Time-Dependent Description of Reactions with Weakly Bound Nuclei 8 Li, 8 B
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-Dependent Description of Reactions with Weakly Bound Nuclei 8Li, 8B V. V. Samarina, b, * a
Joint Institute for Nuclear Research, Dubna, Moscow oblast 141980 Russia b Dubna State University, Dubna, 141982 Russia *e-mail: [email protected] Received March 2, 2020; revised April 15, 2020; accepted April 27, 2020
Abstract—A numerical solving of the time-dependent Schrödinger equation is used to investigate the dynamics of breakup reactions and nucleon transfer at energies above the Coulomb barrier. The evolution of the wave functions of an outer weakly bound neutron of 8Li nucleus and a proton of 8B nucleus in collision with a 28Si nucleus is studied. The cross sections of outer nucleon stripping due to transfer and breakup were calculated. DOI: 10.3103/S1062873820080262
INTRODUCTION Reactions with the participation of such light weakly bound nuclei as the neutron-rich 11Li nucleus and the proton-rich 8B nucleus provide additional opportunities for investigating the properties of nuclei at the boundaries of stability. In grazing collisions, the outer nucleons of the projectile nucleus can be captured by the target nucleus (transfer reactions) or released (breakup reactions). A generalized model with the separation of all nucleons into those that form strongly bound core and outer (valence) nucleons can be applied to weakly bound nuclei. The energies of separation for a nucleon from a core substantially exceed those for a valence nucleon. Examples of such systems with one outer nucleon are mirror nuclei 8В (core {7Be} and a proton with an energy of separation of 0.136 MeV [1]) and 8Li (core {7Li} and a neutron with an energy of separation of 2.032 MeV [1]). The energy of proton separation for a 7Be nucleus and the energy of neutron separation for a 7Li nucleus are 5.607 and 7.251 MeV, respectively. The possibility of considering the behavior of one outer nucleon in the field of two force centers, a permanent (frozen) target nucleus and the core of a projectile nucleus, simplifies theoretical descriptions of the transfer and breakup channels in nuclear collisions. The density distribution for weakly bound outer nucleons differs notably from the density of core nucleons. The part of the distribution of weakly bound nucleons extending beyond the core is called the halo [2]. Reactions with weakly bound nuclei 8B, 8Li were studied in [3–7]. The following nuclei were used as targets: 58Ni (8B + 58Ni
reaction) [3], 12С (8Li + 12С reaction) [4], 209Bi (8Li + 209Bi reaction) [5], 28Si (8Li + 28Si reaction) [7]. The use of 28Si target nuclei ensures better experimental conditions, since the target and detector can in this case be combined [7–10]. In this work, we calculate the cross sections of outer nucleon loss due to transfer and break-up in grazing collisions 8Li + 28Si and 8B + 28Si. A characteristic value of energy in the laboratory system for a projectile nucleus of 10 MeV/nucleon is close to the average kinetic energy of an outer nucleon [8]. At lower energies the average nucleon velocity is higher than the relative veloc
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