Background: Lithium is of broad interest in nuclear astrophysics, fusion energy research, and nuclear technology. From a theoretical perspective, the nucleus ${}^7\mathrm{Li}$ presents a remarkable challenge, as its bound and resonant states can exhibit contributions from both the ${}^4\mathrm{He}$ $+$ ${}^3\mathrm{H}$ cluster configuration and configurations involving a neutron or proton coupled to a ${}^6\mathrm{Li}$ or ${}^6\mathrm{He}$ core, respectively.

Purpose: We aim to achieve a unified ab initio description of bound-state and continuum properties of ${}^7\mathrm{Li}$ by explicitly including simultaneously the coupled mass/charge partitions ${}^4\mathrm{He}$ $+$ ${}^3\mathrm{H}$, ${}^6\mathrm{Li}$ $+$ $n$, and ${}^6\mathrm{He}$ $+$ $p$. Specifically, we investigate the effect of interpartition coupling on the spectrum of ${}^7\mathrm{Li}$ and calculate cross sections for the ${}^6\mathrm{Li}$($n,p){}^6\mathrm{He}$, ${}^6\mathrm{He}$($p,n){}^6\mathrm{Li}$, and ${}^6\mathrm{He}$($p,t){}^4\mathrm{He}$ reactions.

Method: We employ the no-core shell model with continuum for the first time in a calculation that couples three mass/charge partitions of the aggregate nucleus ${}^7\mathrm{Li}$, using a chiral nucleon-nucleon interaction as input.

Results: The calculated spectrum reproduces all the experimentally observed states of ${}^7\mathrm{Li}$ in the correct order and predicts additional resonances. The calculation also reproduces the overall energy dependence of the ${}^6\mathrm{Li}(n,p){}^6\mathrm{He}$ cross section. Improved agreement with measured cross sections is obtained after phenomenological adjustment of resonance energies.

Conclusions: The present results show that coupling the relevant mass/charge partitions is important for a consistent description of the ${}^7\mathrm{Li}$ spectrum and reaction cross sections, and offers a useful framework for interpreting existing data and guiding future measurements.

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• Charge-exchange reactions
• Cluster models
• Elastic scattering reactions
• Energy levels
• Models & methods for nuclear reactions
• Nuclear many-body theory
• Nuclear reactions
• Nuclear structure & decays
• Nucleon induced nuclear reactions
• Resonance reactions
• 6 ≤ A ≤ 19
• Ab initio calculations