One-neutron stripping processes to excited states of the ${}^6\mathrm{Li}+{}^{96}\mathrm{Zr}$ reaction at near-barrier energies

We report the measurement of one-neutron stripping to excited-state cross sections from the weakly bound projectile ${}^6\mathrm{Li}$ to the ${}^{96}\mathrm{Zr}$ target at near-barrier energies by the online $\gamma$-ray spectroscopy method. Transitions of the ${}^{97}\mathrm{Zr}$ nucleus were clearly identified by $\gamma \text{−}\gamma$ coincidences. This cross section was found to be much smaller than the previously reported complete-fusion cross section for this system at energies above the barrier, whereas it becomes of the same magnitude around the Coulomb-barrier energy. No evidence of two-neutron transfer was found. We also performed coupled reaction channel calculations for the one-neutron stripping process. The calculation results are discussed.

Figure 1

The partial-level diagram of ${}^{97}\mathrm{Zr}$ [57]. The energy is in units of keV.

Figure 2

(a) Typical online $\gamma$-ray spectrum depicting the $\gamma$ lines of the $1n$ stripping residue nucleus ${}^{97}\mathrm{Zr}$ in the ${}^6\mathrm{Li}+{}^{96}\mathrm{Zr}$ system at the bombarding energy of 28 MeV. Panels (b)and (c) show the coincident spectra of the 1103.1 and 1400.1 keV transitions [57, 58, 59], respectively.

Figure 3

Typical $\mathrm{\Delta }E\text{−}E$ spectrum showing the light charged particles produced in the reaction ${}^6\mathrm{Li}+{}^{96}\mathrm{Zr}$ at the bombarding energy of 28 MeV and at ${65}^{\circ }$ with respect to the beam direction. Alpha particles, deuterons, and protons are clearly identified.

Figure 4

Measured complete fusion and direct plus two-step $1n$ stripping to excited-state cross sections corresponding to 1103.1 and 1400.1 keV energies for the ${}^6\mathrm{Li}+{}^{96}\mathrm{Zr}$ system at near- Coulomb-barrier energies.

Figure 5

Coupling scheme for the projectile overlaps.

Figure 6

Coupling scheme for the target overlaps.

Figure 7

Comparison of experimental data with CRC calculations for the ${}^6\mathrm{Li}+{}^{96}\mathrm{Zr}\to {}^{97}\mathrm{Zr}^{*}+p+\alpha$ reaction.