[en] Excitation functions and angular distributions for the ¹²C(α,⁸Be)⁸Be reaction were measured for Esub(α)=17-33MeV. Only broad structures were observed, except for a narrow resonance at Esub(α)=22-30MeV. Total an L-partial cross sections are deduced from the angular distributions. Below Esub(α)=20MeV no J=8 resonance was found. For higher energies and L=8 contribution appears, increases gradually, and becomes dominant at and above Esub(α)=23MeV. A tentative interpretation of the behavior of ¹²C(α,⁸Be)⁸Be partial cross sections is given in the framework of the Hauser-Feshbach formalism

[en] The MultiWire Proportional Chamber and the ion telescopes at the VIVITRON tandem accelerator are described and their specifications are given. The document consists of transparencies presented at the workshop, text is missing. (K.A.) 17 figs., 1 tab

[en] This study was motivated by reports of the observation of ternary events in Kr- and Xe-induced reactions corresponding to the fast fission, or splitting, of projectile like products. The first of these reports, by Olmi et al., emphasized indirect evidence obtained from inclusive data from the reaction ⁸⁶Kr + ¹⁶⁶Er at 12.1 MeV/u. It was argued that the observed drift to low-Z products as a function of increasing energy loss could not be accounted for by charged-particle evaporation since the observed yield of charged particles was too low. It was concluded that the distribution of projectile fragments reflected an admixture of ternary events. More direct evidence for this hypothesis was presented by measurements of both projectile fragments, which indicated that relatively little energy loss is involved in the first step of the reaction and little charge transfer takes place prior to fission. The present study was intended to determine if such three-body events also occur in reactions with lighter projectiles to establish the extent of charge transfer and energy loss in the first step of the reaction. Results and preliminary conclusions are presented for reactions between ⁵⁸Ni nuclei at 15.1 MeV/u and ⁵⁸Ni reactions with mylar

[en] To see whether Molecular Resonances may be observed for A>32 systems, the ¹⁶O + ²⁴Mg reaction was investigated in the 17 to 31 MeV (CM) energy range. Despite the broad structure behavior of the ²⁴Mg + ¹⁶O outgoing channels, several rather narrow (GAMMA/sub tot/less than or equal to 500 keV) correlated resonances were observed for the ²⁸Si + ¹²C channels at backward angles. The angular distributions of two of these resonances at E/sub CM/ = 21.6 MeV and 28.0 MeV show J/sup π/ = (15^-) and (21^-), respectively. 1 reference

[en] The ¹²C(α,⁸Be)⁸Be reaction has been studied in the energy range E/sub alpha/ = 27--33 MeV. Analysis of angular distributions measured from E/sub alpha/ = 12.5 MeV to 33 MeV allows the extraction of the total cross section corresponding to the dominant l. Hauser--Feshbach calculations may explain the large structures observed

[en] The present study was intended as a search for sequential fission of projectilelike fragments for reactions induced by intermediate-mass heavy ions. The objective was to determine the fission probability as a function of excitation energy or energy loss in the first step of the reaction. The inclusive charge distributions measured with the large-area ionization chamber for reactions of ⁵⁸Ni + ⁵⁸Ni at 15.3 MeV/u were found to be dominated by products with Z < 28. Very little yield was observed for nuclei with charges greater than that of the projectile. It has been shown that most of the shift toward lighter products is consistent with the effects of equilibrium evaporation. At the largest calculated energy losses, the inclusive charge distributions were found to be slightly asymmetric due to an increasing component of fragments with half or less of the projectile charge. These light fragments were observed to have much broader angular distributions than the corresponding heavier fragments of the same energy loss. These observations from the inclusive measurements already suggest the occurrence of sequential fission of the projectilelike fragment. More conclusive evidence is obtained from coincidence measurements. Results are presented

No abstract available

[en] The present study was intended as a search for sequential fission of projectilelike fragments for reactions induced by intermediate-mass heavy ions. The objective was to determine the fission probability as a function of excitation energy or energy loss in the first step of the reaction. The experimental configuration was optimized for the detection of three-body sequential fission events over the full range of possible energy losses. The detector arrangement included a large-area ionization chamber which had two independent upper and lower halves, each capable of measuring the energy, E, and the energy loss, ΔE, of reaction products as well as their (x,y) position. A second detector was operated in coincidence on the other side of the beam axis. The inclusive charge distributions measured with the large-area ionization chamber for reactions of ⁵⁸Ni + ⁵⁸Ni at 15.3 MeV/u were found to be dominated by products with Z < 28. Very little yield was observed for nuclei with charges greater than that of the projectile. It has been shown that most of the shift toward lighter products is consistent with the effects of equilibrium evaporation. At the largest calculated energy losses, the inclusive charge distributions were found to be slightly asymmetric due to an increasing component of fragments with half or less of the projectile charge. These light fragments were observed to have much broader angular distributions than the corresponding heavier fragments of the same energy loss. These observations from the inclusive measurements already suggest the occurrence of sequential fission of the projectilelike fragment. More conclusive evidence is obtained from the coincidence measurements

No abstract available

[en] Backward-angle cross sections for the reactions ²⁴Mg(¹⁶O, ¹²C)²⁸Si(g.s.; 1.78 MeV) and ²⁴Mg(¹⁶O, ¹⁶O)²⁴Mg(g.s.; 1.37 MeV) were obtained for 17 MeV < or = E/sub c.m./ < or = 31 MeV, theta-bar/sub c.m./ approx. = 176⁰. The first reaction shows gross and fine resonant structures; the second shows mainly gross structures. Angular distribution measurements give L values of 15 and 21, respectively, at E/sub c.m./ = 21.6 and 28.0 MeV. The resonant gross structures for ²⁴Mg(¹⁶O,¹²C) ²⁸Si(g.s.) are governed by the entrance channel and are discussed from the shape-resonance point of view