Production of fastαparticles inAu20collisions studied by counting the simultaneously emitted neutrons

Influence of projectile cluster properties on fragment emission in incomplete-fusion reactions

“…The investigations [-6 9, 15], however, do not support this conclusion. A considerable number of fragments from both the inelastic breakup [5] and sequential decay [4,9] populates predominantly the low-energy part of the fragment spectrum and this population, which increases with the beam energy, can be a possible explanation of the effect observed by Gelbke et al [13]. The highenergy fragments come mainly from both the directtransfer and the elastic breakup of the projectile but the first process dominates [4,5].…”

“…High-excited heavy projectile-like fragments, formed by the direct transfer as a first step, undergo a sequential decay mainly by alpha-particle emission which is due to its low threshold. Higher beam energies lead not only to the increase of the projectile-breakup contribution [5] but also to the rise of the amount of sequential decay events [4,9]. The presence of sequential processes complicates the analysis of the experimental data because these processes change both the isotope yields and the energy spectra of the reaction products.…”

“…It means that the direct-transfer (or breakup-fusion) mechanism dominates over the pure projectile breakup. Sequential processes [4,[6][7][8][9] also take place in the reactions. High-excited heavy projectile-like fragments, formed by the direct transfer as a first step, undergo a sequential decay mainly by alpha-particle emission which is due to its low threshold.…”

“…Apparently, the shape of the spectrum of the fragments which are due to the direct-transfer process can be obtained from the high-energy part of the spectrum. The group from Hahn-Meitner Institute [6][7][8][9] has measured the multiplicity of the emitted neutrons in coincidence with the fragments to separate the breakup contributions from the spectra. The analyses of the coincidence data, however, are complicated due to the mixing of a part of the direct-transfer component of the neutron-multiplicity distribution corresponding to the high-energy tail of the fragment spectrum with the breakup component.…”

“…In Ref. [9] the decomposition of the multiplicity distributions is based on an "intuitive" assumption about a symmetric shape of the neutron-multiplicity peak which corresponds to the direct-transfer component of the spectrum. The shape of the peak, however, is closely related to the shape of the fragment spectrum which is asymmetric.…”