the first two moments of the y-ray multiplicity. The unified analysis of these data, using a quantum mechanical treatment of the particle anisotropies and statistical decay calculations, yields most probable fragment spins 10=10.8_+l.lh and 13.4_+1.1h for 5SNi and 62Zn, respectively, close to the sticking limit. For the width of the vector spin distribution assumed in our analysis to be equal in all three directions we obtain a= 3.9• 1.3h and 2.9_+ 1.8h for 58Ni and 62Zn, respectively. These values correspond to most probable alignment parameters (P=)=0.66• and 0.82_+0.17 for 58Ni and 62Zn, respectively. As only very few partial waves of this light system undergo deep-inelastic scattering, a directly relates to spin fluctuations, and is compared to asymptotic values from transport theories.

Discrete ?-rays in the reactions of 143 MeV32S with58Ni

“…28. The obtained values for TLF compare well with published data on the reaction ~60 + 5SNi studied through discrete y-rays [4] and alpha particles sequential emission [5]. In the present experiment PLF and TLF alignment may be compared directly: within experimental uncertainties no difference is evi- denced in the Pzz Q-integrated values for complementary fragments, while in a classical approach a smaller alignment is expected for the light fragment, which carries the minor part of transferred angular momentum.…”

“…A reasonable PLF excitation probability was expected in this reaction because of the moderate mass asymmetry. Furthermore, as data on the TLF spin alignment [4,5] and PLF y-emission [6] are available for the 160+ssNi reaction, a comparison between 32S and 160 induced reactions may be interesting. The relevant dynamical parameters of the studied reaction are reported in Table 1.…”

Angular momentum transfer in the deepinelastic reaction 245 MeV32S +64Ni from neutron angular correlations

“…This result is consistent with ~-particle correlation studies [6,7] and with a previous study [32] of deepinelastic collisions in the heavier system 8.5 MeV/u 56Fe+ 165Ho which inferred considerable alignment from the 0o/90 ~ out-of-plane anisotropy of neutrons evaporated from the heavy fragment. Utilizing the same procedure, however, an investigation of the reaction 7 MeV/u 86Kr + 166Er [33] failed to find significant out-of-plane asymmetry.…”

“…The values of the fragment spins exhibited in Fig. 6 are listed in Table 4 in comparison with the classical sticking values calculated for l~ = 72 h. sumption of a Gaussian spin distribution peaked at J~ = Jy = 0 and J~ = Jo Ho et al [7] arrived at the expression…”

“…This procedure was introduced by Wurm et al [6,7] in the analysis of their alpha and proton correlation data. Combining (2) …”