Weak Gamow-Teller (GT) responses for low-lying states in ${}^{71}\mathrm{Ga}$ are crucial for studying low-energy solar neutrinos and the Ga anomaly, i.e., the possible transition to the sterile state. The structures for the ground state, the first excited state, and the second excited state are evaluated for the first time using the experimental electron capture rates, the experimental charge exchange reaction (CER) rates corrected for the tensor-interaction effect, and the theoretical interacting shell model (ISM) calculations. On the basis of these experimental and theoretical results, the neutrino responses for them are evaluated. The contributions from the two excited states to the solar and ${}^{51}\mathrm{Cr}$ neutrinos are found to be $4.2\pm 1.2\%$ of that for the ground state. This is slightly larger than the ISM values but a little smaller than the CER values without corrections for the tensor interaction effect. The Ga anomaly is far beyond the uncertainty of the obtained nuclear responses. The present work shows for the first time the way to evaluate the tensor contributions on the basis of the EC/$\beta$ and CER experiments and the ISM calculations.

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• Charge-exchange reactions
• Electron & muon capture
• Sterile neutrinos
• 59 ≤ A ≤ 89
• Shell model