Weakly populated multinucleon transfer channels studied with a new time-of-flight magnetic spectrometer

Abstract

A new time-of-flight spectrometer with magnetic quadrupoles has been developed. Its high detection efficiency and resolution allows one to identify ions produced with low cross sections in a binary reaction. The study of multinucleon transfer channels in the system 48 Ca + 124 Sn revealed a large drift of the experimental total cross sections with respect to calculations which include independent single nucleon transfer modes. Incorporating pair and α-cluster channels into theory accounts, at least qualitatively, for the discrepancies. New data coming from the study of 64 Ni + 238 U show the striking presence of −1α, −2α and −3α channels, supporting once more the idea that cluster degrees of freedom must be considered in a correct description of the reaction mechanism.

Systematic investigation of weakly populated multinucleon transfer channels

“…For channels involving protons, the presence of maxima in the Z = 2 6 ; 24; 22 isotope distributions for the nuclei 60 Fe, 56 Cr and 52 Ti, respectively, suggested, in a preliminary analysis [3], possible -cluster effects similar to those already found in the experiment with the 48 Ca beam [13]. However, the interpretation is probably quite different, since other mechanisms come into play.…”

“…In the 64 Ni+ 238 U system [3], studied with the Tandem + ALPI accelerator complex of LNL at E lab =390 MeV, we could observe a very large number of transfer channels, in the pick-up and stripping of both neutrons and protons. In particular we see events corresponding to the pick-up of 6 neutrons and to the stripping of 6 protons and 6 neutrons, with cross-sections down to ' 50-100b/sr.…”

“…In recent high-resolution experiments [1][2][3][4][5] in the field of heavy-ion reactions, performed with time-of-flight and magnetic spectrometers at bombarding energies close to the Coulomb barrier, one could identify transfer channels produced in binary collisions, up to six neutron pick up and 6 proton stripping. Such measurements open new possibilities for detailed investigations of different physical aspects : 1) interplay between single nucleon transfer modes and more complex degrees of freedom [6][7][8][9] (e.g.…”

“…Such measurements open new possibilities for detailed investigations of different physical aspects : 1) interplay between single nucleon transfer modes and more complex degrees of freedom [6][7][8][9] (e.g. pairing and cluster effects) , 2) transition from quasi-elastic to deep-inelastic processes [10], 3) coupling effects with other reaction channels [11] (e.g. subbarrier fusion), 4) production of (neutron-rich) nuclei not accessible by other means [12].…”

“…In the present paper we will present the results obtained for the two systems 48 Ca+ 124 Sn [13] and 64 Ni+ 238 U [3], recently measured at LNL. These studies are part of the experimental program which is being pursued at LNL with the time-of-flight magnetic spectrometer PISOLO, where a combination of high efficiency and high resolution for Z and A allows one to identify the heavy ions produced in binary reactions at energies down to ' 1 MeV/a.m.u.…”