0000000000110742
AUTHOR
A. Trzcińska
Examination of the influence of transfer channels on the barrier height distribution: Scattering of 20Ne on 58Ni, 60Ni, and 61Ni at near-barrier energies
Background: It was suggested that the shape of the barrier height distribution can be determined not only by strong reaction channels (collective excitations) but also by weak channels such as transfers and/or noncollective excitations. Purpose: The study of the barrier height distributions for the 20Ne + 58,60,61Ni systems requires information on transfer cross sections at near-barrier energies. Methods: A measurement of the cross sections for various transfer channels at a backward angle (142 degrees), at a near-barrier energy was performed. Identification of products was based on time-of-flight and E-E methods. A measurement of the angular distribution of α stripping in the 20Ne + 61Ni s…
Effects of weakly coupled channels on quasielastic barrier distributions
Heavy-ion collisions often produce fusion barrier distributions with structures displaying a fingerprint of couplings to highly collective excitations. Similar distributions can be obtained from large-angle quasielastic scattering, although in this case, the role of the many weak direct-reaction channels is unclear. For $^{20}\mathrm{Ne}+^{90}\mathrm{Zr}$, we have observed the barrier structures expected for the highly deformed neon projectile; however, for $^{20}\mathrm{Ne}+^{92}\mathrm{Zr}$, we find significant extra absorption into a large number of noncollective inelastic channels. This leads to smearing of the barrier distribution and a consequent reduction in the ``resolving power'' o…
Transfer cross sections at near-barrier energy for the 24Mg + 90,92Zr systems
We have tested the hypothesis that for systems 24Mg + 90,92Zr, the shape of the barrier height distribution is not influenced by transfers processes. The experiment was performed using the ICARE detector system at the Warsaw Cyclotron. Having measured the transfer cross sections of the near-barrier collisions of 24Mg + 90,92Zr, we have found them to be roughly half of the value obtained for the 20Ne + 90,92Zr systems. From that observation, we conclude that in the 24Mg + 90,92Zr case, the leading cause of washing out the barrier distribution structure is the partial dissipation of relative kinetic energy into the non-collective excitation of the system. peerReviewed
Weak channels in backscattering of20Ne onnatNi,118Sn, and208Pb
To further our understanding of the influence of weakly coupled channels on the distribution of Coulomb barrier heights, we have measured transfer cross sections for ${}^{20}$Ne ions backscattered from ${}^{\mathrm{nat}}$Ni, ${}^{118}$Sn, and ${}^{208}$Pb targets at near-barrier energies. The $Q$ value spectrum in the case of ${}^{208}$Pb target has been determined too. The transfer channels appear to be especially important for ${}^{208}$Pb, whose double-closed-shell nature leads to a relatively low level density for noncollective inelastic excitations.
Examination of the influence of transfer channels on the barrier height distribution: Scattering ofNe20onNi58,Ni60, andNi61at near-barrier energies
Background: It was suggested that the shape of the barrier height distribution can be determined not only by strong reaction channels (collective excitations) but also by weak channels such as transfers and/or noncollective excitations.Purpose: The study of the barrier height distributions for the $^{20}\mathrm{Ne}+\phantom{\rule{0.16em}{0ex}}^{58,60,61}\mathrm{Ni}$ systems requires information on transfer cross sections at near-barrier energies.Methods: A measurement of the cross sections for various transfer channels at a backward angle (142 degrees), at a near-barrier energy was performed. Identification of products was based on time-of-flight and $\mathrm{\ensuremath{\Delta}}E\text{\ens…
Smoothing of structure in the fusion and quasielastic barrier distributions for the20Ne+208Pb system
We present simultaneously measured barrier distributions for the ${}^{20}$Ne $+$ ${}^{208}$Pb system derived from large-angle quasielastic scattering and fusion, in the latter case by means of the detection of fission fragments. Both distributions turned out to be smooth, in spectacular disagreement with the results of standard coupled-channels calculations. Namely, they do not posses the strong structure expected from coupled-channels calculations, even if apparently they take into account explicitly all relevant strong couplings. This points to the importance of weak channels, i.e., transfer reactions and scattering connected with noncollective excitations.