Elastic, inelastic, and 1-nucleon transfer channels in the ${}^7\mathrm{Li}+{}^{120}\mathrm{Sn}$ system

Background: Simultaneous description of major outgoing channels for a nuclear reaction by coupled-channels calculations using the same set of potential and coupling parameters is one of the difficult tasks to accomplish in nuclear reaction studies.

Purpose: To measure the elastic, inelastic, and transfer cross sections for as many channels as possible in ${}^7\mathrm{Li}+{}^{120}\mathrm{Sn}$ system at different beam energies and simultaneously describe them by a single set of model calculations using fresco.

Methods: Projectile-like fragments were detected using six sets of Si-detector telescopes to measure the cross sections for elastic, inelastic, and 1-nucleon transfer channels at two beam energies of 28 and 30 MeV. Optical model analysis of elastic data and coupled-reaction-channels (CRC) calculations that include around 30 reaction channels coupled directly to the entrance channel, with respective structural parameters, were performed to understand the measured cross sections.

Results: Structure information available in the literature for some of the identified states did not reproduce the present data. Cross sections obtained from CRC calculations using a modified but single set of potential and coupling parameters were able to describe simultaneously the measured data for all the channels at both the measured energies as well as the existing data for elastic and inelastic cross sections at 44 MeV.

Conclusions: Non-reproduction of some of the cross sections using the structure information available in the literature which are extracted from reactions involving different projectiles indicates that such measurements are probe dependent. New structural parameters were assigned for such states as well as for several new transfer states whose spectroscopic factors were not known.

Figure 1

Schematic of experimental setup

Figure 2

Typical two-dimensional gain-matched spectrum showing the outgoing projectile-like fragments at ${\theta }_{\mathrm{lab}}={60}^{\circ }$.

Figure 3

Typical 1D spectrum showing $Q$-value distribution of states identified in (a) elastic and inelastic scattering, (b) $1n$ stripping transfer, and (c) $1p$ stripping transfer processes at ${\theta }_{\mathrm{lab}}={60}^{\circ }$.

Figure 4

Experimental cross section and CRC calculation for the elastic channel (relative to Rutherford).

Figure 5

Experimental cross sections (open circles) and respective calculations (solid lines) for inelastic scattering processes in ${}^7\mathrm{Li}+{}^{120}\mathrm{Sn}$ system at 28 MeV for (a) quadrupole excitation in ${}^7\mathrm{Li}$, (b) quadrupole excitation in ${}^{120}\mathrm{Sn}$, (c) mutual quadrupolar transitions in ${}^7\mathrm{Li}$ and ${}^{120}\mathrm{Sn}$, and (d) octupole excitation in ${}^{120}\mathrm{Sn}$. The corresponding experimental data (filled circles) and calculations (dashed lines) for 30 MeV are shown in panels (e), (f), (g), and (h), respectively. Dotted lines in panels (e)–(h) represent calculations for $E_{\mathrm{beam}}=30$ MeV using modified but equal Coulomb and nuclear deformation lengths.

Figure 6

Experimental cross sections (open circles) and respective CRC calculations (lines) for $1n$ transfer process $\left({}^7\mathrm{Li},{}^6\mathrm{Li}\right)$ at 28 MeV for different excitations of the recoiling nucleus are shown in panels (a)–(d). Solid lines represent total contributions from experimentally unresolved multiple states with individual cross sections shown by dotted, dash-dot-dotted, and dashed lines. The corresponding experimental data (filled circles) and calculations (lines) for 30 MeV are shown in panels (e)–(h). The structural information of the states included in the model calculations for each centroid energy are listed in Table 3.

Figure 7

Experimental cross sections (open circles) and CRC calculations (lines) for $1p$ transfer process $\left({}^7\mathrm{Li},{}^6\mathrm{He}\right)$ at 28 MeV for different excitations of the recoiling nucleus are shown in panels (a)–(g). Solid lines represent total contributions from experimentally unresolved multiple states with individual cross sections shown by dotted and dash-dot-dotted lines. The corresponding data (filled circles) and calculations (lines) for 30 MeV are shown in panels (h)–(n). The structural information of the states included in the model calculations for each centroid energy are listed in Table 3.

Figure 8

Coupling scheme used for the CRC calculations by fresco.

Figure 9

Available data at $E_{\mathrm{beam}}=44$ MeV, for (a) elastic scattering and (b) inelastic scattering corresponding to the 478-keV excitation of ${}^7\mathrm{Li}$ from Ref. [32] and (c) inelastic scattering corresponding to the 1.17-MeV state in ${}^{120}\mathrm{Sn}$ taken from Ref. [33]. The lines represent the model calculations.