Mass and velocity distributions have been measured for the evaporation residue and fusion-fission products from the ' 0+ Ca reaction at 214 MeV. Comparisons of Monte Carlo statistical evaporation simulations to the observed angle and mass dependences of the evaporation-residue velocity distributions were used to set limits on the maximum complete-fusion cross section and to extract information about the magnitude and character of incomplete-fusion processes. The extracted value of the complete fusion evaporation-residue cross section is discussed in the framework of previous results and existing models.

The evolution of the / quasicontinuum spectrum with neutron number has been investigated in the sequence of isotopes ,52 < 154 > 156 £)y. The three nuclei display a pronounced collective E2 component. In l54 Dy this component shows a splitting into two distinct parts, signifying a structural change along the / cascade above the yrast line. The E2 and statistical components are reproduced in simple /-cascade calculations; in 152 Dy and 156 Dy only rotational bands are included, whereas in 154 Dy additional vibrationlike transitions are required to reproduce the two E2 peaks.

Fission yields for the Ni+ Zr reaction at laboratory energies between 240 and 300 MeV have been measured. "Elastic scattering" angular distributions were also obtained and used to deduce the generalized total reaction cross sections. The competition between fission and light-particle evaporation from the compound nucleus is well reproduced by statistical-model calculations. However, the calculated neutron multiplicities for this reaction are larger than those previously measured. Possible reasons for this discrepancy are discussed.

The energy dependence of the one-and twoparticle transfer reactions 9~ 170)89Zr, 9~ 15N)9iNb and 9~ 14C)9ZMo was studied at bombarding energies of 80 MeV, 138.2 MeV and 194.4 MeV. A comparison with one-step DWBA calculations shows good agreement for the one-particle transfers over the whole energy range. For the two-proton transfer reaction (160, 14C) the discrepancies between experiment and theory are large with an exponential decrease towards higher energies. Current theories are unable to describe this behavior. PACS: 25.70.Cd; 24.50. + g IntroductionHeavy-ion induced transfer reactions have so far hardly been used as a spectroscopic tool in nuclear structure studies. Initial expectations about the possibility to study multi-particle transfer reactions inaccessible to light-ion induced reactions have not been fulfilled. Heavy-ion induced transfer reactions at energies in the vicinity of the Coulomb barrier are found to be strongly influenced by multi-step processes which are theoretically difficult to handle. The large variety of transfer reactions possible with heavy ions has therefore not yet been fully exploited.Two-particle transfer reactions present a good example. (3He, n) reactions have been studied extensively in the past [1,2], but the energy resolution available with neutron time-of-flight techniques puts severe restrictions on the usefulness of this reaction as a spectroscopic tool in studies of heavier nuclei [3]. Heavy-ion induced * Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday

In-beam y rays from excited states of the neutron-rich (T, 3) nucleus~C l have been identi6ed in a threefold coincidence experiment in which y rays and light charged particles were observed. The resulting decay scheme is presented, and implications for the structure of low-lying levels in~C 1 are discussed in light of recent data from charge-exchange and PMecay work. The ordering of levels would seem to be quite difkrent from the predictions of recent shell-model calculations.The most recent measurement of the mass of~C I and the first observation of excited levels of this exotic neutron-rich nucleus were by Fifield et al. ,' who used the

States in 154 Dy have been located up to 7*=48 + and their lifetimes measured. Marked structural changes occur along the yrast line with a transition from prolate to oblate shape, followed by an unexpected return to moderate collectivity at the highest spins. Structural changes with increasing energy above the yrast line are also observed.Rapid rotation may induce dramatic structural changes in some nuclei. The transitional nuclei, which lie in the regions between spherical and deformed nuclei, should be particularly susceptible to stresses arising from rapid rotation. Thus, properties of such nuclei provide a stringent test of nuclear models. The TV =88 isotones, which bridge the sudden change from oblate shapes for TV < 86 to prolate shapes for TV > 90, have been a fertile testing ground. They generally have slightly prolate shapes at low spins, but switch to oblate shapes at higher spins. 1 "" 3 Theory 2 accounts for this switch in terms of band termination, a process where the shape associated with a given configuration having initial prolate deformation changes until it reaches the oblate limit. This band-termination picture has so far been checked mainly by comparisons with the energy levels of yrast states of nuclei in the transitional region. For a more rigorous test of theoretical models it is important to measure both yrast and nonyrast levels and, particularly, to determine lifetimes, which provide a direct measure of collectivity. It is also of considerable interest for our understanding of nuclear structure to measure the properties of states at higher spin to ascertain if the oblate coupling scheme persists beyond the maximum spin which can be generated by the valence nucleons.With these motivations, we have identified levels in x lt^>y%% to very high spin (7*=48 + ) and have also measured the state and feeding lifetimes. The level scheme and B(E2) values confirm the previously observed prolate-to-oblate transition. 1,2 However, at the highest spins a feature not predicted by theory is observed: There is a return to collective behavior at / =40.High-spin states of 154 Dy were populated via the reaction 122 Sn( 36 S,4*) with a 165-MeV beam from ATLAS (Argonne Tandem Linac Accelerator System). Two types of targets ( 122 Sn enrichment > 92%) were used: a stack of four self-supporting foils which allowed the residues to recoil into vacuum, and a target evaporated on a Pb backing, in which the residues stopped in -2 ps. In each case, the total Sn thickness was -1 mg cm ~2. The decay /'s were detected with use of the Argonne-Notre Dame /-ray facility consisting of eight bismuth germanate Compton-suppressed Ge spectrometers, of which three were positioned at 34°, two at 90°, and three at 146° with respect to the beam direction. A central array of fourteen bismuth germanate hexagons, with a detection efficiency of 38% for 662-keV / rays, acted as a multiplicity filter. A total of 135xl0 6 true promptcoincidence events were obtained for the stacked target and 55 x 10 6 for the backed target. The very clean s...

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