Fast emission of?-particles in deep-inelastic36Ar+197Au collisions

Abstract

Angular and energy correlations between e-particles and deep-inelastic projectile-like fragments were measured for the system a6Ar+ *97Au at ELa b = 380 MeV. At most half of the coincident events can be attributed to statistical emission of e-particles from the fully accelerated projectile-like fragments. The remainder of the events may be due to direct emission during the first 10-22 s of the scattering process and to preequilibrium processes taking place within some 10 21 s.During the last few years many experiments have been performed with the aim to clarify the reaction mechanisms of the production of fast light particles in heavy-ion collisions [1,2]. For the majority of the cases studied the underlying reaction mechanisms turned out to be evaporation from fully accelerated fragments. In a recent study of the 14N + 159Tb system [2], in addition to the sequential-decay component an "uncorrelated" component was attributed to inelastic breakup. In a previous paper [3] we presented the results of the analysis of quasi-elastic 36Ar + 197Au collisions. In that system, almost all of the coincident events could be understood in terms of the statistical decay of long-living (10-17 s) levels of the emitting fragments. The same interpretation was found to be valid for quasi-elastic ZONe+ 197Au and 2~ + 4~ collisions at EL,b = 290 MeV [4]. In those systems the conclusions were even more stringent, since in the spectrum of relative energies between the outgoing coincident fragments (for example 160 + cQ well-known states of/ONe were observed. In contrast to our previous investigations, this paper * Also Fachbereich Physik der Freien Universit/it Berlin, Germany ** Now at LASL, Los Alamos, NM 87545, USA deals with deep-inlastic projectile-like fragments accompanied by coincident a-particles. The experiment was performed at the VICKSI accelerator of the Hahn-Meitner-Institute and is described in [3]. The heavy ions were detected at 0H.I= 37.5 ~ by means of solid-state E-A E telescopes and the e-particles were detected in the angular range 8 ~ 165 ~ on both sides of the beam using solid-state E-AE telescopes at large angles and a proportional-counter (AE) -scintillator-photomultiplier (E) telescope at forward angles. The velocity plot shown in Fig. 1 a displays the spectrum of the e-particles detected in coincidence with deep-inelastic projectile-like heavy ions in the range of atomic numbers 14<Z<18. The velocity plots for each of these atomic numbers all look alike within our statistical accuracy. Therefore, no information is lost or smeared out by the summation over the indicated range of Z-values. We note that the coincident cross section peaks at forward angles. At larger angles (0~ ~, 55 ~ the intensity has decreased by about the factor 4 and at backward angles (0,~140 ~ not shown) no events were observed at all. For the system under consideration the statistical emission of a-particles from a fully accelerated pro-0340-2193/82/0309/0049/$01.00

Incomplete deep-inelastic scattering in20Ne+197Au collisions at 20 MeV/nucleon

“…Qualitatively, the multiplicity of the non-sequential emission increases with the bombarding energy, as expected on basis of the reaction picture outlined above. Going, for instance, to the lower bombarding energies around 10 MeV/ nucleon the non-sequential component generally becomes so weak that only in few cases it could be detected [12,15,25] with some confidence after due consideration of the sequential-emission contribution. (There also remain open problems in particular on the quantitative level.…”

“…In recent years a considerable amount of experimental data on e-deep-inelastic-PLF correlations obtained in the energy range E/A > 10 MeV shows features which cannot be explained in terms of the sequential decay of the deep-inelastic ejectile [10][11][12][13][14][15]. The name incomplete deep-inelastic collision (IND-IC) has been used by some authors [14][15][16].…”

“…The name incomplete deep-inelastic collision (IND-IC) has been used by some authors [14][15][16]. Two simplified models of INDIC have been put forward.…”